Post on 06-Feb-2023
i
VARIATIONS IN THE SIZE AND TIME OF CLOSURE OF THE
ANTERIOR FONTANEL FROM BIRTH TO 24 MONTHS OF AGE IN
NIGERIAN CHILDREN IN PORT HARCOURT
A DISSERTATION SUBMITTED TO THE NATIONAL
POSTGRADUATE MEDICAL COLLEGE OF NIGERIA IN PARTIAL
FULFILLMENT OF THE REQUIREMENTS FOR THE AWARD OF THE
FELLOWSHIP OF THE COLLEGE IN PAEDIATRICS
BY
DR. OKORIE ELIZABETH-MARTHA C.
MBBS (NIG)
MAY 2013
iii
CERTIFICATION
The study reported in this dissertation was done by Dr (Mrs.) Okorie E-M C. under our
supervision. We have also supervised the writing of the dissertation.
.......................................
Supervisor
DR. P. I. OPARA
CONSULTANT PAEDIATRICIAN
UNIVERSITY OF PORT HARCOURT TEACHING HOSPITAL, PORT HARCOURT
.......................................
Supervisor
Prof. N.A. AKANI
CONSULTANT PAEDIATRICIAN
UNIVERSITY OF PORT HARCOURT TEACHING HOSPITAL, PORT HARCOURT
.......................................
Supervisor
DR . E.A D. ALIKOR
CONSULTANT PAEDIATRICIAN
UNIVERSITY OF PORT HARCOURT TEACHING HOSPITAL, PORT HARCOURT
iv
DEDICATION
To all Nigerian children, who are mis-managed, albeit with good intentions due to
parental ignorance of the normal evolution of the anterior fontanel.
To my family, for their understanding, prayers and support during the residency
programme.
To God Almighty, I owe Him everything.
v
ACKNOWLEDGEMENT
My gratitude goes first and foremost to God Almighty whose infinite grace and mercy
has brought me thus far.
I wish to acknowledge my Supervisors Dr. P. I. Opara, Dr N.A. Akani and Dr. E. A. D.
Alikor whose immense support and guidance enabled me to complete this work. I sincerely
appreciate them. I wish to thank Prof. K.E. O. Nkanginieme for his assistance in the course of
this dissertation. I sincerely thank Dr T. Okpere for her objective criticism of this book and
for her moral support throughout the residency programme.
I am grateful to the management of the University of Port Harcourt Teaching Hospital
(UPTH) and that of Braithwaite Memorial Specialist Hospital (BMSH), the staff of the
Special Care Baby Unit and the Post Natal Ward of UPTH, as well as the staff of the Well
Infant Clinics of both hospitals for their kind assistance in the course of this project.
I will not fail to acknowledge my Research Assistants Dr. Steve Ogboru, Dr. Ben Ishie,
Dr. Chinye Arinze, Dr. Denis Okoye, Dr. Calistus Chukwu, Dr Ine Briggs, Dr Ransome
Chukwu, Dr Mary Okpani, Dr. Peace Toritseju, Dr. Uju Azubogu, Dr. Alero Sagay, Dr.
Ifeyinwa Ugboma, Mr Ikechukwu Opara, Mr Henry Onyegbule, and Chinenye Onyegbule, as
well as Mr Jude of Souldek Consulting who taught and assisted me with the statistical
analysis./
I am grateful to my family and friends for their moral support and prayers.
vi
TABLE OF CONTENTS
TITLE AGE..................................................................................................................................i
DECLARATION.........................................................................................................................ii
CERTIFICATION......................................................................................................................iii
DEDICATION...........................................................................................................................iv
ACKNOWLEDGEMENT...........................................................................................................v
TABLE OF CONTENTS...........................................................................................................vi
LIST OFABBREVIATIONS....................................................................................................vii
LIST OF TABLES...................................................................................................................viii
LIST OF FIGURES.....................................................................................................................x
SUMMARY...............................................................................................................................xi
INTRODUCTION.......................................................................................................................1
REVIEW OF LITERATURE......................................................................................................4
JUSTIFICATION FOR THE STUDY......................................................................................39
AIMS AND OBJECTIVES.......................................................................................................41
SUBJECTS AND METHODS................................................................................................. 42
RESULTS..................................................................................................................................53
DISCUSSION............................................................................................................................86
CONCLUSION.........................................................................................................................92
RECOMMENDATIONS...........................................................................................................93
LIMITATIONS OF THE STUDY............................................................................................94
LINES OF FUTURE STUDIES................................................................................................95
REFERENCES..........................................................................................................................96
APPENDICES.........................................................................................................................105
vii
LIST OF ABBREVIATIONS
AF: Anterior fontanel
ANOVA: Analysis of variance
BMSH: Braithwaite Memorial Specialist Hospital
CT: Computerized Tomography
cm: Centimetre
GA: Gestational Age
hrs: Hours
IUGR: Intra Uterine Growth Retardation
IVH: Intraventricular Haemorrhage
MAX: Maximum
MIN: Minimum
mm: Millimetre
MRI: Magnetic Resonance Imaging
mo: Month
OFC: Occipito-frontal circumference
SCBU: Special Care Baby Unit
SD: Standard Deviation
UCH: University College Hospital
US: Ultrasonography
UPTH: University of Port Harcourt Teaching Hospital
WHO: World Health Organization
wks: Weeks
viii
LIST OF TABLES
Table I: Common causes of large fontanels ..................................................................31
Table II: Less common causes of large fontanels...........................................................32
Table III: Differential diagnosis of microcephaly............................................................35
Table IV: Causes of bulging anterior fontanel.................................................................37
Table V: Distribution of subjects by age and gender….....………………………….....54
Table VI: Distribution of newborns by gestational age and gender.................................55
Table VII:
Table VIII:
Distribution of the subjects by ethnic group....................................................56
Distribution of subjects by social class............................................................57
Table IX: Variation in mean AF sizes by postnatal age..................................................59
Table X: Variation of mean anterior fontanel sizes of newborns by gestational age
And gender......................................................................................................60
Table XI:
Table XII:
Dunnett’s multiple comparisons of differences in mean AF size between
different age groups.........................................................................................61
Mean, range and percentiles of AF in the study group...................................64
Table XIII: Relationship between mean anterior fontanel size, social class and age.........66
Table XIV:
Table XV:
Variation of mean AF size with ethnic group among the newborns................68
Variation of mean occipito-frontal circumference by age and gender.............70
Table XVI:
:
Variation of mean occipito-frontal circumference by gestational age
and gender........................................................................................................72
ix
LIST OF TABLES CONTD.
Table XVII: Dunnett’s multiple comparisons of differences in mean OFC between different
age groups…............................…………………………………………….........73
Table XVIII: Mean, range and percentiles of OFC in the study subjects....................................74
Table XIX: Correlation between the AF size, OFC and post natal age....................................77
Table XX: Relationship between postnatal age and closure of anterior fontanel......................... 79
x
LIST OF FIGURES
Fig.1: Lateral and superior views of the newborn skull showing the anterior and
posterior fontanels.............................................................................................................7
Fig. 2: Popich and Smith's method of measurement of the size of the anterior fontanel..........22
Fig. 3: Fleming and Pedroso's method of AF measurement.....................................................23
Fig. 4: Introduction of the tip of a finger to aid delineation of the extent of the fontanel in
the method of measurement of the AF by Davies et al..................................................24
Fig.5: Method of calculation of the area of anterior fontanel by Davies et al .......................24
Fig.6: Philips's Method of calculation of the area of the AF..................................................25
Fig.7: Scatterplot of variations of AF size by post-natal age and gender...............................62
Fig. 8: Variation in the 5th, 50th and 95th percentile of AF size with postnatal age................65
Fig. 9: Variation of mean AF size by social class…………………………………................67
Fig. 10: Scatterplot of variations of OFC size by postnatal age in males and females.............71
Fig. 11: Variations of the 5th, 50th and 95th percentiles of OFC with postnatal age..................75
Fig. 12: Scatterplot of the correlation between anterior fontanel size and occipito-frontal
circumference with postnatal age....................................................................................78
Fig. 13: Variation in percentage closure of anterior fontanel with postnatal age………..........80
xi
SUMMARY
The size of the anterior fontanel (AF) and the occipito-frontal circumference (OFC) are
useful indices of the rate of brain growth and ossification of the calvarium. They may also reflect
changes in intracranial pressure seen in different disease conditions and so form essential parts of
the neuro-developmental assessment of newborns and infants. However, there is a dearth of data
on AF size from cosmopolitan settings in Nigeria, particularly for infants between 12 and 24
months of age. The wide variation in the size of the AF underscores the need to establish local
reference standards for a given population. This study was done to address the gap in knowledge
on AF size in the South-South Geo-political Zone.
This was a cross-sectional observational and analytical study of 2895 consecutively
recruited children (313 neonates and 2582 infants) from two tertiary health institutions in Port
Harcourt. The AF size (determined by the modified method of Faix) and the OFC (determined by
the Student’s method), were measured in apparently healthy Nigerian children aged 48 hours to 7
days and at 6 weeks, 10 weeks, 14 weeks, 6 months, 9 months, 12 months, 18 months and 24
months of age.
The mean ± SD AF size for the newborns was 4.5 ± 1.7 cm while at 24 months the mean
AF size was 0.2 ± 0.7 cm. The mean ± SD OFC in the newborns was 35.8 ± 2.7 cm while at 24
months the mean ± SD OFC was 48.0 ± 2.3 cm. There was a statistically significant negative
correlation (r = -0.648, p = 0.000) between AF size and OFC with increasing post-natal age,
represented by the formula y = 14 - 0.265x, where y = AF size, and x = OFC.
Of the 2895 subjects, 667 (23.04%) had a closed AF. The number (%) with a closed AF was
9 (2.9%) among the 313 newborns and 288 (88.9%) of the 324 infants at 24 months of age. In
between these two 7/325 (2.2%), 76/321 (23.7%) and 273/321 (85.1%) had a closed AF at 6, 12
and 18 months of age respectively. The proportion of females (57.7%) with a closed AF was
xii
significantly higher than that of males (45.6%), (p< 0.0001). Among the newborns, there was a
statistically significant difference between the ethnic groups in the mean AF size (p < 0.05). The
largest AF size was observed among the Ogoni (6.4 ± 1.5 cm) while the Hausa/Fulani had the
least (3.0 ± 3.5 cm). However at 24 months, the Bini/Esan had the largest AF size (2.2 ± 1.8 cm)
followed by the Hausa/Fulani (1.4 ± 0.0 cm).
It is concluded that there is a strong negative correlation between the AF size and OFC.
This relationship, mathematically represented by the formula AF size = 14 - 0.265 x OFC can be
utilized to derive the expected AF sizes of infants from the OFC especially in a busy clinic setting
instead of physical measurement which is cumbersome and time consuming. This can assist in the
early identification of infants whose AF sizes deviate significantly from expected values for age
and who may benefit from further evaluation.
1
INTRODUCTION
Examination of the anterior fontanel (AF) forms an essential part of the neuro-developmental
evaluation of newborns and offers the physician the possibility of determining changes in
intracranial pressure and abnormalities of skeletal development in infancy.1-3 The word ‘fontanel’
originated from the Latin word ‘fonticullus’ and the old French Word ‘fontaine’ meaning little
fountain or spring.4-6 Fontanels are the fibrous membrane-covered gaps created where more than
two cranial bones are juxtaposed as opposed to sutures which are narrow seams of fibrous
connective tissues that separate any two flat bones of the skull.1,6,7
Variation in size is a key feature of the normal AF.1,3,8 The size of the AF is influenced by factors
such as gestational age, post-natal age and gender as well as by racial and environmental factors.8-
12 Faix,12 in 1982 reported larger AF size in Black neonates compared to their White counterparts
while some Researchers3,9,10,12 have documented increasing AF sizes with advancing gestational
age. In contrast to the findings by other Researchers,9,10,12-16 Mir and Wieslaw11 reported a
significant gender difference in the size of the AF. Kiesler and Ricer3 have put the average time of
closure of the AF at 13.8 months. In the study by Omotade et al14 at Ibadan Nigeria, 53% of the
subjects had a closed AF at 12 months of age.
The size of the anterior fontanel also varies widely between disease conditions and may be
abnormally large or small in certain metabolic, genetic, intra-uterine infections or endocrine
disorders.1,3,10,15,16 Palpating the AF of an infant for tension or depression can give a clue with
regards to the intracranial pressure and hydration status, respectively.1-3Ultrasonographic scan of
the brain through the anterior fontanel demonstrates a satisfactory view of the cerebral anatomy
and ventricular system.17 This can facilitate the early identification of intra cranial anomalies such
as intraventricular haemorrhage, hydrocephalus, cerebral oedema and loss of brain tissue in the
peri-ventricular region (later recognized as peri-ventricular leukomalacia [PVL]).17-19 Common
2
causes of large and or delayed closure of the AF include hydrocephalus, achondroplasia,
hypothyroidism, Down syndrome, raised intracranial pressure and rickets, while the commonest
cause of premature closure of the fontanel is craniosynostosis.4,8,15
There is a dearth of data on the size of the AF in Nigeria in particular and Africa in general
compared to Western nations.14 The range of normal values of various anthropometric parameters
including AF sizes have been established for Caucasian and Asian populations.20-22 In view of the
established racial differences in anthropometric parameters, which are genetically determined,
Caucasian figures may not be universally applicable. Hence there is need to obtain local values
from well-defined populations as a reference in the evaluation of the child with dysmorphic
features in order to avoid errors of classification due to differences arising from variations in the
normal range.1-3,11 Since the size of the AF also varies widely in various disease conditions,
knowledge of the range of normal sizes of the AF derived from a given community which can
then be regarded as reference values for that population is essential for early detection of such
diseases in order to ensure early treatment and a better outcome.
The available works by Nigerian Authors were carried out mainly in South-West Nigeria by
Ogunye et al,23Omotade,24 Omotade et al14 and, Adeyemo and Omotade9and in South Eastern
Nigeria by Ibe and Nwosu25 and Uzoukwu.26 Whereas Omotade et al14 and Ogunye et al 23
reported mean AF sizes of 4.0 cm ± 1.0 and 3.3 ± 2.0 cm among Yoruba neonates at Ibadan and
Ile-Ife respectively, Uzoukwu26 reported a mean AF size of 2.78 ± 0.82 cm among Igbo neonates
in Enugu. It does appear, therefore, that even within a given race, the size of the AF also varies
between the ethnic groups. However, the factors responsible for these differences are yet to be
determined. Moreover, while the study by Omotade et al14 was carried out in children from birth
to 12 months of age, the other Nigerian studies9,24,26 were limited to the neonatal period. Since the
AF may remain patent up to 24 months of age, reference values for AF sizes in Nigerian children
up to 24 months of age are necessary in order to identify deviations from normal in children from
3
birth to 24 months of age. To the best of this Researcher’s knowledge, no similar study has been
done in the South-South Geopolitical Zone nor did this Researcher come across any Nigerian
study on the size of the AF in children up to 24 months of age. This study was therefore carried
out to determine variations in the size and time of closure of the AF from birth to 24 months of
age in Nigerian children in Port Harcourt.
4
REVIEW OF LITERATURE
Overview of the anterior fontanel
At birth, the human baby has six fontanels – the anterior, the posterior, the two mastoid and the
two sphenoid fontanels.2,3,7,9 The diamond shaped AF is the largest and most significant for
clinical purposes.3,7 Useful information can be obtained from examining an infant’s AF as it offers
the clinician a window into an infant’s developing brain and general state of health.1-3,7,17
Studies3,12,16 have shown that the mean AF size in Black newborns is larger than published figures
for Caucasian and Asian populations, but at 12 months the reverse is the case. Due to the wide
variations in the size of the AF in health and disease, it is necessary to have local reference values
for a given population. Such reference values will help clinicians in the early diagnosis of
conditions associated with abnormal fontanels.3,12-15,18
Historical perspective
Interest in the size and time of closure as well as clinical correlation of the AF dates back more than
a century. Early observers28,29 had reported that the dimensions of the AF of the human skull
increases from the time of birth until about the age of 9 months, and that it is, as a rule, closed by
the age of 18 months.13, 28,29 Scammon and Adair 27 reviewing the literature challenged these
observations on the grounds that the subjects studied were European children of the poorer classes,
with many of them born prematurely and with many suffering from rickets. The Authors27 argued
that the observations did not necessarily apply to the 'better’ nourished and more rapidly growing
American children but they did not publish any figures to substantiate this view.
In 1978, Researchers18 at the University College London discovered a very important
clinical application of the AF when an ultrasound probe was accidentally placed over the AF
revealing an astonishing view of the ventricular system and cerebral tissues.18 This was found to
facilitate the early identification of intra-cranial anomalies such as intraventricular haemorrhage,
5
hydrocephalus, cerebral oedema and loss of brain tissue in the periventricular area later
recognised as periventricular leucomalacia.
Among the Igbo of Nigeria, a patent AF known as ’ntiwaisi ’is believed to be the underlying
cause in a child who is failing to thrive including neonates who had intrauterine growth
restriction.26 For this reason, different harmful unorthodox practices are employed in an attempt to
treat it. Famous among these is the topical application of clay based herbal concoction over the
AF predisposing the child to the risk of scalp infection and meningitis.26
Embryology of the fontanels
In foetal life, bone formation begins at the 4th week of intrauterine life.3,29 The flat bones of
the skull which form the borders of the fontanels are derived from mesenchyme originating from
the neural crest cells that differentiate directly into bone via intra membranous ossification.3,6,13,29
These flat bones are separated by narrow seams of fibrous tissue called sutures. Fontanels are
expansions of suture lines formed where more than two flat bones meet.
Anatomy of the newborn skull and the fontanels
The skull is made up of several layers, the neurocranium which forms the protective covering
surrounding the brain and the special sensory organs, the viscerocranium which forms the facial
skeleton, ear ossicles, hyoid bone, laryngeal and tracheal cartilages and certain processes of the
skull, and the dermatocranium which forms the large flat bones of the skull and face including the
frontal, occipital and squamous temporal bones.2, 3,7,13,29 The newborn skull, which appears to be
a single large bone is actually made up of one occipital, two parietal, two temporal and two frontal
bones, separated by fibrous connective tissue called “sutures.''3,4,7,13,29 A suture is considered
widened if its width is broader than 1centimetre (cm).30
There are four cranial sutures: 3,4, 29
(a) The metopic suture : This extends from the top of the head down the middle of the forehead,
6
towards the nose. The two frontal bone plates meet at the metopic suture.
(b) The coronal suture: This extends from either side of the anterior fontanel to the sphenoid
fontanel, between the frontal and parietal bones.
(c) The sagital suture: This lies in the median position between the parietal bones extending from
the AF to the posterior fontanel.
(d) The lambdoid suture: This extends across the back of the head. Each parietal bone plate meets
the occipital bone plate at the lambdoid sutures.
At birth there are six fontanels, namely:
(1) The anterior fontanel (AF) (Fig. 1): The AF is the largest of the fontanels and the most
important for clinical purposes.3,7,9 It is located in the antero-median position at the junction
of the coronal and sagital sutures. It has been described variously as “diamond-shaped'', and
''rhomboid-shaped''.3,7,13However, most Authors3,4,10,15 agree that it is an irregular
quadrilateral. There appears to be no significant difference between the length (anterior-
posterior distance) and the width (transverse distance) of the AF. 3,31,32
(2) The posterior fontanel (Fig.1): This is located in the postero-median position at the junction
of the sagital and lambdoid sutures. It is triangular in shape, and smaller than the AF with
most admitting only the tip of a finger.31
(3) The sphenoid fontanels (Fig.1): These are a pair of fontanels, located antero-laterally at the
junction of the parietal, temporal and frontal bones.4,13,17
(4) The mastoid fontanels (Fig.1): These are also a pair of fontanels located postero-laterally at
the junction of the parietal, squamous and occipital bones3,13,17
7
FIGURE 1: Lateral and superiorviews of the newborn skull showing the anterior and
posterior fontanels [Source - Kiesler J, Ricer3 R. The Abnormal Fontanel. Am Fam
Physician 2003; 67: 2547-52].
In the course of delivery, the sutures provide spaces between the developing bones which
permit changes of skull shape and size called “molding” 3,33 These changes aid delivery through
the birth canal and usually resolve by three to five days of life.2,13 The fontanels allow for rapid
growth of the brain during infancy. Growth of the cranium is triggered by brain growth, two thirds
of which occur by two years of life, and with the exception of the metopic sutures between the
frontal bones, the sutures remain open until brain growth ceases in the second decade of
life.3,13The size of the fontanels is therefore influenced by brain growth, dural attachments, suture
development and osteogenesis3,34
Size of the anterior fontanel
As pointed out by various researchers,3,8,9,15variation in size is a key feature of the AF. By
definition, the AF size is considered small or large when its size is 2 standard deviations (SD)
below or above the mean for a given population.8,24Popich and Smith8 studied 201 healthy term
Caucasian neonates and found a mean AF size of 2.1 ± 1.5 cm. These Researchers took their
8
measurements at 2 weeks of age which certainly obviates the effect of molding. However, at two
weeks, one wonders if the initial increase in the size of the AF in the first few months of life had
not commenced. A longitudinal study at 2 weekly intervals may be required to confirm this.
Srugo and Berger,35 measured AF size on the 3rd day of life in 303 Israeli neonates from different
ethnic groups and found a mean AF size of 2.06 ± 0.6 cm. This value is similar to that by Popich
and Smith; and based on the timing of the measurement at 3 days of life can be regarded as a
baseline value with which subsequent values could be compared. These figures agree with the
mean AF sizes of 2 x 2 cm2 and the 4 cm2 reported by Haslam2 in Philadelphia (USA), and
Philips32 in Hawaii, respectively. Pedroso et al36 found a mean AF size at birth of 1.77 cm among
Brazilian neonates. The study involved 33 neonates selected randomly from a total of 1066. The
actual age of the neonates at which the measurements were taken was not stated. The small
sample size in this study may have contributed to the small mean AF size reported.
Faix12 in America comparing mean AF size in Black and White term newborns, observed a
larger mean fontanel size in Black infants. The mean AF sizes in Black and White infants were
2.67 ± 0.70 cm and 3.08 ± 0.80 cm respectively. The reason for this difference was not clear
although it was thought to be due to better nutrition in the Caucasian newborns.
Chang and Hung31 studied 704 Chinese children aged 3 days to 12 months. Measurements
were taken at 3 days and at 1, 2, 4, 6, 9, 12, 18 and 24 months of age, respectively. The mean AF
size obtained at 3 days was 26.2 millimetres (mm) and 26.7 mm for females and males,
respectively. On account of the large population size studied as well as the timing of the
measurement in neonates at 3 days of life, it is reasonable to assume that these figures are
representative of Chinese neonates.
Mattur et al37 working among Indian children in Kampur reported a mean AF size of 3.37 ±
0.61 cm with a range of 2.2 to 4.5 cm. This is similar to the larger anterior fontanel size in Blacks
9
compared to Caucasians reported by Faix.12 Whether this reflects a closer genetic link between
people of Indian and African descent remains to be determined. It is also possible that this
similarity relates more to the nutritional status of children in both populations.
Ogunye et al23 at Ife studied 1,137 African neonates and found a mean AF size of 3.3 ± 2.0
cm with a range of 1.0 - 6.2.0 cm.23 These figures are similar to the American Negroid population,
and significantly higher than Caucasian values. Since the study criteria excluded known causes of
delayed closure of the AF, like achondroplasia, hypothyroidism and malnutrition, the Researchers
suggested that the relatively higher AF size could be due to delayed intrauterine osseous
maturation which may be a Negroid trait present as a ‘‘minor malformation'' and therefore a
Negroid genetic marker.23Adeyemo and Omotade9 in a study of 200 appropriate for gestational
age term neonates 12 - 48 hours old reported a range of AF size of 1.0 cm to 6.4 cm with a mean
of 4.0 cm. The mean AF size reported in their study9 was larger than previously reported Nigerian
figures,14 a fact which may be due to the exclusion of neonates who still had overriding cranial
bones (from excessive molding) at the time the measurements were taken. This point was not
considered by Ogunye et al.23 Omotade et al14 studied 337 infants aged 1 week to 12 months and
found that the mean AF size fell from 3.4 cm at birth to 0.8 cm at 10 -12 months.
Recently in Enugu, South-East Nigeria, Uzoukwu26 studied 316 Igbo appropriate for
gestational age neonates and found a range of fontanel size of 0.7 cm to 4.8 cm, with a mean size
of 2.78 ± 0.82 cm. The mean AF size obtained by Uzoukwu26 is significantly smaller than the
values reported by the other Researchers from the Western part of the country. The reasons for
these differences are not clear. It is interesting to note that the various studies from the South West
9,14,23,39 were conducted among predominantly Yoruba subjects while Uzoukwu26studied only
Igbo newborns. It is thus possible that there are ethnic differences even among people of the same
race. The role of environmental factors in modifying natural predisposition also remains to be
determined.
10
The posterior fontanel
This triangular shaped fontanel is smaller than the AF,6,7,29 (Fig.1). At birth, it has an average size
of 0.5± 0.22 cm in White infants and 0.70 ± 0.45 cm in Black infants.7,33 The posterior fontanel
may occasionally be closed at birth.3,13 At Ibadan, Adeyemo et al14 found a mean (SD) posterior
fontanel size of 1.4 ± 1.7 cm with a range of 0.0 cm to 5.5 cm. However, the posterior fontanel
was not palpable in 49.5% of the neonates studied. Ogunye et al23 at Ile-Ife, noted that posterior
fontanel was palpable in 45.4% of neonates. The sizes ranged from 0.5 cm to 4.0 cm with a mean
of 1.5 ± 0.8 cm. The anterior and posterior fontanels are commonly examined in routine clinical
practice. Consequently, some authors1,3 recognize them as the only fontanels on the skull of a
newborn. However, this is not so.
Other fontanels
These include the two mastoid fontanels and the two sphenoid fontanels. The mastoid and
sphenoid fontanels as described previously are located on each side of the skull. Although these
fontanels are regarded as less important clinically, some Researchers affirm that trans-fontanel
ultrasound scan of the brain through the mastoid fontanel gives a better view of infra- tentorial
structures. 13,18
Evolution of the fontanels after birth
The membranous bones of the skull enlarge by central resorption and by apposition of new
layers at the edges of the sutures. Ossification starts at about the 9th to 10th week gestational age,
and progresses with gestational age.1,3,26,31 At birth, a term baby's cranial vault is firm, with a
thickness of about 1 to 2 mm, but may depress to pressure along the borders of the bones
producing the popping in and out sensation of a ping-pong ball. This is due to a lag in ossification
at the peripheral portions of the bones.34 Growth of the cranium takes place in response to the
11
growth of the brain which it contains, two thirds of which occurs by two years but continues well
into the second decade of life.1,3.31
The size of the AF is influenced by brain growth, dural attachments, suture development
and osteogenesis1,3,9 It undergoes an initial phase of increase in size during the first few months of
postnatal life, and subsequently reduces after the first six months of life until eventual
closure.3,9,8,3,15,26 In certain cultures such as the Igbo of South-Eastern Nigeria, this initial increase
in an AF size known as 'ntiwaisi' is a major source of concern to parents who worry that it might
result in delayed closure. It is also sometimes mis-interpreted to be the underlying factor in a child
who is failing to thrive.26This is responsible for the wrong cultural practice of topical application
of clay-based herbal mixture on the scalp over the AF area which is thought to reduce the size and
hasten its closure.
In 1988, Chang and Hung31carried out a study of 704 Chinese subjects in Taiwan. They
stratified the subjects into 10 groups recruited from the Nursery and Well Baby Clinics. The ages
of the subjects at the time of measurement of the AF were 3 days, 1, 2, 4, 6, 9, 12, 18 and 24
months. The mean AF size at these ages were 26.2 mm, 24.9 mm, 25.7 mm, 20.2 mm, 14.9 mm,
11.5 mm, 10.2 mm, 13.0 mm and 12.1 mm, respectively. The initial increase in size of the AF
noted in other studies was not observed in this study possibly because the criteria for the selection
of the subjects were neither clear nor specific. However, the tendency for the AF to progressively
decrease in size after 6 months is in conformity with existing literature.2,3,6,8 The AF was closed in
5% of the subjects at six months of age, while at 24 months of age, 8% of the subjects still had
patent AF. It is difficult to conclude that this 8% with delayed closure of the AF are normal
variants since the selection criteria are unclear. No significant gender difference in the mean AF
size was observed. The mean age of closure of the AF of 14.5 months in males was similar to the
14.3 months in females.
12
In another study, Tan16 monitored the evolution of the fontanels till eventual closure in two
groups of normal Chinese infants with normal occipito-frontal circumferences (OFC). The first
group made up of 28 term neonates had widened cranial sutures (greater than 1cm) and large AF,
while the second group (the control) consisted of 60 term neonates with normal cranial sutures,
OFC and fontanels. Skull x-rays were taken of the entire group to exclude cranial anomaly. The
mean AF size of 2.05 ± 0.45 cm at birth showed an initial increase in the first few months of life
followed by a gradual decrease such that by 55 weeks and 18 months, the AF had closed in 25%
and 55% respectively while at 24 months, the AF had closed in all but one subject.16 No
significant relationship was observed between AF size and OFC, and there was no gender
difference with respect to AF size and time of closure.16 The mean AF size among the group with
wide cranial sutures (2.8 ± 0.4 cm) was significantly larger than that the control group (2.05 ±
0.45 cm, p< 0.01). However, similar pattern in terms of decrease in AF size and time of eventual
closure was observed. It thus appears that the width of the sutures in the absence of any pathology
does not influence the post-natal growth of the fontanels. Although skull X-ray may be useful in
excluding certain cranial abnormalities, there are many other anomalies of the cranium and
intracranial structures which influence the size of the AF but which cannot be excluded by the use
of skull x-rays alone. Also the exposure of these infants to X-rays would seem an unnecessary risk
since enough evidence abound in the literature of the adequacy of clinical method in the
assessment of anterior fontanel size.8,16,26,39
In another study of AF size in Kampur, India, among 445 children from the neonatal period
to 2 years of age, Mattur et al37 found a mean AF size of 3.37 ± 0.61 cm. The AF was closed in
40%, 70.4% and 91.3% at 12, 18, and 24 months, respectively. The mean AF size in these Indian
children was higher than that of their Western8,10,12, counterparts and those reported earlier in
some Indian studies40,41 but was similar to some other Indian studies,42,43 as well as values
obtained from studies among Black children.
13
The differences were attributed to regional variation and to poor socio-economic status of a
majority of the subjects while the delayed closure was attributed to under nutrition, a known
course of delayed closure of AF.16 This explanation appears contradictory when viewed against
the fact that the Researchers stated that the subjects had weight for age between the 3rd and the
95th percentiles, and that children with protein-energy malnutrition were excluded from the study.
Perhaps, the Authors did not adhere strictly to their exclusion criteria. Alternatively there may be
need to clarify further the definition of the term 'under-nutrition' said to be prevalent among the
populace.
In Zurich, Duc and Largo44 carried out a study on the size and time of closure of the AF in
111 term and 131 preterm infants. The AF size was taken as the average of both oblique
dimensions as opposed to the average of the antero-posterior and lateral dimensions used by other
Researchers.8,9,11,15,29 When gestational age was corrected for the preterm babies, the size of the
AF was similar in both groups. AF size was comparable in both male and female infants and
subsequent progressive decrease in AF size with age which followed the same pattern in both
term and preterm infants. The Authors found that the AF was closed in 1% of infants by three
months of age, 38% by 12 months and in 96% by 24 months of age. The 38% and 96% closures
in the study44 was similar to the 40% and 91% reported by Mattur et al37but different from the
55% closure at 24 months reported by Chang and Hang.31 Although AF closure occurred earlier in
boys compared to girls in the study by Mattur et al,16 the initial AF size was not predictive of the
time of final closure nor was there a significant relationship between AF size and OFC. In the
study of Brazilian children by Pedrosoet al,37 it was closed in 6-13% of subjects at 6 months and
in 27 % at 12 months. The study was limited to the first year of life but a 2 year follow-up study
found 98-100 % closed AF with a mean time of closure of 13.8 months.36
In a cross sectional study of 337 children at Ibadan, Nigeria, Omotade et al14 found a mean
AF size of 3.4 cm. This progressively decreased such that at 4-6 months, 7-9 months and 10-12
14
months, the AF sizes were 2.5 cm, 1.5 cm and 0.8 cm, respectively and was closed in 11% at 4-
6months and 53% at 10-12 months. Although the mean AF size in neonates in this study
waslarger than published figures for Caucasian and Chinese populations, at 12 months the mean
AF size of 0.8 cm in Nigerian children was smaller than the 1.2 cm and 1.7 cm for Caucasian and
Chinese children, respectively.31,44
The above figures reveal a faster rate of decline of the AF size in Nigerian children
compared to Caucasian and Chinese populations. The reason for the racial difference is not clear
considering the fact that the subjects in these studies were apparently healthy children. However,
it can be speculated that genetic and environmental factors or an inter-play between
environmental and genetic factors may be responsible. Hence the adoption of a single standard for
all races may not be appropriate. This underscores the need to generate population-specific
standards.
Closure of the AF is rare at birth, whereas the posterior fontanel is often closed at birth and
usually by 2-3 months of age.3 The median age of closure of the AF as documented by Kiesler and
Ricer3 was 13.8 months, whereas Haslam2 gave an average closure time of 18 months, with the
possibility of closure as early as 9-12 months. This shows that the time of closure of the AF also
varies widely.
Following the closure of the fontanels, the cranial bones become separated only by sutures.
This is so as to make allowance for brain growth which continues till about the end of the second
decade of life.3 Any deviation from this normal course of growth/closure of the fontanels may
most likely be a reflection of abnormalities and disease conditions.3 However, delayed closure of
the AF has been documented in an apparently healthy 4 year old Indian girl who otherwise had no
neurological or physical abnormality.45
15
Factors influencing the size and evolution of the anterior fontanel
The size of the AF is influenced by a number of factors, which include:
1. Gestational age
Although, Duc and largo44 reported no significant difference in AF sizes and eventual time of
closure between term and preterm infants, several studies9,10,26,45 have documented a strong
positive relationship between AF size and gestational age. The bones of the cranium develop in
membrane, and since fontanels are in essence expansions of the suture lines where these bones
meet, it seems logical to expect that if fontanel sizes reflect the rate of development and
ossification of the calvarium, they should be related to gestational age at birth.9
Davies et al,10 in studying such a relationship found that there was a progressive increase in
fontanel size with advancing gestational age, and a significant difference in the mean value of
fontanel size between preterm infants who were 28-32 weeks and term infants. However, similar
differences were not observed when the size of the fontanel of preterm infants who were born at a
gestational age of 33-36 weeks was compared to that of term infants.10 This study however, did
not take into account the increase in head circumference with advancing gestational age.
Malas and Sulak46 measured AF size in the foetal period and found a progressive increase with
advancing gestation which was most marked in the third trimester. Although these researchers
adopted different methods, their findings are in agreement with others showing that gestational
age does in fact influence the size of the AF in the more immature preterms but this influence
diminishes towards term. 9,10,26,45,46
Adeyemo and Omotade, 9 in a study of 250 Nigerian neonates, noted that the AF size was
positively correlated with gestational age. However, this correlation was further reduced when AF
was controlled for OFC. They also reported that AF size : OFC ratio did not differ significantly in
16
the various groups of preterm and term babies. This shows that the increase in AF size with
gestational age is independent of the OFC. However, the posterior fontanel size showed no linear
relationship with gestational age.9
II. Gender
Mir and Weislaw11 in a study of Arab infants found that there was a significant gender difference
in AF size with boys having a significantly higher AF size than girls at birth. However, the rate of
head growth was not significantly different in both males and females. In an earlier study,
Acheson and Eirlys47 had noted that despite the larger AF size at birth in boys, there was a
tendency for the AF to close earlier in boys. They concluded that skeletal maturation of the cranial
bones was geared differently from that of other bones of the body in which the female's lead in
skeletal maturation has been well documented.47 This finding may not be surprising since
preference for male children which was prevalent in that era may have resulted in better nutrition
for boys at the expense of the girl child leading to earlier skeletal maturation in male subjects.
More recent studies by Popich and Smith,8 and Tan,16 as well as Faix12 found no significant
difference in AF sizes between male and female newborn infants, although in the course of a 3
monthly follow-up, Popich and Smith8 found that the mean values for males tended to be higher
than those for females during the first six months. Pedroso et al37also noted that in the first year of
life, the AF was larger in boys than girls although the difference was not statistically significant.
The reason for the varying results is not clear. Similar comparative study may help to clarify the
presence or otherwise of gender difference in the evolution of the AF.
III. Race
Some researchers have documented variations in the size of the AF between different
races.11,12,15,23Popich and Smith8 in 1972 reported mean AF size of 2.6 cm in White neonates. At
the Duke University Medical centre, USA, Faix12 carried out a comparative study of 293 Black
17
and 73 White neonates. He found that the mean fontanel size was higher in Black neonates. These
infants had weight and head circumference between the 10th and 90th percentiles, respectively. The
values /obtained were 2.67 ± 0.70 cm for Whites and 3.08 ± 0.80 cm for Blacks. According to
Faix,12 the basis for this racial difference in fontanel size is unclear, but it is possible that
differences in nutritional status may be a factor.
In another study, Philips32 found no racial differences in AF size in a group of 63 Oriental,
White, and racially mixed term babies. However, all the subjects in the study were small for
gestational age which may have resulted from intra-uterine growth restriction, a factor known to
affect osseous maturation. This may account for the similarity in AF sizes in the different racial
groups.
Adeyemo et al,39 at UCH Ibadan found AF and posterior fontanel sizes that were 4.0 ± 1.0
cm and 1.4 ± 1.7 cm, respectively. These values are larger than those from Caucasian
populations. About 2/3 of the term neonates in Adeyemo et al's39study had AF sizes that were
larger than the upper limits reported for White American neonates by Popich and Smith.8 These
results are consistent with other works that have documented larger AF size in black neonates
compared to their Caucasian counterparts.12,23,32 Ogunye et al,23in a study of 1,137 African
neonates reported a mean AF and posterior fontanel sizes of 3.3 ± 2.0 cm and 1.5 ± 0.8 cm,
respectively. These values were significantly higher than published values for White American
neonates but similar to the AF sizes of American Negroid populations.12 Known causes of
abnormally large AF such as rickets, congenital hypothyroidism, achondroplasia, trisomies and
malnutrition were excluded by these Researchers.23 The reason for the larger fontanel size in
Black neonates therefore remains unclear. However, Ogunye et al23 has suggested that this may be
due to delayed intra-uterine osseous maturation which may be a Negroid trait present as a minor
malformation, and therefore a Negroid genetic marker.
18
Furthermore, from the various studies in Nigeria, there appear to be ethnic differences, as
the AF size reported by Uzoukwu26 among Igbo neonates in the South-East Nigeria is lower than
those found among Yoruba neonates in the South-West by Adeyemo and Omotade,9 Ogunye et
al,23Omotade et al,14 and Adeyemo et al 39respectively. The reason for these ethnic differences in
AF size in Nigerian children is yet to be determined. It is possible that it is multi-factorial involving
genetic, environmental and nutritional factors.
IV. Genetic influences
Ample evidence abound in the literature in support of the idea that the development of
facial and cranial features are both under genetic (autosomal and X-linked dominant and recessive
inheritance) and non-genetic influences.48 Poswillo48 described a model for mandibulo-facial
dysostosis which occurred after feeding pregnant rats high doses (75,000 to 100,000 IU) of
vitamin A on the 8th day of gestation. The resultant morphologic effect produced was similar to
that due to autosomal dominant gene for Treacher- Collins syndrome.48The typical physical
features include downward slanting eyes, micrognathia, conductive hearing loss, underdeveloped
zygoma, drooping of the lateral part of the lower eyelids, and malformed or absent ears.48 This
finding suggests that different factors produce the same teratogenic effect in different species.
Some Authors48 have, therefore, hypothesized that AF size may be under genetic influences
Melnick et al49 studied the limits of genetic variance in twin populations. Their subjects
were 94 monozygotic (MZ) and 187 dizygotic (DZ) twins. The Researchers also analyzed Black
and White infants separately. Their findings showed no significant chorion effect but the within
pair mean square estimates of genetic variance were highly significant for both Black and White
infants. Qualitative traits in terms of ‘’open’’ vs‘‘ closed’’ and ‘‘concordance’’ vs ‘’discordance’’
were evaluated at 12 months for both twin pairs. No significant difference in proband
concordance rates was observed in both DZ and MZ twins and the Researchers concluded that AF
19
developmental variation has a significant genetic component at 4 months, but not at 12 months.
They attributed this to the rapid brain growth which occurs between 4 to 9 months of life. These
Researchers, however, did not explore the influence of the intra-uterine environment or other
maternal conditions which may impact on foetal development in general and the developing brain in
particular 48
V. Environmental influences
In a comparative study in India, Chakrabarti50 measured the AF of 100 and 130 newborns
living in hilly and non-hilly areas in the district of Darjeeling. He found a significant difference
between the mean AF sizes of the two groups, which were 3.35 ± 1.07 cm and 3.80 ± 1.95 cm,
respectively and concluded that environmental factors such as topography and altitude may have
some influence on ossification and therefore impact on the size of the AF. It is not clear however,
whether the Researcher considered other variables before arriving at this conclusion.
Relationship between anterior fontanel size and occipito-frontal circumference
Various Researchers9,23,26,44 have documented the relationship between AF size a.nd OFC.
Tan16 found no significant association between AF and head circumference. The same finding was
documented by Duc and Largo.44This suggests that at term, increasing OFC with advancing
gestational age (GA) has no effect on the AF size. A negative correlation has instead been
documented by Duc and Largo,44 though it was not statistically significant. Adeyemo et al9 as
well as Uzoukwu26 found no correlation between OFC and AF in term neonates. Ogunye et al23 at
Ile-Ife, Nigeria found a mean OFC of 34.2 ± 3.5 cm, with a range of 27.6 – 40.0 cm. The larger
fontanel size in this series did not correlate with increase in OFC. Since the study population was
unselected, the dimensions obtained may not necessarily represent normal ranges for a healthy
population. To the best of this Researcher's knowledge, there are no previous Nigerian studies on
the relationship between AF and OFC in children up to 24 months of life.
20
Relationship between anterior fontanel size and mode of delivery
In a cohort study of 33 Brazilian neonates, Pedroso et al36 reported no significant difference
in the cranial anthropometry including AF size with respect to mode of delivery, i.e., vaginal vs.
Caesarean section. As previously noted, the small sample size in this study makes it inappropriate
to draw general conclusions. A study involving a larger sample size would be required to confirm
this finding.
Relationship between anterior fontanel size and other parameters
Different Researchers have attempted to determine the relationship between the AF size and
other anthropometric parameters such as bone age, birth weight, etc. Adeyemo and
Omotade,9Ogunye et al23 and Omotade et al14 found no significant correlation between AF size
and birth weight. Ogunye et al,23Adeyemo et al,39 and Duc and Largo44 reported no significant
relationship between AF size and bone age, head circumference or other growth parameters.
Measurement of the size of the anterior fontanel
The size of the AF can be determined clinically by palpation or radiologically using skull x-
rays and ultrasound scan.9,17,18,43 The clinical method relies on determination of the mean of the
antero-posterior and transverse dimensions15 or by calculating the area of the diamond shaped
space enclosed by its boundaries.10 The measurement is best obtained in a calm or sleeping child
and should be taken in both upright and supine positions.2,34 Different Researchers have adopted
different methods in measuring the dimensions of the AF. 10,12,15,36 These include:
I. Elsasser’s method16
This method as cited by Tan,16 appears to be the foremost method employed in the study of
the AF size. In this method, the shortest distance (“diameter”) between the two parallel sides of
the anterior fontanel is measured and the mean of the two ''opposite diameters is taken as the AF
21
size. The method of determining the size of the posterior fontanel is however, not stated.
Moreover, there is a fundamental assumption that the AF has the shape of a quadrilateral.
However, according to Davies et al,10 this is an over simplification since the bony margins of the
fontanel are rarely linear. To arrive at the shortest distance between the two parallel sides of the
AF will also require that several measurements be taken which will be cumbersome and time
consuming.
ii. Popich and Smith’s method
Popich and Smith8 in 1972, obtained the range of normal size of AF among 201 term
Caucasian newborn infants, using the average of the antero-posterior and transverse diameters
(Fig. 2). The anterior, posterior and lateral extents of the fontanel were marked on the skin surface
with a water colour pen. The measurement was by means of a non-extensible tape and recorded to
the nearest millimeter. The mean fontanel size in cm was derived from the formula: [Length (L) +
Width (W) ] / 2. Since then, other Researchers have applied the same method with varying
results.9, 14 However, a major drawback of this method is the difficulty in correctly defining the
boundaries and extent of the AF in the presence of wide sutures. This was pointed out by Tan16
and Philip.32 Popich and Smith8 assessed the newborns within one to two days of birth. Any
fontanel that was too small to be measured accurately was adjudged to be closed.. The timing of
themeasurement in the subjects examined at one day of life appears flawed in that molding is
unlikely to have resolved completely within only one day.
22
Fig. 2: Popich and Smith's8 method of measurement of the size of the anterior fontanel.
iii Fleming and Pedroso’s method36
The limits of the antero-posterior and latero-lateral distances of the anterior fontanel were
obtained by the intersection of lines tangent with the inner border of the fontanel. For this, a
translucent paper is used and marks made with a non-toxic pen, aided by palpation. The size of
the anterior fontanel is given by the formula: anterior fontanel size = (antero-posterior distance +
latero-lateral distance) /2 (Fig. 3). The reproducibility of this method in infants of African descent
with luxuriant scalp hair at birth is questionable since the translucent paper can only be easily
applied on the scalp of a baby with bald head or very scanty hair.
23
Fig. 3: Fleming and Pedroso's method36 of AF measurement.
iv. Davies’s method10
Davies et al10 studied three groups of healthy neonates and determined the size of the AF in
terms of the area enclosed by the boundaries. The neonates were grouped according to gestational
age into preterm (28-36 wks), and term infants (37-42 wks). The third group comprised of small
for gestational age infants with weights less than the 5th percentile, after correcting for sex,
maternal height and birth order. Measurements were taken after 48hrs to reduce the effect of
molding. The four apices of the AF were identified and the index finger introduced in turn into
each of the four corners. A small circular dot was marked with felt pen on the skin immediately
distal to the finger. A piece of white paper was firmly pressed over the AF so that the four dots
were transferred onto the paper (see Fig. 4). This part of the procedure was done by the same
Investigator to reduce errors. The dots on the paper were joined by straight lines to form a
quadrilateral (Fig. 5). Points A and C were joined by a straight line AC which served as a
common baseline for triangles ABC and ADC.A line (a-c) parallel to AC was then drawn through
24
D. A perpendicular was dropped from the apex B of the triangle ABC to intersect the line a-c at
X.AC and BX were then measured in millimeters and the area of the squared-figure ABCD in
millimetres (mm2) was obtained by the formula: Area of ABCD = (AC x BX) / 2.
B
A C
Fig. 5:Method of calculation of the area of anterior fontanel by Davieset al.10
a
c x
D
Area of ABCD =AC x BX
2
Fig 3 Method of calculation of the area of the anterior fontanelle (Davies et al) 12
Fig. 4: Introduction of the tip of a finger to aid delineation of the extent of the
fontanel in the method of measurement of the AF by Davies et al10
25
v. Philip’s method32
Another method of determining the size of the fontanel in terms of the area was described
by Philips32 who studied 24 babies. These were small for gestational age babies who suffered
intrauterine growth retardation. The heads of the babies were stabilized by an assistant and the AF
was covered with a piece of pliable paper (paper towel) which was well applied to the scalp. The
margins of the fontanel were then traced onto the paper. Tangential lines were drawn to the curves
delineated, and from the diameters of the diamond shape curves thus formed, the area was
calculated (Fig. 6). This method is very technical and laborious and would be difficult to apply in
a large population study.
x
a
x D b x Area = a x b
2
A B
vi. Faix’s method12
Faix12 carried out a comparative study of fontanel size in Black and White appropriately
grown newborn infants. Only subjects who met the inclusion criteria were recruited. The criteria
Fig.6: Philips's Method of calculation of the area of the
AF.32
26
included babies delivered at gestational age between 37-42 weeks as determined by maternal age
and Dubowitze score, had weight and head circumference between the 10th and 90th percentile for
gestational age and who did not have any obvious evidence of disease or malformation. Racial
assignment was determined by maternal response when asked the race of her baby. A total of 293
Black and 73 White infants were studied. All measurements were taken after 48 hours of age to
allow for the resolution of molding.To circumvent the problem of where the fontanel ended and
the suture began, the limits of the fontanel dimensions were determined by the method of Davies
et al10 (Fig. 4). The index finger of the examiner was introduced into each corner of the fontanel,
and a small dot was marked with water washable ink on the scalp immediately distal to the finger
tip (see Fig. 4). A translucent white paper was applied firmly over the AF so the dots are
transferred onto the paper.
This part of the procedure was done by the same Investigator assisted by his colleague to
minimize inter-observer error. The distance between the dots along the lateral axis, and the
longitudinal axis were measured using a fresh paper tape for each infant. On multiple occasions
the paper tapes were compared with a steel tape and no discrepancies were found. The fontanel
dimensions were recorded as length (anterio-posterio dimension) and width (transverse
dimension). The elimination of observer error by one Researcher carrying out the actual
measurement would enhance the accuracy of the results obtained but would also limit the sample
size that can be studied over a given time.
Other Researchers including Chang and Hung31 in China, Adeyemo et al,39 Omotade et
al,14Ogunye et al23 as well as Uzoukwu26 in their studies in Nigeria have applied modified
versions of one or other of the above methods with varying results, one major modification being
the age at which measurements were taken. In choosing neonates 1week to 1month, Omotade et
al14 ensured that the effects of molding did not interfere with measurements obtained. This is in
contrast to the timing of the study by Adeyemo and Omotade9 in which measurements were taken
27
at 12- 48 hrs. Although, Adeyemo and Omotade9 found AF size in Blacks that is larger than
published figures for Caucasian populations, and which agreed with other studies, it is possible
that the Researchers may have obtained an even larger AF size if the measurements had been
taken at 48-72 hrs as was the case in the method by Faix12 and Tan.16
The method used by Davies et al,10 Philips,32 and Elsasser16 was based on the assumption
that the shape of the AF is that of a regular quadrilateral. As stated earlier, this is an over
simplification as the edges of the AF are rarely linear resulting in a wide variation in the shape of
the AF.
As shown above, each of the various clinical methods of estimating AF size has its own
limitations. However, Faix12 believes that if planimetry is employed, as formulated by Scammon
and Adair27 and used by other Researchers,9,10,24,32 this method may be more accurate. However,
he still concludes that all the easily performed methods of assessment of fontanel size have their
inherent limitations and it is not clear that any single method is best.12
Age of the neonate at measurement of the anterior fontanel size
In the course of labour and delivery, the newborn’s skull is ‘molded’ and sometimes
distorted resulting in abnormal head shapes. This can present as caput succedaneum (oedema
caused by pressure over the presenting part) which usually resolves in 2 to 3 days, or the firm
skull bones can be greatly molded resulting in override of the cranial sutures.51 This presents as a
step-up feel when the skull is palpated across the suture lines, as opposed to craniosynostosis51 felt
as a ridging due to premature closure of the sutures commonly involving the sagital suture. The
guiding principle has always been the need to allow time for resolution of molding of the skull
before measuring the AF size. No literature was found on the exact day at which complete
resolution of molding occurs. Various Researchers 9,12,14,15,44 have therefore carried out the
measurement of the fontanel on different days ranging from 12 hours to 1 week.
28
Whereas Faix12 assessed the fontanel after 48 hours, Tan16 did so between 24 and 72 hours
of age. Philip32 took measurements on the 2nd or 3rd day of life and Ogunye et al23 took
measurements within 30 hours of birth while Adeyemo et al9 did so between 12-48 hours of birth.
Like most physiologic parameters in the human body, there are bound to be individual variations,
making no particular day universally acceptable. However, it is generally agreed that molding
resolves after a few days,8,10,12,14,16,51 hence following the natural history of resolution of molding,
measurements taken before the end of 24 hours may be too early.
Radiological examination of the anterior fontanel
Imaging studies using X-rays can be employed in the evaluation of the sutures and cranial
bones while ultrasonography via an open AF acting as a window into the brain can be used to
assess ventricular dilatation in hydrocephalus, andintraventricular and periventricular
haemorrhages.51,52 X rays of the skull are useful in the diagnosis of wormian bone as a cause of
delayed closure or widened fontanel.3,16 Other features visible on plain radiographs include
abnormal bridging of the sutures seen in craniosynostosis, sclerosis along suture margins, and
cortical thinning and ''beaten copper'' appearance in raised intracranial pressure.53,54,55
Clinical importance of the anterior fontanel
Although Fletcher53 believes that due to the wide intra and inter racial variations in the size
of the AF as well as variation with gestational age, routine clinical measurement of AF size has
no clinical significance, several Researchers2,9,10,15,36 however, have demonstrated evidence-based
clinical applications of the knowledge of the size and time of closure of the fontanel. Reference
values for local populations are a prerequisite for determining deviations from normal.
Abnormality in the size of the AF at any age can be due to premature or delayed closure3 which
can be congenital or acquired. Important clinical relevance of the knowledge of AF is presented
below.
29
1. Neonatal cranial ultrasonography through the fontanels
Disorders of cerebrospinal fluid accumulation can readily be detected via ultrasonography
through the AF.19,53 Serial intracranial ultra sound scans through the AF can help distinguish
between progressive and static abnormalities in ventricular volume.3,52 Neonatal cranial
ultrasonography (US) has traditionally relied on the AF as the primary acoustic window,17,18,54
which displays supratentorial anatomy and disease processes very well. However, its accuracy in
demonstrating posterior fossa abnormalities is limited, due primarily to the increased distance
between the neonatal cerebellum and the transducer.56
Two alternative neurologic US imaging techniques have been emphasized in recent
literature in the attempt to redress this problem. These are imaging through the posterior fontanel
for improved detection of small intraventricular hemorrhage17,18,56 and imaging through the
mastoid fontanel for improved visualization of the brainstem, cerebellum, and subarachnoid
cisterns.3,56,57 The proximity to the brainstem and posterior fossa afforded by the alternate
windows, i.e., the posterior and mastoid fontanels allows the use of higher frequency probes in
these areas, thereby increasing the resolution.8 However, the use of the posterior fontanel for
cranial sonography is limited to the first three months of life after which it becomes closed in
most children, whereas the AF remains patent beyond 3 months of life.
The mastoid fontanel may not fuse until 2 years of age. Imaging through the posterior
fontanel and the mastoid fontanel can significantly augment the diagnostic power of neurologic
US in detecting small intraventricular haemorrhages, subarachnoid haemorrhage, and brainstem
haemorrhage and in depicting structural abnormalities of the brainstem .54 In neonates and
infants, raised intracranial pressure leads to cortical thinning and widening of the sutures, while in
older children, raised intracranial pressure causes an im-printing of the cortical gyri on the inner
table of the cranium known as ''beaten copper appearance''30
30
Wayenberg and colleagues57 demonstrated the importance of Rotterdam tele- -transducer, a
non-invasive method of monitoring intraventricular pressure. They reported their experience in
200 neonates using this method. Statistical analysis of 25 comparative measurement between AF
pressure and invasive CSF pressure showed an excellent correlation. Hence, it was concluded that
Rotterdam tele-transducer provide accurate and reproducible values of intracranial pressure.57
2. Obstetric landmark
The anterior fontanel is an obstetrical landmark because of its distinctive diamond shape.
Palpating this fontanel on pelvic exam tells you that the forehead is just beneath your fingers.
Early in labour, it is usually difficult to feel the AF. After the cervix is nearly completely dilated,
it becomes easier to feel the fontanel in a baby with cephalic presentation. Palpation of the AF in
the midline beneath the simphysis pubis indicates that the foetal head is in the direct occipito–
anterior position which is the best position for the foetal head to traverse the birth canal.58
3. Abnormalities of anterior fontanel size and age at closure
The fontanel can become abnormal either in terms of size or age at closure.8,18,51,54-57, These
can manifest as large fontanel, delayed fontanel closure, small fontanel, early or premature
fontanel closure, bulging fontanel and sunken fontanel3. The causes of the various forms of
abnormal fontanel size and time of closure are illustrated in the following sections.
Large fontanel and delayed fontanel closure
Several medical conditions are associated with a large fontanel or delay in closure of the
fontanel. 8,15,18,59-61 A large fontanel without raised intracranial pressure may be a feature of
avariety of disorders such as skeletal abnormalities, such as achondroplasia, cleidocranial
dysostosis, osteogenesis imperfecta, chromosomal anomalies (trisomy 213), hypothyroidism,8 and
31
intrauterine malnutrition.3
The most common conditions associated with enlarged fontanels and delayed closures are
congenital hypothyroidism, achondroplasia, Down's syndrome, rickets, and increased intracranial
pressure. 2,3,18 It may also be a feature of familial macrocephaly or just a normal variant.3,5
Although these conditions have widened fontanel or delayed closure as a common feature, certain
clinical and laboratory features serve to distinguish them. The common causes of large fontanels
are shown in Table I and less common causes in Table II.
Table I: Common causes of large fontanels
Condition Characteristic features
Adapted from Kiesler J, Ricer R. The abnormal fontanel.Am Fam Phys 2003; 67: 25
Achondroplasia Widened fontanel, macrocephaly, short limb dwarfism
Congenital hypothyroidism Macrosomia, large protruding tongue, cold intolerance, mental
retardation, low T3 and T4, TSH
Down's syndrome Widened fontanel, macrocephaly, short limb dwarfism
Rickets Widened wrist, beading of the ribs, cranial bossing, low vit D
Raised intracranial pressure Bulging AF, widened cranial sutures
Normal variants Otherwise normal
Familial macrocephly Affected family members
32
Table II: Less common causes of large fontanels.
Condition Enlarged Delayed closure
Adapted from Kiesler J, Ricer R. The abnormal fontanel. Am Fam Phys 2003; 67: 2547-52
Skeletal disorders
Aperts syndrome
Osteogenesis imperfecta
VATER Association
Chromosomal abnormalities
Patau syndrome
Edward syndrome
Congenital infections
Syphilis
Rubella
Drug and toxins
Aminopterine induced
Fetal alcohol syndrome
Dysmophogenesis
Beckwith- Wiedeman syndrome
Miscelleaneous
Malnutrition
Hydranecephaly
Intra-uterine growth retardation
Hydrocephalus
33
According to Popich and Smith12 , in the absence of a raised intracranial pressure, a widened
fontanel or delayed closure is an important clue to the diagnosis of athyrotic hypothyroidism or
other conditions with retarded ossification of the calvarium. An elevated thyroid stimulating
hormone level on a newborn screening test usually detects congenital hypothyroidism, but an
abnormally large AF in conjuction with an open posterior fontanel can be early signs of the
disorder, while myxedema and growth deficiency are later signs. Mental retardation is an
inevitable result of untreated or delayed diagnosis and treatment of congenital hypothyroidism.
Routine neonatal screening tests for congenital hypothyroidism are still not available in
developing countries like Nigeria, hence a high index of suspicion aroused by such clinical
findings as widened fontanel (a component of the neonatal hypothyroid index) is vital for early
diagnosis and prompt treatment. The Presence of open posterior fontanel, a third fontanel, etc, will
help physicians in resource-poor countries in the early detection of congenital ypothyroidism.3,8,63
Infants with Down's syndrome are hypotonic with varying degrees of mental retardation and
often have affectation of other systems including congenital heart defects, flat occiput and facie,
slanting palpebral fissures and low set ears.3 Achondroplasia is an autosomal dominant disorder of
the epiphysial plate cartilage that results in dwarfism. At birth, the infant has enlarged head, low
nasal bridge, prominent forehead and shortened extremities in addition to large fontanels.3, 8,28,64
Nutritional rickets resulting from Vitamin D deficiency is now rare in the United States but
is one of the most common causes of childhood diseases in developing countries.60 Risk factors
include breast feeding without Vitamin D supplementation, dark skin and low sunlight exposure.
In rickets, there is a problem of poor mineralisation and maturation of the long bones.19 One of
the early signs of rickets is craniotabes,16,18,44,60,67 a softening of the of the outer table of the
cranial bones which buckles under pressure producing a reaction similar to the indenting and
popping back out of a ping-pong ball. Other signs of rickets in the older child include widening of
34
the ends of long bones especially at the wrist and ankles, macrocephaly with bossing of the
frontal, parietal and occipital bones , and beading of the costo-chondral junctions of the ribs.1,3,64,
Skeletal growth retardation is well documented among small for date newborns, and appears to be
responsible for a significantly larger fontanel size compared to normal term and appropriate for
date infants. Phillips32 corroborated this in a study in which 10 out of 11 of intrauterine growth
retarded newborns (birth weight < 2500 g at 38-42 wks) had widened AF measuring > 4 cm.15
The Author related the AF size to the epiphysial ossification centre and found that the intrauterine
growth retarded infants had markedly reduced epiphysial ossification which supports exposure to
chronic intrauterine growth restriction.9,31,32
Normal variants
Some infants with widened fontanels who are otherwise well with no clinical or laboratory
abnormalities have been regarded as examples of normal variants.51 Tan,16 demonstrated this with
documented AF size of 2.8 ± 0.4 cm among otherwise healthy Chinese infants which was
significantly larger than the control group.16
Small fontanel and / or premature closure of the fontanel
The AF is one of the most important sites of fusion in the cranium and thus, attracts ectopic
cutaneous tissue. It is the most common site of dermoid cysts of the cranium. 62 AF closure that
occurs as early as 3 months can be within normal range, but careful monitoring of the head
circumference in such cases is essential to exclude pathological conditions. Most pathologic
conditions that lead to early closure of the AF are associated with microcephaly.1,3, 8,15,42,60 This
may be detected using a skull x-ray but this is not done routinely. Closure of the AF is said to be
premature when it occurs before 3 months of age. The most common causes of small AF or
prematurely closed the AF are craniosynostosis and abnormal structural brain development.3
Craniosynostosis is the premature closure of the cranial sutures resulting in abnormal head shape.
Craniosynostosis can be idiopathic, or due to hyperthyroidism, hypophosphatasia, or
35
hyperparathyroidism. It is also associated with more than 50 syndromes such as Aperts,
Crouzon’s and Pfeifer’s.3,15,54,61 There is a high prevalence of clinical disorders such as seizures,
hydrocephalus, increased intracranial pressure, proptosis/papilloedema, respiratory problems,
optic atrophy and deafness (SHIPROD) in patients with craniosynostosis and microcephaly 3,4 The
risk of primary isolated craniosynostosis is 0.4 per 1000 live births.
Microcephaly is defined as head circumference less than three standard deviations below the
mean for age and sex.34,35,61 Abnormal brain growth following prenatal insults to the brain such as
maternal alcohol abuse, intrauterine hypoxia or birth asphyxia8 may result in microcephaly and
thus lead to a small fontanel or early fontanel closure. Other causes of craniosynostosis include
autosomal dominant or recessive types,dysmorphic syndromes, maternal phenylketonuria, and
universal craniosynostosis3 (see Table III). Examination at birth of the infant with
craniosynostosis might reveal a ridge over a suture or lack of movement along a suture when
alternate sides of the suture is gently pressed.3, 54, 68
TABLE III: Differential diagnosis of microcephaly
Adapted from Kiesler J, Ricer R. The abnormal fontanel.Am Fam Phys 2003; 67: 2547-52.
Chromosomal abnormalities Edward syndrome, Couson syndrome, Apert syndrome
Congenital infection Congenital syphylis, congenital rubella
Foetal alcohol syndrome
Hypoxic-ischaemic encephalopathy
Malnutrition
Structural brain defects
Normal variants
36
Overriding of the cranial sutures from the normal molding process in neonates should resolve
within the first few days of life but persists in the infant with craniosynostosis. Later physical
findings in children with primary craniosynostosis include stunted head growth, increased
intracranial pressure, proptosis, strabismus and hearing impairment. In severe cases, mental
retardation may result.54,61,70 Plain radiographs of the skull are used for initial assessment and if
craniosynostosis ispresent, a three-dimensional CT scan is obtained to detect underlying brain
abnormalitiesand to assist in planning for surgery. Prenatal insults to the developing brain such as
maternalalcohol abuse, and intra and post partum hypoxia are potential causes of microcephaly.3, 69
Bulging fontanel
In children in whom the anterior fontanel is still patent, a bulging AF is associated with raised
intracranial pressure.4, 68 Palpation may reveal a tense fontanel.3The causes of a bulging fontanel
are shown in Table IV. Meningitis and encephalitis also cause temperature instability.70 In
suspected cases, a lumbar puncture should be done after exclusion of raised intra cranial pressure
and /or decompression with manitol.71,72 Cerebrospinal fluid obtained should be sent for Gram
stain, protein, glucose, cell count and culture.
Hydrocephalus can result from an imbalance between the production and absorption of
cerebrospinal fluid.73 This condition affects 3 per 1000 live births3 and may result from congenital
malformations, intrauterine infections, intra-partum IVH especially in preterm babies as well as
from post-natal infections.3 Most cases occur before 2yrs of age when the anterior fontanel is still
patent.3 Physical signs include an abnormal rate of head growth, frontal bossing, widened cranial
sutures, and dilated scalp veins. Imaging with ultrasonography, CT or MRI shows enlarged
ventricles in the absence of brain atrophy. Associated findings include poor feeding, decreased
muscle tone, respiratory difficulties, and alterations in consciousness and seizures. Intra-
ventricular bleeds are particularly common in preterm low birth weight babies due to poorly
37
developed supporting structures in the brain. Common findings include decreased muscle tone,
seizures, falling haematocrit, vomiting, and alterations in consciousness.1,3 Dermoid tumours1,3,
59,68 of the scalp are the most frequent lesions presenting over the anterior fontanel and may also
be found over the posterior fontanel. However, they are uncommon, usually slow growing, non-
tender, benign lesions. They are twice as common in girls and can be diagnosed at birth. A CT
scan is necessary to exclude intracranial involvement.3
Adapted from Kiesler J, Ricer R. The abnormal fontanel. Am Fam Phys 2003; 67: 2547-52.
Sunken fontanel.
The primary cause of a sunken fontanel is dehydration, which can result from fluid loss in
gastroenteritis,75 persistent vomiting in hypertrophic pyloric stenosis, pharyngitis and certain
Table IV: Causes of bulging anterior fontanel
CONDITION EXAMPLES
Hydrocephalus Congenital, acquired (post-infectious).
Space occupying lesion Brain tumour, intracranial haemorrhage, brain abscess,
Intracranial Infections Bacterial meningitis, encephalitis, cerebral malaria, cysticercosis
Haematologic disorders Polycythaemia, anaemia, leukaemia.
Endocrine disorders
Hyperparathyroidism, hypoparathyroidism, hypothyroidism, Addison's
disease.
Cardiovascular disorders
Congestive cardiac failure, dural sinus thrombosis.
Miscellaneous
Hypervitaminosis A, lead poisoning, brain contusion
hypoxic–ischaemic encephalopathy.
38
inborn errors of metabolism3. Other signs include reduced peripheral perfusion, loss of skin tugor
and sunken eyes.75 An abnormal fontanel at any age can indicate a serious medical condition.
Therefore, it is important to understand the variations of normal, how to examine the fontanel and
which diagnosis to consider when an abnormality is found. Consultation with a Paediadtric
Neurologist/Neurosurgeon should be considered if a diagnosis or presence of an abnormality is
unclear.
39
JUSTIFICATION FOR THIS STUDY
The existence of racial and ethnic differences in AF size is well documented by various authors
who studied Indian, Caucasian, Israeli, Oriental, Arab and Black infants in an attempt to establish
reference values of AF sizes in their localities.9,10,14,26,35This calls for caution in applying what
may be considered normal values of AF obtained from one population to another. It also
underscores the need to obtain local reference values of normal range of AF sizes for other
populations.
The few studies done in Nigeria were among Yoruba neonates in Ile-Ife23and Ibadan,
South-West Nigeria9,14,39 and recently among Igbo neonates in Enugu in the South-East.26 The
results obtained from these studies show differences between ethnic groups in the mean size of the
AF. However, the factors responsible for these differences are yet to be determined. Also whether
such differences involve other ethnic nationalities is yet to be determined.
This Researcher did not come across any published study from the South-South
Geopolitical Zone. In addition, the previous studies were in neonates and in children not older
than 12 months of age. To the best of this Researcher's knowledge, no published Nigerian studies
are available on the size of the AF in Nigerian children up to 24 months of age.
Port Harcourt, being a cosmopolitan city is inhabited by Nigerians of diverse ethnic groups.
Therefore, a study of AF size in this heterogeneous setting can produce results that may further
highlight the occurrence of ethnic differences and which may be more representative of the
normal range of AF size in Nigerian children. Knowledge of the range of normal values of AF
size can help physicians in identifying children with abnormal AF, which could be a pointer to an
underlying disease condition.
40
It is the hope of this Researcher that the results of this study can help to achieve the
following:
1. Establish the normal range of values of AF size of Nigerian children 0-24
months old in the study population.
2. Establish the normal range of values of OFC in the study population, and
3. Provide AF size and OFC charts for use as reference standards in Nigerian children.
41
AIMS AND OBJECTIVES
General objective
To determine the variations in the size and time of closure of the anterior fontanel (AF)
from 48 hours to 24 months of age in apparently healthy Nigerian children in Port Harcourt.
Specific objectives
1. To determine anterior fontanel size at 48 hours to 7 days and at defined ages (6, 10, and
14weeks and 6, 9,12, 18 and 24 months) during the first 2 years of life.
2. To determine the OFC at 48 hours to 7 days and at defined ages (6, 10, and 14 weeks and 6, 9,
12, 18 and 24 months) during the first 2 years of life.
3. To relate AF size to the OFC at 48 hours to 7 days and at defined ages during the first 2 years
of life.
4. To determine the percentage of children in whom the AF is closed at defined ages during the
first 24 months of life.
42
SUBJECTS AND METHODS
Study design
The study was a cross sectional and analytical study carried out to determine the variations in the
size a#nd time of closure of the anterior fontanel from birth to 24 months of age in apparently
healthy Nigerian children in Port Harcourt. Clearance from the Ethics committee of the University
of Port Harcourt Teaching Hospital (Appendix I), and a written permission from Braithwaite
Memorial Specialist Hospital (Appendix II) were obtained prior to commencement of the study.
Study area
Port Harcourt, the capital city of Rivers State Nigeria, lies along the Bonny River and has a
land mass of 170km.76,77 It was founded in 1912 by the British in an area traditionally inhabited
by the Ikwere. The estimated population is 1,620,214 million according to the national population
census of 2007.76 It boasts of lush green vegetation of the rain forest and mangrove types with an
annual rainfall of 196.3 cm77and temperature range of 28-33.40C. 77 Port Harcourt City is
cosmopolitan and host to major indigenous and multinational companies in the oil and gas,
manufacturing, banking, telecommunications, construction and health sectors, employing staff
from diverse ethnic nationalities. The University of Port Harcourt Teaching Hospital (UPTH) is a
Federal Government hospital and the apex health institution in Rivers State, while Braithwaite
Memorial Specialist Hospital (BMSH) located in the heart of the City is the largest State
Government hospital and acts as a referral centre for hundreds of General Hospitals and Primary
Health Centres in the state. Besides these, there are also several Private Hospitals in Port Harcourt
Metropolis.
43
Study site
The study was carried out at the Post-Natal Ward and Special Care Baby Unit (SCBU) of
the UPTH and the Well Infants Clinics of UPTH and the BMSH, Port Harcourt. The UPTH is a
Federal Tertiary Health Institution serving Rivers State and the neighbouring states of Bayelsa,
Abia, Imo, and Akwa–Ibom. It provides specialized health care in all specialties including
Paediatrics and Obstetrics and Gynaecology. The average number of newborns in the post-natal
ward is 1700 per year. The SCBU of the Paediatrics Department is located adjacent to the Labour
Ward and has a maximum capacity for 30 in-patients. Routine newborn examination is carried out
on all babies delivered in the hospital and includes measurement of anthropometric parameters
and system examination. Preterm, very low birth weight babies, infants of diabetic mothers,
babies with macrosomia and those with birth asphyxia or congenital anomalies are immediately
transferred to the SCBU for expert care. Babies who have no indications for admission or
observation in the SCBU are transferred to the Post-Natal Ward where they are allowed a further
observation time of 48 hours. Well babies are routinely discharged after 48 hours to the Post-Natal
Clinic where they are further reviewed along with their mothers at 6 weeks of age, and if well,
they are sent to the Well Infant Clinic for immunization and further health education of the
mothers. BMSH is the apex state owned tertiary health centre and acts as a referral centre for the
primary health centres especially in the area of maternal and child health including childhood
immunizations.
Study population
All newborns of Nigerian descent admitted at the Post-Natal Ward and the SCBU and all
Nigerian children aged 6 weeks to 2 years attending the Well Infant Clinics of tertiary institutions
in Port Harcourt metropolis (within the study period) constituted the study population.
44
Study group
Neonates at 48 hours to 7 days of age at the Post-Natal Ward and the SCBU and infants of 6
weeks to 2 years of age seen at the Well Infant Clinics who met the inclusion criteria were the
subjects of this study.
Inclusion criteria
The following were included in the study.
1. Nigerian neonates delivered at 28 to 42 weeks gestational age, seen in the Post-Natal Ward
who were 48 hours to 7 days old.
2. Neurologically stable, non-critically ill neonates admitted to the Special Care Baby Unit of
UPTH delivered at a gestational age of 28 to 42 weeks who were 48 hours to 7 days old.
3. Nigerian infants who were 6 weeks to 2 years of age, who were seen at the Well Infant
Clinics of UPTH and BMSH.
4. The subjects who satisfied the above criteria and for whom informed consent (Appendix III)
was given by the parents/caregivers.
Exclusion criteria
The following were excluded from the study.
1. Critically ill babies admitted to SCBU such as those with severe birth asphyxia, severe
respiratory distress, and heart failure from any cause, congenital malformations of the central
nervous system, hydrocephalus, cephalhaematoma and caput succcaedaneum.
2. Babies born to non-Nigerian parents
3. Babies less than 48 hours or > 7 days of age.
45
4. Babies with stigmata of chromosomal anomalies.
5. Babies with stigmata of hypothyroidism.
Sample size
The desired sample size was determined in two stages. First, the sample size appropriate for
an infinite population (greater than 10000) was calculated using the formula78:
n = z2pq/d2
where n = the desired sample size when the population is more than 10000,
z = the standard variation, usually set at 1.96 (which corresponds to 95% confidence interval)
p = the proportion in the target population estimated to have a particular characteristic. If there is
no reasonable estimate, then 50% is used.
q = 1.0 –p, d = degree of accuracy desired, which for the purpose of this study was set at 0.05
Substituting the values into the formula,
n = (1.96)2 (0. 5) (0.5)
(0.05)2
= 384.
However, the population of newborns at UPTH was represented by the average deliveries
per annum in the hospital which is about 1700. While for the Well Infant Clinic, the average
attendance was 1980. These population sizes are less than 10,000.
Therefore the second formula
n= n
Where nf = minimum sample size for population less than 10,000
1+(n)
N NN
(N)
46
n= the desired sample size when the population is more than 10,000
Here n = 384
N = the estimate of the population size which is 1700 for newborns and 1980 for infants
n = 384
Substituting the estimated population sizes in the above formula,
Nf = 1+384
1700
= 384
1.227
= 313
nf2 = 384
1+384
1980
= 384
= 321
Hence the minimum sample sizes for this study were 313 newborns and 321 infants in the
other age categories. A minimum number of 313 subjects was recruited in the newborn period
from the Post-Natal Ward and the SCBU, while a minimum of 321subjects was also recruited at
each of the defined ages from 6 weeks, 10 weeks, 14 weeks,6 months,9 months, 12 months, 18
months and 24 months of age respectively.
Training of research team and standardization of method of measurement
The Investigator trained 15 assistants comprising post-internship doctors and post-NYSC
paramedics. During 4-hour practice sessions, the Research Assistants were trained on the field
techniques and measurement of AF size, weight, length, and occipito-frontal circumference of the
subjects using standard methods recommended by the World Health Organization.79 The training
47
sessions were repeated until there was mastery of the techniques as evidenced by reduction of
inter-observer error to 0.1 centimetre for measurement of anterior fontanel size, OFC and length,
and 0.1kg for weight between the Investigator and the Research Assistants. The Research
Assistants were then divided into 8 groups of 2 members each with each member taking turns to
act either as a measurer or an assistant. While one member of each team read off the
measurement, the other assisted in positioning and stabilizing the subject.
Pilot Study
A pilot study was conducted at the Braithwaite Memorial Specialist Hospital using 50
subjects to determine the feasibility of the study. In the course of the pilot study, several
mothers/care-givers expressed reservation concerning the placement of white handkerchief on the
heads of their children and the marking of same with ink. Consequently, many declined consent.
This challenge was addressed by adopting a modified version of Faix's method.12 The use of
translucent white paper unto which dots made distal to the index finger introduced into the corners
of the AF were transferred in the Faix's method12 was replaced by a pair of dividers (with the
pointed tips detached) applied to the outer border of the index and middle fingers introduced into
the corners of the AF consecutively along the transverse and longitudinal axis. The data collected
at the pilot study was not part of the analysed data.
Field work
The team went as a group to the study sites and were formerly introduced to the medical
staff at these sites. The aim and scope of the study were also explained to the staff to solicit their
cooperation. The Nursing Officer in turn informed the mothers /care-givers of our mission, and
provided a work area for the team.
Prior to taking measurement of the various parameters, the newborns were assessed to exclude
those who did not meet the inclusion criteria. The gestational age of the newborns was determined
48
using the method described by Eregie,80 and corroborated by the mother based on her last
menstrual period. Using Eregie's chart for preterm babies and the Lubchencho81 chart for term
babies, an infant is considered appropriate for gestational age if its weight is between the 10th and
90th percentile for gestational age. Measurement of the AF size and OFC in the newborns was not
done earlier than 48 hours to allow for resolution of the effects of molding.12,32 The choice of the
defined ages was made because the ages corresponded to the National Programme on
Immunization schedule and facilitated the recruitment of large number of subjects. This study
was carried out over a 10-week period. Newborns with caput succaedaneum, cephalhaematoma
were excluded because these might make it difficult to accurately delineate the limits of the AF.
Data collection
The minimum number of 313 subjects was recruited in the newborn period from the Post-Natal
Ward and the SCBU, while a minimum of 321 infants were also recruited from the Well Baby
Clinic at 6 weeks, 10 weeks, 14 weeks 6 months, 9 months, 12 months, 18 months and 24 months
of age, respectively. Data were obtained by means of a Proforma (Appendix IV) designed to elicit
demographic information of the child and mother, as well as other relevant obstetric data. The
questionnaires were separated into 9 groups and labelled according to the defined ages. These
were numbered serially until the minimum sample size for each age category was reached. The
questionnaire was self-administered where the mother /care-giver is literate. For non-literate
mothers/care-givers, it was interviewer administered by the Investigator/Assistants through a face-
to-face interview.
Tools for the field work
1. A pair of dividers which had been made blunt by detaching the traumatic pointed tips
(Appendix V). Measurements taken were read-off on a non- elastic tape stretched over a table
49
Appendix VI).
2. An electronic bassinette weighing scale for infants (Appendix VII)
3. A non- extensible tape measure for measuring occipito -frontal circumference (Appendix
VIII).
4. A wooden Infantometer (Appendix IX)
5. An electronic floor scale (SECA model 874, Secagmbh 7 co.kg, Germany)
Measurement of the size of the anterior fontanel
For the purpose of this study, the size of the AF was taken as the mean of the antero-
posterior and transverse diameters measured along the sagital and coronal sutures, respectively. A
modified version of Faix’s method12 was employed. The subject was held upright in a sitting
position by the mother/care-giver with the head supported and held firmly by the Research
Assistant while the Measurer introduced the tip of the index and the middle fingers of his/her left
hand into the two corners of the lateral dimensions of the anterior fontanel. With the pair of
dividers held in the right hand, the inner margins of the distal end of the pair of dividers were
applied firmly against the outer border of the two fingers of the left hand at the corners of the
fontanel. The pair of dividers was then placed on a tape measure firmly positioned on a table and
the distance between the inner borders of the pair of dividers was read-off on the tape (Appendix
VI). The process was repeated with the index and middle fingers placed at the corners of the
antero-posterior dimension of the AF. The size of the AF in centimetres was derived from the
relationship: (length of AF + width of AF)/2, the length and width representing the antero-
50
posterior and the latero-lateral diameters, respectively. Any fontanel too small to be measured was
adjudged closed.
Occipito-frontal circumference (Appendix VIII)
To measure the occipito-frontal circumference, the method of Student2 was employed. A non-
elastic tape was placed circumferentially over the glabella, the bi-parietal and occipital
prominence (see Appendix VIII). This was read off in centimetres and recorded to the nearest
millimetre. The tension of the tape was such that the hair was firmly pressed against the head.
Three measurements were done for each child. The highest was taken as the OFC. All three
measurements in a given subject were taken by the same Investigator/ Research Assistant.
Length
Supine length was measured using a wooden infantometer/floorboard (Appendix IX). The
Research Assistant firmly held the crown of the head of the subjects against the head board, and
positioned the head in such a way that the right upper margin of the external auditory meatus and
the lower margin of the orbit of the eye were perpendicular. The Measurer then stretched the body
and the legs of the subject and brought the sliding footboard into firm contact with the soles of the
feet. The measurements were read to the nearest millimetre.
Weight
To measure the weight of the subjects, a SECA electronic bassinette scale (Appendix VI) was
used for newborns and infants not more than 12 months old. The infants were weighed naked.
Infants older than 12 months old were weighed using an electronic floor scale (SECA model 874,
Secagmbh 7 co.kg, Germany) with the subject bare footed and naked, standing still at the centre
of the scale. The accuracy of the scales used were ascertained by placing known weights on the
scales and making adjustments where necessary before commencement of weighing of subjects
each day. The scale reading was ascertained to be at zero before each reading was taken.
51
Measurements were read to the nearest 0.1kg when the pointer had stopped oscillating, with the
measurer looking directly at the scale in the vertical plane.
All measured parameters as well as gender, gestational age (for newborns), birth weight,
length and OFC were recorded on a proforma (Appendix IV)
Socio-economic status classification
Using the socio-economic classification described by Oyedeji82 each subject was assigned a socio
-economic class based on the occupation and educational attainment of both the mother and the
father. A socio-economic index score of 1 to 5 was assigned for each parameter. The sum of the 4
scores was divided by 4 to obtain the socio- economic class of the child.
Ethical Consideration
Ethical clearance was obtained from the Ethics Committee of the University of Port
Harcourt Teaching Hospital (Appendix I). A written permission (Appendix II) was also obtained
from BMSH. Detailed explanation of the study procedure and extent of involvement of each
subject was given to the mothers/caregivers. Written informed consent (Appendix III) was
obtained from the parent(s) or care-giver(s) of each child before recruitment into the study. The
children observed to have abnormal fontanel size such as those with a closed fontanel at 2 to 7
days and those with an open fontanel at 24 months were referred to the Paediatric Neurology
Clinic for follow -up.
Analysis of data
Data was analyzed using the Statistical Package for Social Sciences (SPSS) Version
15.0.83The mean, standard deviation and range of each continuous variable and other derived
indices including the 5th, 10th, 25th, 50th 75th, and 95th percentiles were computed and presented as
graphs, and tables in simple proportions. The differences in means were compared using Student’s
52
t test while Chi–square test was used to compare proportions and rates. Pearson’s Correlation
Coefficient was used to determine the relationship between AF and OFC at 48 hours to 7 days and
at defined ages. Analysis of Variance (ANOVA) was used to ascertain the significance of the
differences in the means of AF and OFC at various ages. Multiple comparisons of the differences
in mean AF between age groups was carried out using Dunnette’s83 Test. Statistical significance
at 95% confidence interval was set at p- value < 0.05.
53
RESULTS
SOCIO-DEMOGRAPHIC CHARACTERISTICS OF THE STUDY GROUP
Table V shows the distribution of the subjects. Two thousand eight hundred and ninety nine
subjects were recruited into the study. One newborn and three infants were excluded on the basis
of incomplete data due to mother's uncertainty of the child's age leaving a total study population
of 2,895. Of these, 1391 (47.5%) were males and 1504 (52.5%) females, giving a male to female
ratio of 1:1.1. There was no statistically significant difference between the proportion of males
and females in any of the recruitment ages.
Table VI shows the distribution of the newborns by gender and gestational age. Of the 313
newborns, 250 (79.9%) were term while 63 (20.1%) were preterm. The ratio of males to females
among the term and preterm newborns was 0.96:1 and 0.7:1, respectively. There was no
significant difference in gender ratio among the term newborns (p > 0.05), whereas among the
preterms the number of females (37) was significantly higher than that of males (26), (p < 0.05).
Of the 250 term infants, 146 (58.4%) were delivered at 37-39 weeks of gestation and 104 (41.6%)
at 40-42 weeks gestation. Among the 63 preterm newborns, 47 (74.6%) and 16 (25.4%) were
delivered at 33 - 36 weeks and 28 - 32 weeks of gestation, respectively.
Table VII shows the distribution of the study subjects by ethnic group. The Igbo was the
largest ethnic group followed by the Ikwere/Etche group and the Hausa/Fulani the least.
Table VIII shows the distribution of the study subjects according to social class. One
thousand seven hundred and sixty five (61%) were of the higher social classes (I and II), whereas
269 (9.3%) were of the lower social classes
54
Table V: Distribution of the subjects by age and gender
Age Male
No. (%)
Female
No. (%)
Total
No. (%)
2-7 days 153 (11.00)
160 (10.6) 313 (10.8)
6 wks. 165 (11.9)
157 (10.4) 322 (11.1)
10 wks. 167 (12.0) 158 (10.5) 325 (11.2)
14 wks. 155 (11.1)
168 (11.2) 323 (11.2)
6 mo. 159 (11.4)
166 (11.1) 325 (11.2)
9 mo. 156 (11.2)
165 (11.0) 321 (11.1)
12 mo. 164 (11.8)
157 (10.4) 321 (11.1)
18 mo. 139 (10.0)
182 (12.1) 321 (11.1)
24 mo. 133 (9.6) 191 (12.7) 324 (11.2)
Total 1391 (100.0) 1504 (100.0) 2895 (100)
χ2 = 12.34, df = 8, p = 0.137
55
Table VI. Distribution of newborns by gestational age and gender
Gestational age
Male
No. (%)
Female
No. (%)
Total
No. (%)
Preterm 28-36 wks
26 (17.0)
37 (23.1)
63 (20.1)
Term 37-42 wks
127 (83.0)
123 (76.9)
250 (79.9)
Total 153 (100.0) 160 (100.0)
313 (100)
χ2 = 1.83, df = 1, p = 0.176
56
Table VII. Distribution of the subjects by ethnic group
*Efik, Ekpeye, Ibani, Idoma, Ndoni and others
.
Ethnic Group No. (%)
Igbo 1040 (35.9)
Ikwerre/Etche 505 (17,4)
Yoruba 217 (7.5)
Urhobo/Itsekiri 215 (7.4)
Ijaw/Kalabari/Okirika 195 (6.7)
Anang/Ibibio/Oron 180 (6.2)
Ogoni 119 (4.1)
Bini/Esan 112 (3.9)
Hausa/Fulani/Tiv/Langtan, 31 (1.1)
Others* 284 (9.8)
Total 2895 (100)
57
Table VIII. Distribution of subjects by social class
So Social class No (%)
Class I
686 (23.7%)
Class II
1079 (37.3%)
Class III
861 (29.7%)
Class IV
227 (7.8%)
Class V
42 (1.5%)
Total
2895 (100%)
58
VARIATION IN ANTERIOR FONTANEL SIZE
Table IX shows the variation of mean anterior fontanel size by age and sex. There was a
highly statistically significant trend of decreasing AF size with age in both males and females
with all the p-values < 0.001 for ANOVA. There was no significant difference in mean AF size
between males and females except at 10 weeks (p = 0.029), 6 months (p = 0.04), 12 months (p =
0.008) and 24 months (0.002). The correlation between AF size and age in both males and
females is illustrated graphically in the scatterplot on page 63
Table X shows the mean AF size of term and preterm newborns. There were no significant
differences between males and females or between term and preterm newborns, all p values being
> 0.05.
The results of multiple comparisons of differences in mean AF size between the different
age groups is shown in Table XI. There was a statistically significant difference (p < 0.001)
between the mean AF size of newborns and those of infants aged 6 months, 12 months, 18 months
and 24 months. There was also a statistically significant difference (p < 0.001) between the mean
AF size at 6 months and at 12, 18 and 24 months, and between those at 12 and 18 months. There
was no significant difference (p > 0.05) between the mean AF size at 18 months and 24 months.
Figure 7 is a scatterplot illustrating the variation in AF sizes with increasing post-natal age.
There was a strong negative correlation between AF size and post-natal age in both males (r = -
0.747; p < 0.001) and females (r = -0.782; p < 0.001). The mean AF size in males was
significantly higher than that in the females, with more females having a closed anterior fontanel
with advancing post-natal age beyond 9 months of age (p < 0.05).
59
Table IX. Variation in mean AF sizes by postnatal age and gender
Post Post natal age
Anterior fontanel size (cm)
Male Female All Subjects t-test p-value
No. Mean (SD) No. Mean (SD) No. Mean (SD)
2-7 days 153 4.5 (1.6) 160 4.5 (1.8) 313 4.5 (1.7) -0.06 0.096
6 wks 165 4.3 (1.5) 158 4.2 (1.3) 323 4.3 (1.4) 1.18 0.239
10 wks 167 4.1 (1.3) 158 3.8 (1.6) 325 3.9 (1.5) 2.19 0.029
14 wks 154 3.6 (1.2) 168 3.5 (1.2) 322 3.6 (2.2) 0.43 0.667
6 mo 158 3.3 (1.2) 167 2.9 ( 1.4) 325 3.1 (1.3) 2.21 0.028
9 mo 156 2.3 (1.3) 165 2.6 (1.3) 321 2.5 (1.2) -1.45 0.148
12 mo 164 2.0 (1.6) 157 1.6 (1.0) 321 1.8 (1.3) 2.67 0.008
18 mo 140 0.3 (0.7) 181 0.1 (0.4) 321 0.2 (0.6) 1.89 0.060
24 mo 134 0.4 (1.0) 190 0.1 (0.4) 324 0.2 (0.7) 3.08 0.002
All Subjects 1391 2.9 (2.2) 1504 2.5 (2.0) 2895 2.7 (2.1) 4.39 0.001
*F 226.93 16.07 537.37
p–value < 0.001 < 0.001 < 0.001
*F statistic for ANOVA
60
Table X. Variation of mean AF sizes of newborns by gestational age and gender.
Gestational
age
Anterior fontanel sizes(cm)
Male Female All Subjects t-test p-value
No. Mean (SD) No. Mean (SD) No Mean (SD)
Preterm
28-32 7 4.4 (1.8) 9 3.8 (2.0) 16 4.0 (1.9) 0.62 0.545
33-36 19 4.5 (1.7) 28 4.5 (2.2) 47 4.5 (2.0) 0.05 0.957
Term
37-39
68
4.6 (1.7)
78
4.6 (1.8)
146 4.6 (1.8)
0.07
0.942
40-42
59
4.4 (1.4)
45
4.5 (1.4)
104 4.4 (1.4)
-0.31
0.757
All
Subjects
153
4.5 (1.6)
160
4.5 (1.8)
313 4.5 (1.7)
0.05
0.958
*F 0.18 0.56 0.61
P-value 0.910 0.642 0.608
*F statistic for ANOVA,
61
Table XI. Dunnett’s multiple comparisons of differences in mean AF size between different age groups
Age
Category
(J) Age
Category
Mean
Difference
(I-J)
95% Confidence Interval
p-value
Lower
limit
Upper
limit
2 - 7 days
6 months 1.38 1.06 1.71 < 0.001
12 months 2.72 2.39 3.06 < 0.001
18 months 4.30 4.03 4.58 < 0.001
24 months 4.28 3.99 4.56 < 0.001
6 months
12 months 1.34 1.06 1.63 < 0.001
18 months 2.92 2.70 3.13 < 0.001
24 months 2.89 2.67 3.12 < 0.001
12 months 18 months 1.58 1.36 1.8 < 0.001
24 months 1.55 1.32 1.78 < 0.001
18 months 24 months -0.025 -0.16 0.11 > 0.05
Mean difference and 95% confidence interval are given in cm
62
Figure 7: Scatter plot of variations of AF size by postnatal age and gender
p-value< 0.05
Females R2 Linear = 0.612
Males R2 Linear =0.558
63
The variation in percentile of anterior fontanel size with age is illustrated in Table XII. The
5th, 50th, and 95th percentiles of the AF size at birth were 1.3, 4.7 and 6.7 cm. At 24 months, the
values were 0.0, 0.0 and 1.4 cm respectively. The variations in mean AF size with increasing post-
natal age was statistically significant (ANOVA = 537.37 p < 0.001). The variation in 5th, 50th, and
90th percentiles with age is illustrated in Fig. 8.
Table XIII shows the relationship between AF size and social class at the different ages
studied. Among the newborns, the AF was largest in the subjects belonging to social class V and
least in those of class II. The subjects belonging to social class I had the largest AF size at 2-7
days, 10 weeks, and at 14 weeks of life while the AF size was least in those belonging to class V
at 9, 18 and 24 months of age. The difference in the mean AF sizes between the various social
classes was highly statistically significant in all the age categories except at 2-7 days, 14 weeks, 6
months and 18 months. A graphical illustration of the differences in mean AF size between the
subjects belonging to low, middle and high socio-economic classes is shown in Figure 9.
Table XIV shows the variation in mean AF size among newborns by ethnic group. Those
from the Ogoni ethnic group had the largest AF (6.4 ± 1.5 cm) while the Hausa/Fulani had the
smallest (3.0 ± 3.5 cm). There was a highly statistically significant difference between the mean
AF size of different ethnic groups (p < 0.001).
64
TABLE XII. Mean, range and percentiles of AF in the study group
Age
Days
Weeks
Months
AF Characteristics 2-7
(n = 313)
6
(n = 323)
10
(n = 325)
14
(n = 322) 6
(n = 325)
9
(n = 321)
12
(n = 321)
18
(n = 321)
24
(n = 324)
Mean size ± SD 4.5
±1.7
4.2
±1.4
3.9
±1.5
3.7
±2.2
3.1
±1.0
2.5
±1.3
1.8
±1.3
0.2
±0.6
0.0
±0.7
Minimum size 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
Maximum size 7.9 6.6 6.9 3.6 6.6 5.0 4.7 3.3 0.0
5th centile 1.3 1.8 1.4 1.5 0.5 0.9 0.0 0.0 0.0
10th centile 2.0 2.2 2.0 1.9 1.5 1.0 0.0 0.0 0.0
25thcentile 3.5 3.5 2.9 2.8 2.1 1.3 0.5 0.0 00.0
50th centile 4.7 4.5 4.1 3.6 3.3 2.4 1.9 0.0 0.0
75th centile 5.8 5.2 5.0 4.3 4.1 3.6 2.8 0.0 0.0
90th centile 6.40 5.9 5.9 5.1 4.7 4.3 3.3 0.7 1.0
95th centile 6.7 6.2 6.2 5.9 5.0 4.7 4.7 1.2 1.4
F statistic for ANOVA = 537.37, p < 0.001 for the variation of mean AF size with postnatal age.
Figures given in cm.
65
Figure 8: Variation in the 5th, 50th and 95th percentile of AF size with postnatal age.
0
1
2
3
4
5
6
7
8
2-7 days 6 wks 10 wks 14 wks 6 months 9 months 12 months 18 months 24 months
5th Percentile
50th Percentile
95th Percentile
2-7 6 10 14 6 9 12 18 24
Days weeks months
Postnatal age
66
Table XIII. Relationship between mean anterior fontanel size, social class and age
* F statistic for ANOVA
Social
class
Mean (SD) AF size (cm)
Days Weeks Months *F p-value
2 - 7 6 10 14 6 9 12 18 24
I 4.6 (1.4) 4.5 (1.6) 4.7 (1.5) 3.8 (1.4) 3.3 (1.2) 2.6 (1.5) 0.9 ( 0.8) 0.1 (0.4) 0.0 223.24 < 0.001
II 4.3 (1.8) 4.1 (1.4) 4.0 (1.3) 3.5 (1.2) 3.1 ( 1.4) 2.3 (1.2) 1.5 (1.1) 0.2 ( 0.6) 0.2 (0.5) 207.32 < 0.001
III 4.6 (1.7) 4.0 (1.2) 3.0 (1.4) 3.5 (1.1) 3.1 (1.2) 2.4 (1.2) 2.4 (1.5) 0.2 (0.7) 0.6 (1.3) 104.84 < 0.001
IV 4.4 (1.8) 4.1 (1.2) 4.1 (0.6) 3.7 (1.4) 3.3 (1.3) 3.2 (1.4) 0.3 (0.8) 0.3 (0.4) 0.0 73.73 < 0.001
V 5.2 (0.0) 6.2 (0.4) 4.1 (0.0) 2.3 (0.0) 2.2 ( 0.7) 0.0 2.6 ( 0.7) 0.0 0.0 67.17 < 0.001
*F 0.84 4.68 21.67 1.08 1.13 5.80 21.48 1.38 10.91
p- value 0.501 0.001 < 0.001 0.389 0.342 0.001 < 0.001 0.241
< 0.001
67
Figure 9: Variation of mean AF size by social class
0.000
1.000
2.000
3.000
4.000
5.000
6.000
Mea
n A
F si
ze in
cm
Upper Class Middle Class Lower Class
2-7 6 10 14 6 9 12 18 24
days weeks months
Postnatal age
68
Table XIV. Variation of mean AF size with ethnic group among the newborns.
Ethnic group No. Mean ± SD AF size
Ogoni 36 6.4 (1.5)
Bini/Esan 9 5.5 (1.4)
Anang/Ibibio/Oron Ibo 20 5.2 (1.6)
Ikwere / Etche 50 5.1 (1.7)
Yoruba 22 5.1 (1.5)
Urhobo/Itsekiri 19 4.2 (1.3)
Igbo 120 3.9 (1.7)
Ijaw/Kalabari/Okirika 22 3.7 (1.6)
Hausa/Fulani/Tiv/Lantan 5 3.0 (3.5)
Others 31 4.9 (1.2)
Total 313
F statistic for ANOVA = 3.59, p < 0.001
AF size given in cm
69
VARIATIONS IN THE MEAN OCCIPITO-FRONTAL CIRCUMFERENCE
Table XV shows the variation of the mean of occipito-frontal circumference with postnatal age in
males and females. The mean OFC of male infants was significantly higher than that of their female
counterparts at 6 weeks, and at 6, 9, 12 and 18 months with p-values of < 0.05 at 6 weeks and 6
months and p-values of between 0.005 to < 0.001 at 9, 12 and 24 months. There was a positive
correlation between increased postnatal age and OFC, with the mean OFC increasing from 35.8 ± 2.8
cm in newborns to 48.0 ± 2.3 cm at 24 months (r = 0.617, p < 0.001). This is illustrated in the scatterplot
in Fig.10. Those from the Ogoni ethnic group had the largest AF (6.4 ± 1.5 cm) while the Hausa/Fulani
had the smallest (3.0 ± 3.5 cm). There was a highly statistically significant difference between the mean
AF size of different ethnic groups (p < 0.001).
Table XVI shows the variation of mean of OFC of newborns by gestational age and gender.
There was a moderate positive correlation (r = 0.346) between OFC and increasing gestational
age, which was, however, not statistically significant (p = 0.004). The difference in the mean OFC
between males and females was also not statistically significant in any gestational age group
except at 37 to 39 weeks (p < 0.05).
The results of Dunnett's multiple comparisons of differences in mean OFC between
different age groups is shown in Table XVII. Highly statistically significant differences (p <
0.001) were observed all through except at 18 versus 24 months (p < 0.05).
Table XVIII shows the mean, range and percentile values of the OFC in the study subjects.
The 5,th 50th and 95th percentiles of OFC of 32.2 cm, 35.2 cm and 38.8 cm, respectively at birth
increased to 45.3 cm, 48.0 cm and 50.6 cm, respectively, at 24 months of age. The variation in 5th,
50th and 95th percentile values with postnatal age is illustrated graphically in Figure 11.
70
Table XV. Variation of mean occipito-frontal circumference by age and gender
Age
Mean SD OFC (cm)
Male Female All Subjects t-test p-value
No. Mean (SD) No. Mean (SD) No. Mean (SD)
2-7 days 153 35.9 (2.5) 160 35.6 (2.8) 313 35.8 (2.7) 0.47 0.335
6 wks 165 36.9 (1.8) 158 36.7 (2.3) 323 36.8 (2.1) 2.02 0.045
10 wks 167 39.7 (2.9) 158 39.1 (2.4) 325 39.4 (2.7) 0.88 0.381
14 wks 154 43.2 (2.3) 168 41.9 (2.8) 322 42.6 (2.6) 1.31 0.190
6 mo 158 44.5 (3.4) 167 46.1 (1.6) 325 45.3 (2.5) 2.00 0.046
9 mo 156 47.1 (1.3) 165 45.2 ( 3.2) 321 42.6 (2.3) 5.27 < 0.001
12 mo 164 47.9 (1.5) 157 47.2 (2.5) 321 47.6 (2.0) 7.15 < 0.001
18 mo 140 47.5 (1.3) 181 47.1 (2.1) 321 47.3 (1.7) 2.85 0.005
24 mo 134 49.0 (2.9) 190 48.0 (1.8) 324 48.0 (2.3) -0.64 0.526
All Subjects 1391 42.7 (4.8) 1504 42.4 ( 2.4 2895 42.6 (4.9)
1.70
0.090
*F 728.70 507.22 7461.14
p-value < 0.001 < 0.001 < 0.001
*F statistic for ANOVA,
mo = months, SD = Standard deviation, OFC = Occipito-frontal circumference, wks = Weeks
71
Figure 10: Scatterplot of variations of OFC by postnatal age in males and females
Males = R2 Linear 0.566
Females: = R2 Linear = 0.653
72
Table XVI. Variation of mean occipito-frontal circumference of newborns by gestational age and gender.
Gestational
Age
Mean (SD) OFC
t-test p-value
Male
No. Mean (SD)
Female
No. Mean (SD)
All Subjects
No. Mean (SD)
28-32 7 33.8 (4.5) 9 33.6 (3.65) 16 33.6 (3.9) 0.10 0.921
33-36 19 35.9 ( 2.0) 28 36.6 ( 3.7) 47 36.2 (3.1) 0.67 0.506
37-39 68 36.4 (2.9) 78 355 ( 2.4) 146 35.9 (2.6) 2.01 0.046
40-42 59 35.6 (1.5) 45 35.7 ( 2.5) 104 35. 9(2.9) 0.09 0.932
Over all
mean (SD) 153 35.9 (2.5) 160 35.6 (2.8) 313 35.8 (2.7)
1.70
0.090
0.090
*F 1.28 0.51 4.45
p-value 0.204 0.611 0.004
*F statistic for ANOVA
cm = centimetres; SD = Standard Deviation; OFC = Occipito-frontal circumference (OFC) given in cm
73
Table XVII. Dunnett’s multiple comparisons of differences in mean OFC between different age groups
Age category (J) Age
category
Mean
difference
(I-J)
95% Confidence Interval
p-value Lower
limit
Upper
limit
2 - 7 days
6 months -7.46 -8.02 -6.91 < 0.001
12 months -10.41 -10.98 -9.84 < 0.001
18 months -11.72 -12.25 -11.27 < 0.001
24 months -12.21 -12.73 -11.68 < 0.001
6 months 12 months -2.95 -3.50 -2.4 < 0.001
18 months -4.26 -4.76 -3.76 < 0.001
24 months -4.74 -5.24 -4.22 < 0.001
12 months 18 months -1.31 -1.83 -0.79 < 0.001
24 months -1.79 -2.31 -1.27 < 0.001
18 months 24 months -0.48 -0.95 -0.02 < 0.05
Mean difference and 95% confidence interval are given in cm
74
Table XVIII. Mean, range and percentiles of OFC in the study subjects
OFC
Characteristics Days Weeks Months
2-7 6 10 14 6 9 12 18 24
(n = 313) (n = 323) ( n = 325) (n = 322) (n = 325) (n = 321 (n = 321) (n = 321) (n = 324)
Mean (SD) OFC 35.8 (2.7) 37.5 (2.1) 139.9 (2.6) 40.23 (2.6) 42.2 (2.5) 45.3 (2.3) 46.2 (2.) 47.4 (1.7) 47.8 (2.3)
Min. OFC 24.4 28.8 33 31.6 31.6 32.0 32.0 32.0 34.0
Max .OFC 47.2 47.6 44.1 48.5 38.8 52.0 50.1 53.2 51.1
5th centile
32.4 35.0 34.15 35.5 39.86 41.2 40.3 45.8 45.3
10th centile 33.1 35.2 36.3 37.0 40.1 43 44.8 46.04 46.1
25th centile 34.2 36.2 38.0 39.1 41.8 44.5 45 46.8 47.0
50th centile 35.8 37.3 39.5 40.5 43.1 45.9 46.7 47.6 48.o
75th centile 37.0 38.4 40.7 42.0 45.0 47.0 47.8 48.3 49.1
90th centile 38.2 39.5 41.5 43.0 46.7 47.2 48.3 49.1 50.3
95th centile 38.8 40.5 42.0 44.46 47.1 48.1 48.79 49.99 50.6
ANOVA = 46.14, p < 0.001 for the variation of mean OFC with postnatal age.
Min. = Minimum,
Max. = Maximum
75
0
10
20
30
40
50
60
2-7 days 6 wks 10 wks 14 wks 6 months 9 months 12 months 18 months 24 months
5th Percentile
50th Percentile
95th Percentile
Age
days weeks months
Fig. 11: Variation of the 5th, 50th and 95th percentiles of OFC with postnatal age.
2-7 6 10 14 6 9 12 18 24
76
COMPARISON OF THE TRENDS OF AF SIZE AND OFC WITH POST NATAL AGE
Table XIX and Figure 12 illustrate the relationship between AF size and OFC with
postnatal age. The mean AF size decreased significantly with age (ANOVA = 784.72, p <
0.001), whereas the mean OFC increased significantly with age (ANOVA = 1368.68, p <
0.001). There was a highly statistically significant correlation (r = 0.648, p = 0 .001) between
AF size and OFC with postnatal age, given by the formula y = 14 - 0.265x, where y = AF and
x = OFC. The mean AF size decreased even as the mean OFC increased with age (Figure 12).
Table XX shows the proportion of the subjects in each age group with a closed anterior
fontanel. The number with a closed AF was 76 (23.7%) at 12 months, 273 (85.1%) at 18
months and 288 (88.9%) at 24 months. Nine (2.9 %) of the 313 newborns had a closed AF.
The proportion of subjects with a closed AF at different age categories is illustrated in Figure
13.
77
Table XIX. Correlation between the AF size and OFC and age
AF = Anterior fontanel; mo = months; OFC = Occipito-frontal circumference
Age 2-7days
(n= 313)
6 mo
(n = 325)
12 mo
(n = 321)
18 mo
(n = 321)
24 mo
(n = 324)
ANOVA p-value
Mean (SD)
AF in cm
4.5 (2.0)
3.1 (1.3)
1.8 (1.3)
0.2 (0.6)
0.2 (0.7)
784.72
< 0.001
Mean (SD)
OFC in cm
35.8 (2.6)
43. 2 (2.5)
46.2 (2.6)
47.5 (2.1)
48.0 (2.2)
1368.68
< 0.001
78
Figure 12. Scatterplot of the correlation between anterior fontanel size and occipito-frontal
circumference with postnatal age.
y = -0.265x + 13.95R² = 0.419
-1
0
1
2
3
4
5
6
7
8
9
20 25 30 35 40 45 50 55
Ave
rage
An
teri
or
Fon
tan
el S
ize
(cm
)
OFCMean Occipito-Frontal Circumference (cm)
Circumference
79
Table XX. Relationship between postnatal age and closure of anterior fontanel
+
Postnatal
age
Males* Females** All subjects*** a χ2 P-value
No. n (%)
with closed AF
No. n (%)
with closed AF
No. n (%; 95% CI) with
closed AF
2-7 days 153
2 (1.3) 160 7 (4.4) 313 9 (2.9; 0.66-2.64) 2.64 0.104
6 weeks 165
5 (3.0) 158 1 (0.0) 323
6 (1.9; 0.66 - 2.64) 2.55 0.111
10 weeks 167
0 (0) 158 0 (0) 325
0 - -
14 weeks 154
4 (2.6) 168 0 (0) 322
4 (1.2; 0.19 - 1.60) 4.42 0.036
6 months 158
2 (1.3) 167 5 (3) 325 7 (2.2; 0.46 - 2.25) 1.15 0.283
9 months 156
0 (0) 165 4 (2.4) 325
4 (1.2; 0.19 -1.64) 3.86 0.050
12 months 164
40 (24.4) 157 36 (22.9) 321 76 (23.7; 18.26 - 28.2) 0.10 0.758
18 months 140
118 (84.3) 181 155 (85.6) 321
273 (85.1; 74.38 - 89.56 ) 0.11 0.737
24 months 133 113 (85.0) 191 175 (91.6) 324 288 (88.9; 78.8- 94.08) 3.52 0.061
aχ2 = proportion with closed fontanel in males vs females in different age categories
*χ2 (Variation of proportion with closed AF with age in males) = 903.64, p < 0.001.
**χ2 (Variation of proportion with closed AF with age in females) = 1081.11, p < 0.001.
***χ2 (Variation of proportion with closed AF with age in all subjects) = 1991.47, p < 0.001.
CI = Confidence interval
80
Figure 13: Variation in percentage closure of anterior fontanel with postnatal age.
2.9 1.90
1.2 2,2 1.2
23.7
85.1
88.9
0
5
10
15
20
25
30
35
40
45
50
per
cen
tage
wit
h c
lose
d A
F
100
90
80
70
60
50
40
30
20
10
2.-7 6 10 14 6 9 12 18 24
days weeks months
Postnatal age
81
DISCUSSION
The mean size of the anterior fontanel in this study decreased significantly with age. This
trend has been documented by previous Authors,4,7,23,30,42 among Caucasian as well as Black
infants.
The mean AF size of 4.5 ±1.7 cm in newborns in this study is higher than that in previous
reports from Nigeria.9,14,23,26,39 However, there was marked variation between the sizes reported
from previous studies. Thus, while Adeyemo et al39reported a mean AF size of 4.0 ± 1.0 cm,
Ogunye, et al23 and Uzoukwu26 reported lower values of 3.3 ± 2.0 cm and 2.78 ± 0.82 cm,
respectively. One possible reason for the difference between the mean AF size in the present
study and those in previous studies could be the timing of the measurements, which was within
12 to 24 hours after birth in the series by Adeyemo et al,39 at 30 hours in that by Ogunye et al23
and at 24-48 hours in that by Uzoukwu.26 Although the exact duration of the effects of molding
on the AF is uncertain, it is likely that measurements taken after 48 hours and up to 7 days post-
natal as was done in the present study could reduce the effects of molding. The implication of
this is that the higher values of AF sizes obtained in this study may be more valid than that from
studies in which measurements were taken at less than 48 hours of age. It is thus possible that, if
the timing of measurements in the previous Nigerian studies had been as in the present study, the
results may have been similar.
Another factor that may be responsible for the differences in mean AF size could be the
method of measurement. In the method used by Popich and Smith,8which was adopted by some
of the other Researchers,9,14,39it is not stated as to how the limits of the AF were delineated. The
method of Faix,12 adopted by Uzoukwu,26 would appear to be less suitable for our newborns with
luxuriant scalp hair, as it can predispose to falsely higher values.10,26 Accurate delineation of the
limits of the AF is paramount to getting a reliable measurement.10 Since the method of
delineation of the AF by Faix12 and Uzoukwu,26 are fraught with inherent errors, and the method
82
by Popich and Smith, which was used by the other Researchers did not state how the AF
dimension was delineated, these may account for the lower values in AF sizes in their reports.
The use of a pair of dividers aided by palpation as was employed in the present study
would appear more appropriate as the limits of the AF can easily be delineated despite the
luxuriant scalp hair in Nigerian newborns. On the other hand, the fact that the pointed tips of the
pair of dividers were detached could be contributory to the higher AF values obtained in this
study. In addition, the subjects in this study were from diverse ethnic groups while the earlier
Nigerian Authors9,14,23,26 surveyed homogenous groups. The factors responsible for the variation
in AF size between different ethnic groups demonstrated in this study are not clear and require
further evaluation.
The mean size of the AF in this study was also higher than the figures obtained from
Caucasian8,12and Oriental populations.16,26This is in accord with previous studies that have
documented racial differences in the size of the anterior fontanel.12,14,16,23,24 It is also possible that
these differences may be related to the different methods employed in the measurement of the
AF size. However, although the extent to which the use of different methodologies influence the
size of the AF remains to be determined, a generally larger AF size has been documented in
Black neonates compared to their White counterparts. This is thought to be due to delayed
osseous maturation akin to that seen in small-for-dates neonates and those with skeletal
dysmorphogenesis.8,23
The relationship between AF size and gestational age as found in this study is similar to
that
documented previously both locally9,26,39 and internationally.10,44,45 However, that no significant
difference in the mean AF size was observed between preterm and term babies in the present
study contrasts with the findings of other Nigerian Authors.14,26The reason for this is not clear
but may be related to the small sample size of the babies born at 28-32 weeks GA compared to
those born at 33-36 weeks GA in the present study.
83
There was no statistically significant gender difference in the mean size of the AF among
the younger infants in the present study. This is in accord with previous studies, both locally
14,24,26,39 and internationally.6,8,45 However at 24 months of age, the mean AF size was
significantly lower in females. This is in contrast with the findings by Tan16 who reported no
gender difference with respect to the size and time of closure of the AF among Chinese children.
In the present study, there was a positive correlation between OFC and gestational age up
to 36 weeks. It thus appears that beyond 37 weeks of intra-uterine life, AF is not significantly
dependent on gestational age and supports the fact that a gestational age of at least 37 weeks is
appropriate as a cut off for considering a baby term. Since the OFC and AF are indices of brain
growth, the correlation may be reflective of the differences in the rate of brain growth in term
and preterm babies. While Malas and Sulak41 reported a gradual but progressive increase in AF
size with head circumference in the third trimester, several other Authors including Adeyemo
and Omotade,9 Tan16 and Ogunye, et al23 and Duc and Largo44 found no association between the
AF size and OFC in term and preterm newborns.
The mean OFC at birth in the present study (35.8 ± 2.7 cm) is significantly higher than the
34.2 ± 3.5 cm reported by Ogunye23et al in Ile-Ife, and the 34.5 ± 3.2 cm reported by Lubchenco
et al81 for United States Caucasians. It is uncertain whether the larger OFC observed in this study
at 0 to 12 months compared to those from previous studies23,81 is a reflection of the previously
reported cyclical trend of a larger OFC in succeeding generations as documented by Ounsted et
al.84
Previous Nigerian scholars had reported on occipito-frontal circumference in newborns and
children up to 12 months.23,26,39, This Author did not come across published Nigerian studies on
OFC in children up to 24 months of age. This is perhaps, therefore, the first of such, and the
values reported in this study may be the only currently available standard for OFC in Nigerian
children from 12 to 24 months of age.
84
The values of OFC obtained in this study were significantly lower at 18 months and 24
months than that reported for Oxford children by Ounsted et al.84It is possible that the lower
occipito-frontal circumferences obtained in this study beyond 12 months compared to that of
Caucasian figures may be due to the high prevalence of malnutrition in our environment.85 This
buttresses the need for local reference standards which should be updated as necessary with each
succeeding generation.
A strong negative correlation between AF and OFC was observed in relation to increasing
post-natal age in the present study. This is in concert with the findings of Chang and
Hung,31Popich and Smith,8 and Tan.16 The growth in OFC of the subjects observed from the
newborn period to 24 months of age is also consistent with the findings in previous reports.16,46
The results of this study show that the anterior fontanel can be derived from the OFC using
the formula: AF = 14 - 0.265 (OFC). The measurement of the AF involves some technicalities,
and requires an assistant to ensure a reliable measurement. Therefore, the availability of a simple
formula can be helpful especially in a busy clinic setting. However, further studies may be
required to validate the application of this formula before it can be recommended for use in
clinical practice.
About 3% of the newborns in this study had a closed anterior fontanel. This is in contrast
to the findings of Ogunye23 and Uzoukwu,26 who reported an open AF in all the newborns
studied. Also this Researcher did not come across any published study that had reported closure
of the AF fontanel in apparently healthy newborns. However, there was no obvious abnormality
among the newborns in the present study and care had been taken to exclude all newborns with
obvious neurological, skeletal, endocrine and chromosomal disorders. Therefore, the reason(s)
for the finding of a closed AF in some of the newborns in the present study is/are not clear. Also,
whether this is a normal variation in Nigerian children remains to be determined.
85
There was a steady increase in the proportion of subjects with a closed anterior fontanel
with increasing post-natal age beyond 9 months of age. The percentage with a closed AF at 24
months (88.9%) in the present study is similar to the 91% reported from Indian by Mattur et al37.
In the series by Omotade et al,14 11% of 6 months infants and 53% of 12 months olds had a
closed anterior fontanel. The percentage of infants with a closed anterior fontanel in the present
study at 6months of age is lower (2.2%) while that at 12 months (23.7%) is higher. Apart from
the differences in methodology noted earlier, the larger sample size in the present study may also
have played a role by increasing the chance of picking ''abnormal'' findings.
About 11% of the subjects in the present study still had an open AF at 24 months. This is
higher than the 4% reported by Duc and Largo44 from Zurich. It is possible that the relatively
high prevalence of nutritional rickets in our environment could explain the high percentage of
subjects with an open AF at 24 months in this study.85
Males had a significantly larger mean AF size At 24 months of age, whereas more females
had a closed AF at same age. The difference in percentage closure between males and females
was, however, not statistically significant. These findings contrast with those of Acheson and
Eirly47 who demonstrated earlier closure of the AF in European boys. However, Acheson and
Eirlys study47 was conducted during a period of male preference with better nutrition in male
children which could explain their findings. Further studies are required to confirm the findings
in this study and to seek explanations for the male-female difference.
Over 60% of the subjects in this study were of the higher social classes while only about
10 % were in the lower classes. However, this may not be a reflection of a higher standard of
living in the inhabitants of Port Harcourt metropolis but rather a reflection of the relatively high
educational status of majority of the mothers/care-givers which has a positive influence on their
health-seeking behaviour.
86
There was a significant relationship between anterior fontanel size and social class. This is
similar to the finding of Acheson and Eirlys47 who noted a larger AF size in the lower social
classes and an earlier closure in the higher social-economic classes. Further studies are required
to establish the relationship between nutritional status and AF size in Nigerian children.
The cosmopolitan nature of Port Harcourt City, the study area, is reflected in the diverse
ethnic nationalities of the inhabitants. The relatively higher number of Igbo infants in this study
may not be unrelated to the migrant nature of the Igbo who are found in every nook and cranny
of the country and beyond. This is in addition to the fact that the Igbo speaking states of Imo and
Abia are neighbouring states to Rivers State and are among the catchment area for UPTH.76
AF size varied widely among the different ethnic groups but among the newborns, the
largest AF size was observed among the Ogoni, while the Hausa/Fulan/Tiv/Lantang had the least
AF size. The mean AF size in Igbo neonates in this study is similar to that reported by
Uzoukwu26 among Igbo neonates in Enugu. This is perhaps a reflection of their common racial
origin. Similarly, the mean AF size for the Yoruba newborns in this study is within the range
reported by Omotade et al.14This, therefore, suggests that inheritance exacts a stronger influence
on AF size than environmental factors. The significant difference in the mean AF sizes between
the various ethnic groups studied is suggestive of inter-ethnic variations in the size of the AF.
The factors responsible for these variations, other than inheritance, remain to be determined.
87
CONCLUSION
1. The size of the anterior fontanel in Nigerian children in the cosmopolitan city of Port Harcourt
decreases progressively with post-natal age even as the occipito-frontal circumference
increases.
2. The relationship between occipito-frontal circumference and anterior fontanel size is given by
the formula AF = 14 - 0.265 (OFC).
3. Three percent (95% confidence interval = 0.66, 2.64) of Nigerian newborns in Port Harcourt
have a closed AF but the anterior fontanel is still open in 11% (95% confidence interval =
78.80, 94.04) of the subjects by 24 months of age.
4. Socio-economic status and ethnicity are important determinants of the size of the anterior
fontanel.
88
RECOMMENDATIONS
1. The values of the 5th, 50th and 95th percentile for anterior fontanel size and occipito-frontal
circumference at various ages obtained in this study are recommended for use as reference
standards in Nigerian infants in Port Harcourt.
2. Mothers/care-givers should be educated at every opportunity especially during ante-natal
visits, and at the Post-Natal and Well-Infant Clinics that the size of the anterior fontanel varies
at different ages, and thereby discourage wrong practices that may predispose them to other
illnesses.
89
LIMITATIONS OF THE STUDY
1. A major limitation of this study was the time constraint posed by the necessity to conclude the
research within the time frame of the senior residency program. For this reason, a cross
sectional study was carried out, and therefore percentage closure was obtained rather than the
actual age at closure of the anterior fontanel which would require a longitudinal study.
2. The method adopted for the estimation of the AF size may be a factor in the finding of a closed
fontanel in 3% of newborns. Estimation of the anterior fontanel size by means of trans-fontanel
ultrasound scan would have given a more accurate result in terms of delineation of the limits of
the AF.17
90
LINES OF FUTURE STUDIES
Further studies are recommended in the following areas:
i. Follow-up of apparently well newborns with closed AF to determine the effect on development
ii. The relationship between nutritional status and AF size, and time of closure
iii. The causes of premature closure and delayed closure of the anterior fontanel in the study
population.
iv. Validation of the formula for the computation of the size of the anterior fontanel from the
occipito-frontal circumference.
91
REFERENCES
1. Still BJ, Kliegman RM. The newborn infant. In: Behrman RE, Kliegman RM, Jenson HB,
(eds).Nelson Textbook of Pediatrics, 16th ed. Philadelphia. WB Saunders Co., 2000; 454-60.
2. Haslam RHA. Neurological evaluation. In: Behrman RE, Kliegman RM, Jenson HB, (eds).
Nelson Textbook of Pediatrics,16th ed. Philadelphia. WB Saunders Co., 2000; 1793- 1866.
3. Kiesler J, Ricer R. The abnormal fontanel. Am Fam Phys 2003; 67: 2547-52
4. Soames R. Skeletal System: In Grays H. Williams PL Bannister LH (eds). The Anatomical
Basis of Medicine and Surgery, 38thed. New York: Churchill Livingstone, 1995; 425-36.
5. The Anterior fontanel, Http://www.ncbi.nlm.gov/sites/enterez; Brandt I, Hodes DT, Reimnitz
P. Assessed 28th August 2009.
6. Finnegan M, Heisler R, Miller M, (eds). Webster’s II New Riverside University
Dictionary. Boston. Riverside Publishing Co., 1984: 596.
7. Joseph J. The locomotor system. In: Hamilton WJ, (ed). Textbook of Human Anatomy. 2nded
London, Macmillan Publishers, 1987; 19-200.
8. Popich GA, Smith DW. Fontanels: range of normal size. J Pediatr 1972; 80: 749-52.
9. Adeyemo AA, Omotade OO. Variation in fontanel size with gestational age. Early Hum Dev
1999; 54: 207-14.
10. Davies DP, Ansari BM, Cooke TJH. Anterior fontanel size in the neonate. Arch Dis Child
1975; 50: 81-3.
11. Mir NA, Weislaw R. Anterior fontanel size in Arab children. Standards for appropriately grown full
term neonates. Ann Trop Paediatr 1998; 8: 184–6.
92
12. Faix R. G. Fontanel size in black and white term newborn infants. J Pediatr 1982; 100: 304-6.
13. Sinclair D. Growth. In: Hamilton WJ. (ed) Textbook of Human Anatomy.2nd Ed. London Macmilian
Publishers, 1987; 713-27.
14. Omotade OO, Kayode CM, Adeyemo AA. Anterior fontanel size in Nigerian children. Ann
Trop Paediatr 1995; 15: 89-91.
15. Smith DW, Popich G. Large fontanels in congenital hypothyroidism: a potential clue toward
earlier recognition. J Pediatr 1972; 80: 753-6.
16. Tan, KL. Wide sutures and large fontanels in the newborn. Am J Dis Child 1976; 130: 386-
90.
17. Donald N Di Salvo. A new view of the neonatal brain: Clinical utility of supplemental
neurologic US imaging windows. Radiographics.2001; 21: 943-55.
18. Origins of neonatal intensive care in the UK. In Christie DA, Tansey EM, Ed, Welcome
witnesses to twentieth century medicine. London, United Kingdom: Wellcome Trust; 2001;
9: 1-7.
19. Fernell E, Hagberg G, Hargberg B. Infantile hydrocephalus epidemiology: an indicator of
enhanced survival. Arch Dis Child 1994; 70: 123-8.
20. Feingold M, Bossert WH. Normal values for selected physical parameters: An aid to syndrome
delineation. Birth Defects 1974; 10: 1-6.
21. Laestadius BA, Aese MD, Smith DW. Normal inner canthil and outer orbital dimensions. J
Pediatr 1969; 74: 465-8.
22. Pryor HB. Objective measurement of inter-pupillary distance. Pediatrics 1969; 44: 937-9.
93
23. Ogunye O, Ikeji MO, Adeodu O. Craniofacial dimensions in the African neonate. Niger J
Paediatr 1982; 9: 21-5.
24. Omotade OO. Facial measurements in children (towards syndrome delineation). I Med Genet
1990; 27: 358-62.
25. Ibe BC, Nwosu KC. Outer canthal and inner canthal distances in Nigerian newborn babies,
Paper presented at the 24th annual conference of the Paediatric Association of Nigerian,
Enugu. January 1993.
26. Uzoukwu C. Assessment of anterior fontanelle sizes of Igbo newborns in Enugu Nigeria
Dissertation submitted to West Afr Col of Phy Oct 2009.
27. Scammon RE, Adair FL.The geometric relationships of the frontal fontanel in infancy. Anna Rec
1930; 46: 349-55.
28. Tomashek KM, Nesby S, Scanlon KS. Nutritional rickets in Georgia. Pediatrics 2001; 107: 45-8
29. Sadler TW, Langman J. Skeletal system, In: Langman’s Medical Embryology. 8th ed. Philadelphia.
Lippincott. William & Wilkins, 2004; 171-5.
30. Robinson DC, Hall R, Munro DS. Graves disease: an unusual complication - raised intracranial
Pressure due to premature fussion of the skull sutures. Arch Dis Child 1969; 44: 252-55.
31. Chang BF, Hung KL. Measurement of anterior fontanel in Chinese children. Acta Paediatr
Sinica 1990; 31: 307-12.
32. Philips AGS. Fontanel size and epiphyseal ossification in neonate s with intrauterine growth
retardation. J Pediatr 1974; 84: 2047.
33. 33.Anatomy of the newborn skull. Pediatric health information.webmaster@chw.org<accessed
21st Sept. 2009>.
94
34. Amiel-Tison C, Gosselin J, Infant-Rivard C. Head growth and cranial assessment and neurological
examination in infancy. Dev Med Child Neurol 2002; 44: 643-8.
35. Srugo I, Berger A. Anterior fontanel size in healthy Isreali newborn infants. Isr J Med
Sci.1987; 23: 1137-9.
36. Pedroso IS, Rotta N, Quintal A, Giordani G. Evolution of anterior fontanelle size in normal
infants in the first year of life. J Child Neurol 2008; 23: 1419-3.
37. Mattur S, Kunna R, Mathur GP, Singh VK, Gupta V, Tripathin V. Anterior fontanel size. Ind J
Paediatr 1994; 3: 161-4.
38. Belden CJ. The skull base and the calvaria: adult and paediatric. Neuro-imaging.Paediatr Clin N
Am 1998; 8: 1-20.
39. Adeyemo AA, Olowu JA, Omotade OO. Fontanel size in term neonates in Ibadan, Nigeria.
W Afr J Med 1991; 18: 55-9.
40. Katiyar GP, Sen S Aggarwal KN. Anterior fontanel during infancy. Ind J Paediatr 1975; 12:
1253-6.
41. Verma KC, Maggotra MC. Effect of different milk on head growth and size of anterior
fontanel at various age periods. Ind J Paediatr1978; 16: 131-6.
42. Indira-Bai K, Subrahmanyam MVG, Subba-RaoKV. Fontanels: Range of normal size. Ind J
Paediatr 1973; 10: 667-70.
43. Walia BNS, Bhalia AK. Norms of anterior fontanel size of Punjabi children. Ind J Paeditr
1985; 22: 303-6.
44. Duc G, Largo RH. Anterior fontanel” size and closure in term and preterm infants. Pediatrics 1986;
78: 904-48.
95
45. Uzura M, Furuya Y, Mashi K, Sekimo H. Persistence of open fontanel in a 4 year old girl.
Child’s Nerv Syst 2005; 2: 83-5.
46. Malas MA, Sulak O. Measurements of anterior fontanel during the foetal period, J Obstet &
Gynaecol. 2002; 20: 601-5.
47. Acheson RM, Eirlys J. Some observations on the closure of anterior fontanelle. Arch Dis Child
1954; 29: 196-8.
48. Poswillo D. Causal mechanisms of craniofacial deformity, Br Med Bull 1975; 32: 101-5.
49. Melnick M, Myrinthopoulus NC, Christain JC. Estimates of genetic variance for anterior fontanel
development in NCPP twin population. Acta Genet Med Gemellol. 1980; 29: 151-5
50. Chakrabarti k Anterior fontanel size n hilly and non-hilly newborns n and around the district of
Dejeerling. Ind J Paediatr 1989; 26: 41-4.
51. Rennie JM, Gandy GM. Exaamination of the newborn. In: Rennie JM, Roberton NRC, (eds).
Textbook of Neonatology 3rd ed. Edingburg: ChurchHill Living stone. 1999: 269-77.
52. Machado HR, Martelli N, Assirati JA Jr. Colli BO. Infantile hydrocephalus: Brain sonography as
an effective tool for diagnosis and follow up. Child Nerv Syst 1991; 7: 205-20.
53. Fletcher MA. Physical Assessment and classification In: Neonatology, Pathophysiology and
management of the Newborn 5thed. Philadelphia Lippincott.William &Wilkins, 1999; 301-32.
54. Prober CG. Acute bacterial meningitis beyond the neonatal period. In: Behrman RE, Kliegman
RM, Jenson HB (eds). Nelson textbook of Pediatrics.18thed, Philadelphia, Saunders, 2000; 751-61.
55. Liptac GS, Paediatric approach to craniosynostosis. Paediatr Rev 1998; 19: 352-8.
56. Luciania G. Use of posterior fontanel in the ultrasonographic diagnosis of intraventricular
/periventricular haemorrhage. J Pediatr 2008; 84: 21-6.
96
57. Wayenberg JL, Vermeylen D, Raftopoulos C, Detemmerman D, Muller MF, Pardou A.
Mornitoring of fontanel pressure in neonates and infants.Evaluation of a new measuring technique,
determination of normal values and clinical usefulness.Rev Med Brux 1993; 14: 209-15.
58. Fetal position/http/www.brooksidepress.org/products/military_OBGYN/.Accessed 16th May
2009.
59. Rothman SM, Lee BC. What bulges under a bulging fontanel. Arch Pediatr Adolesc Med1998;
152: 100-1.
60. Akpede GO, Ekanem EE, Thacher TD. Nutritional and non-nutritional rickets in the tropics. In:
Azubuike JC, Nkanginieme KEO (eds). Paediatrics and child health in a tropical region. Owerri:
African Educational Services, 1999; 456-73.
61. Sundine MJ. Abnormal head shapes in children: classification and syndromes. J Keny Med
Assoc 1999; 97-107.
62. Sundine MJ. Clinical findings and treatment of children with abnormal head shapes. J Keny
Med Assoc 1999; 248-54.
63. Taeusch HW, Sniderman S. Initial evaluation history and physical and examination of the
newborn. In: Taeussch HW, Ballard RA (eds). Avery's Disease of the Newborn 7th ed.
Philadelphia, WB Sounders, 1998; 334-53.
64. Azubuike JC. Endocrine and metabolic disorders. In: Azubuike JC, Nkanginieme KEO (eds).
Paediatrics and child health in a tropical region. Owerri: African Educational Services, 1999; 456-73.
65. Larry AG, Rickets In: Behrman RE, Kliegman RM, Jenson HB. (eds). Nelson Textbook of
Pediatrics. 18th ed. Philadelphia, Saunders, 2007; 1696-1714.
66. Usher RH. Clinical and therapeutic aspects of fetal malnutrition.Pediatr Clin N Am 1970; 17: 169-
74.
97
67. Joseph RM, In: NEONATOLOLGY, Pathophysiology and Management of the Newborn. 5th ed.
Philadelphia Lippincott. William &Wilkins,1999; 564-85
68. Humberto B Del Aquino.Congenital dermoid inclusion cyst over the anterior fontanel.
Macmillan Publishers,Arq.Neuro-Psiquiatr 1987; 61: 713-27.doi:10.1590/S0004-
282X2003000300022. Accessed 25th July, 2009.
69. Izuora GI Inflammatory diseases of the central nervous system. In: Azubuike JC, Nkanginieme
KEO (eds). Paediatrics and child health in a tropical region. Owerri, African Educational Services,
999; 362-81.
70. Dale J, Muurer PK. Abnormal head In: ZiaiM (eds). Bedside Paediatric Daignostic Evaluation of
the Child. Boston. Little Brown, 1983; 97-107.
71. Robert Haslam, Neurologic evaluation In: Behrman RE, Kliegman RM, Jenson HB (eds). Nelson
textbook of Pediatrics. 18thed, Philadelphia, Saunders, 2007; 2440-45.
72. Peter Gal, Michael Reed, General medications. In: Behrman RE, Kliegman RM, Jenson HB
(eds). Nelson textbook of Pediatrics. 18thed, Philadelphia, Saunders, 2007; 2266-83.
73. Charles G Prober, Central nervous system infections.In: Behrman RE, Kliegman RM, Jenson HB
(eds). Nelson textbook of Pediatrics. 18thed, Philadelphia, Saunders, 2007; 2513-23.
74. Stephen LK, Michael VJ Congenital anormalies of the central nervous system. In: Behrman RE,
Kliegman RM, Jenson HB (eds). Nelson textbook of Pediatrics.18thed, Philadelphia, Saunders,
2007; 2452-5.
75. Akinbami FO. Diarrhoeal diseases in childhood In: Azubuike JC, Nkanginieme KEO (eds).
Paediatrics and child health in a tropical region. Owerri: African Educational Services, 1999; 283-
7.
98
76. PH population. http://www.en.wikipedia.org/wi.Accessed 16th May, 2009.
77. worldweather. http://www.org/075/c00325.htmPH. Accessed 16th May, 2009.
78. Araoye, M.O. Sample size determination. In: Research Methodology with Statistics for Health
and Social Sciences. Nathadox publishers, Ilorin: 2004; 115–22
79. Child growth. http://www.who.int//physicalstatus /publications/index.htm. Accessed 30th May
2012
80. Eregie CO. A new method for maturity determination in newborn infants. J Trop Pediatr
2000; 46: 140-4.
81. Lubchenco L.O, Hansman C, Dressler M, Byd E. Intrauterine growth as estimated form live born
birth weight data at 24-42 weeks of gestation. Pediatrics 1963; 32: 793-800.
82. Oyedeji GA. Socioeconomic and cultural background of hospitalized children in Ilesa. Nig J
Paediatr 1985; 12: 11–17.
83. Statistics for Dummies. Deborah Rumsey- “Google books” www.books.google.com. 2009-
08-19. Accessed 22-08-2012.
84. Ounsted M, Moar VA, Scott A. Head circumference charts updated. Arch Dis Child.1985;
60: 936-9.
85. T.O Ulasi, Joy Ebenebe. Nutritional Disorders in Childhood In: Azubuike JC, Nkanginieme
KEO (eds). Paediatrics and child health in a tropical region. Owerri: African Educational Services,
1999; 250-67.