ORIGINAL PAPER
Endoscopic endonasal approaches to anterior skull base
defects in pediatric patients
Davide Locatelli & Federico Rampa & Ilaria Acchiardi &
Maurizio Bignami & Andrea Pistochini &
Paolo Castelnuovo
Received: 22 December 2005# Springer-Verlag 2006
Abstract
Introduction We studied 12 pediatric patients with congen-
ital or acquired anterior skull base defects. All subjects
underwent surgery owing to progressive symptoms. The
endoscopic endonasal approach is a new method in the
treatment of this pathology in children.
Materials and methods Twelve children had surgery to
correct anterior skull base defects: seven patients with a
spontaneous anterior basal meningoencephalocele and five
with posttraumatic cerebrospinal fluid (CSF) leakage. The
defects were repaired using the endoscopic endonasal
approach, which combined with the fluorescein diagnostic
test, detects the exact location of the skull base defect.
Different closure techniques were used to obtain a
permanent graft, depending on the type, location, and size
of the defect. An intraoperative fluorescein test confirmed
the absence of CSF leakage after surgery.
Results The follow-up period ranged from 3 to 72 months.
Symptoms resolved in all patients after surgery and none of
them experienced complications or recurrence of CSF
leakage. Postoperative magnetic resonance scans showed
that the defect had successfully been repaired in all patients.
Discussion The surgical treatment of skull base defects in
children reduces life-threatening risks, which include
infections, CSF leaks, and enlargement or trauma of the
sac. The endoscopic technique minimizes surgical scars and
has little impact on brain tissue. The endoscopic endonasal
approach to the anterior skull base helps to preserve the
physiology of the nose and sinuses and reduces the impact
on the still developing splanchnocranium in pediatric
patients. It ensures a definitive repair of the defect and
requires a very short inpatient period.
Keywords Endoscopy . Endonasal surgery .
Meningocele . Rhinorrea . Skull base .
Congenital defect . Cerebrospinal fluid leaks . Fistula
Introduction
Anterior skull base defects in children can be congenital
(meningoencephaloceles) or posttraumatic (skull base frac-
tures). Anterior basal meningoencephaloceles are rare,
representing 10–20% of all craniospinal dysraphisms [1]
with an incidence of 1:5,000 live births, as reported by
Suwanwela and Suwanwela [2]. Nasoethmoidal encephalo-
celes protrude through a defect between the nasal bone and
nasal cartilage; the most common symptoms are progres-
sive nasal obstruction with mouth breathing, snoring, and
nasal discharge due to the projection of the herniated mass
into the nasopharynx [1]. Transsphenoidal encephaloceles
are associated with more serious abnormalities of the
midline of the brain and sometimes involve vital structures
[3, 4].
Posttraumatic cerebrospinal fluid (CSF) leaks in chil-
dren, with an incidence of 0.2–0.3% of all head traumas in
Childs Nerv Syst
DOI 10.1007/s00381-006-0114-7
D. Locatelli (*) : F. Rampa : I. Acchiardi
Department of Neurosurgery, IRCCS Policlinico S. Matteo,
University of Pavia,
27100 Pavia, Italy
e-mail: [email protected]
M. Bignami : P. Castelnuovo
Department of Otolaryngology, Ospedale di Circolo,
University of Insubria,
Varese, Italy
A. Pistochini
Department of Otolaryngology,
University of Sassari,
Sassari, Italy
childhood, are less common than in adults. The greater
plasticity of the bone and the incomplete development of
the paranasal sinuses mean that the traumatic event can be
absorbed. Posttraumatic cerebrospinal fluid leaks occasion-
ally cause intermittent rhinorrhea, and the only symptom
may be recurrent episodes of meningitis.
Early surgical repair is necessary to avoid the risk of
infection and progressive breathing impairment in congen-
ital meningoencephaloceles.
We report our results on 12 children with anterior skull
base defects, seven with congenital meningoencephaloceles
and five with posttraumatic lesions and CSF leaks. All
operations were performed using an endonasal endoscopic
technique.
Materials and methods
We operated on 135 patients with anterior skull base defects
between May 1995 and May 2004. Endonasal endoscopic
repair was carried out in 121 cases, and a combined
intracranial–extracranial approach was used in 14. The
present study included 12 children, six males and six females,
whose ages ranged from 1 to 18 years (mean age 8 years).
Seven children, three males and four females, had a
congenital meningoencephalocele, which was clinically
revealed by nasal obstruction (four cases) or recurrent
meningitis (three cases). The malformation involved the
cribriform plate in five cases, the ethmoid and the sphenoid
sinus in one case, respectively (Table 1). Five children,
three males and two females, sustained head injury and
CSF leakage after being involved in a car accident (three
cases), after being kicked by a horse (one case), and after
heading a ball (one case). The lesion was confined to the
ethmoid in one patient but was multiple in the remaining
cases: two children had lesions in the ethmoid and
cribriform plate, one in the ethmoid and the sphenoid
sinus, and one in the ethmoid and the posterior wall of the
frontal sinus. Rhinorrhea was the initial symptom in these
children and was associated with headache in one case
(Table 2). Two of these patients had previously been treated
at other institutions: a 12-year-old girl for a meningo-
encephalocele in the sphenoid sinus and a 12-year-old boy
for posttraumatic CSF leakage.
Diagnostic tests included laboratory tests, endoscopic
evaluation, computed tomography (CT) and magnetic
resonance (MR) imaging studies.
Beta-2-transferrin detection in fluid samples collected
from the nose was used as a diagnostic test when active
rhinorrhea was present [5].
We performed endoscopic endonasal evaluation to
visualize CSF leaks or monolateral nasal obstruction, as
well as to rule out any other nasal anatomical variations
(Fig. 1).
Spiral CT, with a bone and high-definition multiplanar
reconstruction (MPR) algorithm, was performed with the
Table 1 Symptoms presented by patients with congenital skull base defects
Case Age Sex Onset sign Location of the skull
defect
Side MEP Previous attempts to
repair the CSF leak
FU
1 1 F Nasal obstruction Cribriform plate Left Yes No 19
2 1 M Nasal obstruction Cribriform plate Left Yes No 12
3 3 M Nasal obstruction Cribriform plate Right Yes No 38
4 4 F Nasal obstruction Cribriform plate Right Yes No 69
5 8 M Recurrent meningitis (four episodes) Cribriform plate Left Yes No 12
6 14 F Recurrent meningitis (three episodes) Ethmoid Right Yes No 30
7 12 F Recurrent meningitis (four episodes) Sphenoid, pterygoid Left Yes Yes 13
FU Follow-up (months), MEP meningoencephalocele
Table 2 Symptoms presented by patients with posttraumatic anterior skull base defects
Case Age Sex Etiology Onset sign and
symptom
Location of the skull
defect
Side Previous attempts
to repair the CSF leak
FU
1 4 F Horse kick Rhinorrhea Ethmoid Left No 63
2 11 M Header Rhinorrhea Ethmoid, cribriform plate Left No 71
3 12 M Car accident Rhinorrhea Ethmoid, sphenoid sinus Right Yes 29
4 18 M Car accident Rhinorrhea Ethmoid, cribriform plate Right No 81
5 17 F Car accident Rhinorrhea with headache Ethmoid, posterior wall
of frontal sinus
Left No 14
FU Follow-up (months)
Childs Nerv Syst
patient in a supine position. This provided detailed studies
in the axial, coronal, and sagittal planes, which localized
the bony defect. CT cisternography was not performed.
MRI with 3-mm slices was carried out with T1- and T2-
weighted sequences and in the fluid attenuated inversion
recovery sequence when necessary. Contrast enhancement
was used to better define the content of the sac in the event
of masses projecting into the nasal cavity.
All posttraumatic patients had a preoperative fluorescein
test to confirm CSF leakage and, when possible, to pinpoint
the lesion, in accordance with Stammberger [6]; we also
took CSF samples for laboratory tests.
All patients underwent endoscopic endonasal repair of
the skull base defect.
The surgical procedure was performed under general
anesthesia and blood pressure was controlled. After
inducing anesthesia, the intrathecal contrast was injected,
following Stammberger’s guidelines, before graft place-
ment in the definitive surgical position [6, 7].
All surgery was performed with the patient lying on his
back with his head slightly extended and turned to the right,
facing the surgeon; head clamps were not used. The child’s
face was cleansed and covered with a sterile cloth with a hole
for the nose. Tampons soaked with topical anesthetic and
vasoconstrictor drugs were inserted into both nostrils using
bayonet forceps [8, 9]. The tampons were removed after 5 to
10 min, and local anesthetic drugs were then injected
submucosally, under endoscopic vision, to facilitate the
detachment of the nasal mucosa from cartilage or bone surface.
The direct paraseptal endonasal approach was performed
in five patients with a meningoencephalocele in the
cribriform plate. In these cases, the middle turbinate had
been pushed aside by the protruding mass and was thus
conserved. A specific blade was used to separate the
mucous membranes of the septal and lateral walls as far as
the subperiosteal plane to reach the pedicle of the lesion. The
extruding dural wall was dissected from the bone and
mucoperichondrium, fully exposing the defect in the bone;
Table 3 Surgical repair of congenital anterior skull base defects
Case Location MEP Previous attempts to
repair the CSF leak
Graft Graft material FU
1 Cribriform
plate
Yes No Combined Dural substitute + cartilage (underlay) and mucoperichondrium
(overlay)
19
2 Cribriform
plate
Yes No Composite Septal mucoperiostium + cartilage 12
3 Cribriform
plate
Yes No Combined Dural substitute + cartilage + septal mucoperiostium 38
4 Cribriform
plate
Yes No Free
simple
Abdominal fat 69
5 Cribriform
plate
Yes No Combined Middle conca bone + dural substitute + mucosa of conche bullosa 12
6 Ethmoid Yes No Combined Dural substitute + middle conca bone + dural substitute (underlay)
and middle turbinate mucoperiostium (overlay)
30
7 Sphenoid,
pterygoid
No Yes Combined Dural substitute + cartilage (underlay) and mucoperichondrium
(overlay)
13
FU Follow-up (month)
Fig. 1 a T1 coronal MR
study showing a congenital
meningoencephalocele in
the right nasal fossa, which
dislocates the nasal
structures. b Endoscopic
appearance
Childs Nerv Syst
the meningeal layer was then opened and the contents of the
sac, if judged to be still functional, were replaced inside the
skull base using an appropriate spatula. We used a combined
graft to repair the defect in four cases and a free simple graft
with abdominal fat in one patient (Table 3).
An ethmoidectomy was carried out when the defect was
localized in the ethmoid or if the defect involved both the
cribriform plate and the ethmoid. The mucoperichondrium
surrounding the defect was detached, and bipolar forceps
were used to reinsert the meningeal protrusion. A combined
graft was used in these cases (Table 4).
The transethmoidal–pterygoidal–sphenoidal approach
was used in one case to correct a meningoencephalocele
of the lateral sphenoid sinus. The ethmoidectomy was
combined with the excision of the middle turbinate and a
wide antrostomy to identify the posterior wall of the
mascellar sinus and the pterygoid that was finally drilled
out to expose the lateral wall of the sphenoid sinus. An
intraoperative fluorescein test confirmed the absence of
CSF leakage in all cases. The grafts were then fixed into
position with fibrin glue and held in place by hemostatic
fibrillary sponges or Vaseline gauzes [10, 11]. Nasal
packing was left in place for about 2 days.
All patients underwent postoperative endoscopic evalu-
ation and MR imaging 1 month after surgery. The MR test
was performed under sedation (depending on the patient’s
age), during which endoscopic endonasal evaluation was
also performed.
Results
Seven children had congenital defects of the anterior skull
base. On endoscopic endonasal evaluation, the four
children with monolateral nasal obstruction had a smooth,
whitish-gray mass protruding into the nasal cavity. Of the
three patients with recurrent meningitis, one had a small
pulsating mass in the anterior portion of the olfactory
groove, another did not present abnormalities, while the
patient who had previously undergone surgery at another
hospital had a pulsation in the pterygoid area, which
synchronized with his heart beat.
The five children with posttraumatic skull base lesions
presented with monolateral rhinorrhea. On endoscopic endo-
nasal evaluation, four patients were found to have a normal
anatomy, while one patient had a meningoencephalocele.
Beta 2 transferrin was tested in all patients with active
rhinorrhea; all tested cases were positive.
Complete imaging studies were performed in all cases:
CT delineated bony structures while MR identified the
content of the sac and checked for the presence of other
brain abnormalities [12].
An intraoperative fluorescein test allowed us to pinpoint
the leak in 11 of the 12 children [9]: endoscopic endonasal
exploration was performed on all our patients. The direct
paraseptal endonasal approach was used in five patients with
a meningoencephalocele in the cribriform plate. An ethmoi-
dectomy was carried out in one patient with a small
ethmoidal meningoencephalocele and in five patients with
posttraumatic CSF leaks (the defect was confined to the
ethmoid in the 4-year-old girl, while the remaining four
cases presented multiple defect sites). The transethmoidal–
pterygoidal–sphenoidal approach was used in one patient
with a meningoencephalocele of the lateral sphenoid sinus.
Intraoperative fluorescein tests confirmed that the defect had
successfully been repaired in all cases with no CSF leakage.
None of our patients developed complications or
required repeat surgery.
Table 4 Surgical repair of posttraumatic anterior skull base defects
Case Location of the skull
defect
Side Graft Graft material Previous attempts to repair the
CSF leak
FU
1 Ethmoid Left Combined Middle turbinate mucoperiostium + middle
conca bone
No 63
2 Ethmoid, cribriform
plate
Left Composite Dural substitute + middle turbinate No 71
3 Ethmoid, sphenoid
sinus
Right Combined Middle turbinate + abdominal fat Yes 29
4 Ethmoid, cribriform
plate
Right Combined Dural substitute + middle turbinate No 81
5 Ethmoid, posterior
wall of frontal sinus
Left Combined (Obliterative technique) dural substitute,
abdominal
fat, and turbinate bone in the sphenoid
No 14
Free simple graft of mucoperiostium from
the middle
turbinate in the pterygoid
FU Follow up (months)
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Mean hospitalization was about 1 week and mean
duration of follow-up was 36 months, with a range of 12
to 72 months. Normal MRI confirmed the total resolution
of symptoms (Fig. 2).
An outpatient endoscopic endonasal evaluation 1
month after the operation revealed that the skull
base defect had fully healed and that nasal mucosa had
returned to normal (Fig. 3). Breathing had also normalized.
Discussion
The diagnosis and treatment of anterior skull base defects is
a challenging problem [8]: the clinical suspicion of
meningoencephaloceles in children arises in the event of
monolateral nasal obstruction, while rhinorrhea and recur-
rent meningitis may suggest the presence of CSF leakage.
Endonasal evaluation is one of the first diagnostic tests
we routinely perform, using 2.7-mm diameter endoscopes
with 30° lenses. This procedure is easy to perform during
the MRI study and avoids having to resedate patients; it
allows us to evaluate the morphology of the nasal cavity
and to directly visualize active rhinorrhea or the presence of
a pulsating mass projecting into the nose.
The B2 transferrin dosage in the liquid sample collected
from the nose has a sensitivity of 97.7% [13–15]; this test is
rapid and requires just few milliliters of liquid [15–17]. One
limit of this test is that rhinorrhea must be active, and even
in cases of persistent rhinorrhea, it is not always easy to
collect the fluid sample, especially from pediatric patients.
Nowadays, spiral CT is the best imaging study for
localizing skull base defects as it is possible to obtain very
thin slices (0.5 mm) with a bone algorithm. The examina-
tion is very short so pediatric patients do not have to be
anesthetized. High-definition MPR allows for a complete
study in the axial, coronal, and sagittal planes in a supine
position; cistern CT, with the patients lying face down, is
used to localize the CSF leak in children with active
rhinorrhea after dye injection. CT evaluation of the
nasofrontal region is often difficult in the neonate because
the anterior skull base is largely cartilaginous at birth. It is
crucial to understand the CT appearance of this region in
the normal neonate and infant.
CT may be inadequate because small defects can be
missed through the partial volume effect, while the
detection of a small opening is not necessarily related to a
connection between the nasal mass and the intracranial
compartment. In difficult cases, acquisition of CT images
Fig. 3 a Endoscopic endonasal
repair of a meningoencephalo-
cele. b Outpatient endoscopic
evaluation after 3 months
Fig. 2 a Preoperative T1
sagittal MR study of a
congenital meningoencepha-
locele. b Postoperative T1
sagittal MR study after
endonasal endoscopic repair
Childs Nerv Syst
through the defect after intrathecal contrast administration
may determine soft tissue continuity with the subarachnoid
space; sagittal reconstruction of 1-mm images is optimal
[12]. One-millimeter axial and coronal CT is performed.
The coronal section has to be perpendicular to the hard
palate to show the entire temporal bone and exclude a
defect in the tegmen timpani or roof of the mastoid: in fact,
CSF flow from the middle ear or the mastoid through the
eustachian tube could simulate rhinorrhea. The CT pattern
can indicate whether there is a protrusion of cerebral tissue
into a meningeal sac or a tumor growing at the base. High-
resolution, 3-mm, axial, coronal, and sagittal MRI in T1-
and T2-weighted sequences is mandatory to formulate a
differential diagnosis. MRI is more sensitive than CT in
detecting a continuity between the nasal and cranial cavities
when there is a lesion with a very narrow neck; the
examination is also valuable in differentiating herniated
brain from inflammatory nasal masses, nasal gliomas, or
nasal dermal sinus cysts [1]. The signal intensity of nasal
gliomas is similar to that of both epidermoid tumors and
brain tissue; therefore, anatomic factors are more important
than signal characteristics in distinguishing between these
malformations. Meningoceles have a typical low signal in
T1 and a hyperintense signal in T2-weighted sequences.
Meningoencephaloceles have a typical brain-like signal of
the content in T2 sequences. Negative contrast enhance-
ment (gadolinium DPTA) rules out tumors. During neuro-
radiological studies, the middle and posterior cerebral fossa
are checked to exclude other congenital defects [18].
It is important to avoid any kind of biopsy during this
diagnostic phase; in the event of encephaloceles, this
manoeuvre could have serious consequences, namely,
cerebral injury, infections or rhinorrhea [19, 20].
All outpatients with posttraumatic CSF fistulas had a
preoperative fluorescein test: the fluorescein dyes the
cerebrospinal fluid, which becomes directly visible through
the endoscope, identifying the exact site of the leak.
Identification is aided by the use of a blue optical filter
system introduced into the light source for the endoscopic
equipment [9]. The fluorescein test was unsuccessful in
only one child with associated spinal trauma that may have
limited the normal diffusion of the dye. The fluorescein test
is essential to localize multiple CSF leaks. If the test is
positive, then surgery is mandatory.
The intraoperative fluorescein test was performed on all
our patients, allowing us to visualize the exact site of the
CSF rhinorrhea. No complications arose after injecting the
dy,e and the test appeared to be safe if performed following
the Graz school guidelines [7].
The direct paraseptal approach is performed in the event
of a meningoencephalocele in the olfactory groove that
lateralizes the middle turbinate; no other surgical procedure
on the ethmoid is carried out in these cases. In fact, if the
space on the cribriform plate is large enough to position the
graft, the middle turbinate is preserved and an autologous
graft is harvested from the nasal septum. The first step in
this surgical procedure is to reach and isolate the pedicle.
We found that a small neck is easier to repair not only
because of its size but also because the sac does not allow
important parts of the overlying central structures to
herniate. It is important to identify the correct layer to
separate the dura from the bone and perform the anatomical
dissection. The dura is often tightly adherent to the
underlying mucosa. The dura mater must be detached
thoroughly from the surrounding bone to fix the graft and
prevent recurrences during the child’s growth. The intra-
dural detachment of cerebral tissue adherence is obtained,
and a dural substitute is positioned using the underlay
technique under the bone (intracranially) and over the dura.
Thanks to the submucous access, the endoscope makes it
possible to dissect scarring tissue smoothly, minimizing
impact on the brain and conserving nasal and sinus mucosa.
An ethmoidectomy, with the excision of the middle
turbinate, is performed when the ethmoidal roof has to be
fully exposed to localize the CSF leak. This method is used
mainly to repair posttraumatic CSF leaks. Traumatic CSF
leaks involve multiple defect sites and the entrapment of
the dura mater in the rim of the fracture. In these cases, the
intraoperative fluorescein test is valuable to localize all the
defects, and the ethmoidal roof has to be drilled with a
diamond burr to completely expose the leak. The middle
turbinate is generally excised and used to harvest the bone
or the mucoperichondrial graft. The tear in the dura mater is
fully exposed, and all mucosa must be carefully removed
from the surrounding bone to fix the mucoperiosteum or
mucoperichondrial graft (free simple graft) over the bone
(overlay technique) and to prevent recurrences during the
child’s growth.
The transethmoidal–pterygoidal–sphenoidal approach is
used for defects in the lateral wall of the sphenoid sinus. We
used this approach in one patient, who had previously
undergone surgery at another hospital, to remove a left
parasphenoidal CSF cyst, position a subdural–peritoneal
drain, and carry out extracranial plastic repair of the skull
base of the middle fossa. Two CSF leaks were detected after
the pterygoid and anterior wall of the sphenoid sinus had
been fully exposed: one in the paralateral left side of the
sphenoid sinus, probably because the original graft onto
the skull base of the middle fossa had shrunk, and one in the
pterygoid due to abnormal pneumatization. After drilling
the bone to expose the two defects, the leak in the sphenoid
sinus was repaired with a dural substitute, abdominal fat, and
turbinate bone, while the leak in the pterygoid was repaired
with a free simple graft of mucoperiostium from the middle
turbinate. We believe that the choice of graft is essential for a
successful duraplasty. We generally use an autologous graft
Childs Nerv Syst
harvested from the nose to achieve a highly compatible
duraplasty. The mucoperiostium, from the middle turbinate,
and the mucoperichondrium, from the nasal septum, are
fashioned and positioned to fit the defect. Particular care
must be taken when implanting the graft: the mucosal part to
the nasal cavity and the periosteum to the skull base. It is
crucial not to obstruct the natural ostia of the paranasal
sinuses so as to respect and preserve normal sinus function.
Harvesting the graft from the nose avoids incising the
abdomen to obtain abdominal fat. If the area in the olfactory
groove is wide enough to position the graft, as in children
with a meningoencephalocele in the cribriform plate that
pushes the middle turbinate to one side, the middle turbinate
is preserved. The graft taken from the nasal septum is then
positioned with the underlay technique, and the mucoperi-
chondrium is used as overlay. Different nasal tissues and
other autologous tissue can be used to close the skull base in
particular situations [7, 21, 22].
We fixed the grafts with fibrin glue and hemostatic
sponges and did not observe any cases of graft displacement.
The absence of fluorescein flow through the graft during
the endoscopic test, using the Valsalva maneuver, reassures
the surgeon that the fistula was effectively repaired.
The main alternative to the endoscopic endonasal
technique is the transcranial approach.
A transcranial approach through a unilateral or bicoronal
bone flap allows the neck of the protruding brain tissue to be
isolated but requires a wider exposure with the retraction of
one or both frontal lobes. The intracranial repositioning of
the extruded tissue is difficult, and the repair of the dural
defect requires a larger graft. It is also difficult to control the
entire skull base defect without visualizing it directly. If an
endonasal approach is not used, the meningocele sac has to
be left in place, possibly causing breathing impairment and
requiring a second surgical procedure.
The limits of the extracranial endoscopic endonasal
approach depend on the characteristics of the endoscope:
loss of the third dimension in the surgical field and a long
learning curve. Failure of an endoscopic approach may
relate to the inability to successfully localize the defect,
inadequate preparation of the defect area for the graft
placement, the nature and amount of CSF leakage, the
nature and size of the graft, as well as graft displacement or
incomplete apposition of the graft to the skull base [23, 24].
The extension of the lesions can also be a limit for this
approach: fractures extending cranially or laterally out of
endoscopic view require a combined approach. A necrotic
or fibrotic meningoencephalocele or a large CSF-filled sac
may both be treated endoscopically: in the latter case by
draining and reducing the dimension of the sac and by
debriding the sac with its nonfunctional content in the
former. Large hernias with facial deformities require
combined transcranial endonasal approaches.
The goal of the endoscopic transnasal technique in
pediatric patients with a transethmoidal defect is to ensure a
stable duraplasty with minimally invasive surgery, avoiding
craniotomy. This less invasive technique is well-tolerated
by the child as clinical recovery is rapid and it requires only
a short stay in hospital.
Outpatient endoscopic evaluation, carried out 1 month
after the surgical procedure, usually demonstrates that nasal
mucosa has returned to normal without scars.
In conclusion, in children, the endoscopic endonasal
approach achieves the definitive repair of an anterior skull
base defect and preserves the normal function of the nose and
air sinuses with a very short inpatient period. It also reduces
the impact on the still-developing splanchnocranium.
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