Type: Educational Exhibit

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Differential diagnostic points of defect of the corpuscallosum : congenital versus acquired.

Poster No.: C-0241

Congress: ECR 2011

Type: Educational Exhibit

Authors: J. H. Yoo; Seoul/KR

Keywords: Education, MR, Head and neck, Anatomy

DOI: 10.1594/ecr2011/C-0241

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Learning objectives

To display specific imaging features of many congenital anomalies of corpus callosumand to learn the differential points from the acquired defects based on the understandingembryologic and pathophysiologic background.

Background

The corpus callosum is a large dense white matter tract connecting the two cerebralhemispheres. Many congenital lesions of the corpus callosum have very unique findings.The pattern of affecting the corpus callosum is different from congenital and acquireddefects. In order to understand those diseases, it is essential to understand the basicconcepts of commissural development.

Embryology Overview : Embryologically, corpus callosum begins to develop about 7-week gestation, and callosal plate is detected by 14weeks and the adult form is virtuallycomplete by 20-week.of gestational ages. It gradually increases in thickening and lengthduring the 1st year, reaching adult thickness by the 6th or 9th year (Fig.1). It is composedof four portions: rostrum, genu, body, and splenium. There has been debate aboutthe sequence and timing of the development of the corpus callosum. Generally it wasaccepted that the corpus callosum starts with the development of the genu; the bodyand splenium develop later. The rostrum was thought the last part of the development.However, recent studies based on diffusion tensor imaging (DTI) demonstrated that therostrum was already present at around the 15weeks of gestational age with the genu andanterior part of the body.

Imaging findings OR Procedure details

Agenesis of corpus callosum(ACC). ACC is a relatively frequent malformation. Twotypes of ACC can be distinguished morphologically: Type 1 ACC, in which axons arepresent but are unable to cross the midline; they form large aberrant longitudinal fiberbundles (Probst bundles) (Fig.1). Type 2 ACC, apparently less frequent, in which axonsfail to form; therefore no Probst bundles are found.

Hypogenesis of corpus callosum. If the normal developmental process of corpuscallosum is disturbed, it may be completely absent or hypogenetic. For the understandinghypogenesis of corpus callosum, basic knowledge of developmental sequence is

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absolutely required. When the corpus is hypogenetic, the earlier formed genu and anteriorbody will be formed but later formed splenium will not (Fig.2.-Fig.4).

Dysgenesis of the corpus callosum is defined as malformation which usually occursas a result of an injury during formation of its precursors rather than from an injury to thecorpus itself. This failure may result from either extrinsic causes (lipoma, interhemisphericcyst, etc…) (Fig.5), from disorders in neuronal migration, or intracortical disposition linkedwith gyral anomaly.

Congenital diseases associated with corpus callosal abnormality.

Most of the cerebrum and cerebellum form at the same time as the corpus callosumbetween 8-20 wks of gestational age. Therefore, anomalies of the corpus callosumare often associated with other cerebrum and cerebellar anomalies,commonly ChiaryII malformation, holoprosencephaly, migration anomaly, midline facial syndrome, andDandy-Walker malformation (Fig.6-8). Callosal anomalies also can be part of syndromeand also can be associated with metabolic diseases. Holoprosencephaly is known theonly brain malformation in which the posterior corpus callosum can be formed in theabsence of anterior callosal formation (Fig.9). The corpus callosum is already formed inthe migration stage and the corpus callosum appears intact or dysgenetic in appearance(Fig.10).

Acquired dysplasia or defect of corpus callosum is not rare in the prematuritysequellae related hypoxic periventrticular leukomalacia or status epilepticus orcorticospinal tract injury (Fig.11-14). Axonal injury related trauma can be resulted insecondary defect of corpus callosum (Fig.15-17).

Images for this section:

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Fig. 1: Agenesis of corpus callosum. Typical radiating medial sulci into the 3rd ventricle,everted cingulated gyrus enable to cross the midline forming Probst bundle, andcolpocephaly.

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Fig. 2: Hypogenesis of corpus callosum with a small dot of corpus callosal genu only.

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Fig. 3: Hypoplasia of corpus callosum with genu and anterior body formation.

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Fig. 4: Partial agenesis of splenium and rostrum with the genu and major portion of bodyremaining.

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Fig. 5: Lipoma with corpus callosal anomaly. Severe hypogenesis of corpus callosumwith anterior pericallosal lipoma. Posterior pericallosal lipoma with mild hypoplasia ofsplenium.

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Fig. 6: Corpus callosal anomaly with posterior fossa anomaly. Intact genu and anteriorbody but diffuse dysplastic change of corpus callosum with thin body and splenium inChiary II malformation.

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Fig. 7: Hypogenesis of corpus callosum in the rhombencephalosynapsis. Inferiorherniation of dysplastic cerebellum into the foramen magnum. Axial scan showsdysplastic and fused both cerebellar hemisphere. Corpus calloshum shows intact genuand anterior body, but absent posterior body and splenium.

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Fig. 8: Diffuse thinning corpus callosum in the Dandy-Walker malformaion. Hypoplasisof vermis and cerebellum with prominent posterior fossa CSF spaces.

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Fig. 9: Holoprosensephaly with absent genu of corpus callosum but presence of posteriorbody and splenium. It is known the only brain malformation in which the posterior corpuscallosum can be formed in the absence of anterior callosal formation.

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Fig. 10: Mild notch of corpus callosum in the closed-lip schizencephaly. . There is bilateralclosed-lip type schizencephaly defect in the parietal lobes and extensive polymicrogyria.Corpus callosum shows relatively intact in shape except focal defect at the anterior bodyportion. The corpus callosum is already formed in the migration and sulcation stage andthe corpus callosum appears intact or mild dysgenetic in this stage arrest.

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Fig. 11: Acquired focal defect of anterior body of corpus callosum with only small islandsof a genu and mid body formed in static encephalopathy.

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Fig. 12: Diffuse thinning posterior body and splenium of corpus callosum due tocorticospinal tract injury in the splastic dysplegia

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Fig. 13: Diffuse thinning genu and anterior body of corpus callosum in sequellae ofperinatal ischemic insult but relatively intact posterior body and splenium, which can beembryologic differential points from the congenital dysgenesis.

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Fig. 14: Diffuse atrophy of corpus callosum in the extensive hypoxic perinatal injury.Extensive cystic encephalomalatic change of bilateral cerebral hemisphere with darksignal hemosiderin deposits. Diffuse loss of brain tissue including white matter andsecondary atrophic change of corpus callosum.

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Fig. 15: Diffuse atrophy with multifocal defect of corpus callosum in the shakenbaby syndrome. Chronic subdural hemorrhage is noted along the bilateral cerebralhemisphere. Corpus callosum shows intact but diffuse thinning suggestive diffuse volumeloss and multifocal defects possibly suggestive axonal defect/loss.

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Fig. 16: Acquired defect of the corpus callosum in the non-accidental injury(NAI).Irregular shaped cystic defect of the genu and anterior body of the corpus callosum withbilateral subdural collection.

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Fig. 17: Acquired defect of corpus callosum related with ventriculoperitoneal shunt in thecerebral palsy. Patient has former prematurity and cerebral palsy history. Large defect ofcorpus callosal body is noted probably due to defect by VPS tube. Accompanying diffuseatrophy of posterior body and splenium is related with cerebral palsy. Intact genu is noted.

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Conclusion

Corpus callosum shows characteristic findings in the congenital and acquired defect.Knowledge of the embryologic developmental sequence of the corpus callosum is helpfulto understand these changes.

Personal Information

1. Jeong Hyun Yoo, M.D., Depatmen of Radiology, Mokdong Hospital, Ewha womansuniversity, School of medicine, Seoul, Korea.

2. Jill V Hunter, MD., Diagnostic Imaging, Texas Childrens Hospital, Baylor College,Houston, Tx, USA.

References

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2. Ren T, Anderson A, Shen WB, Huang H, Plachez C, Zhang J, Mori S, Kinsman SL,Richards LJ. Imaging, anatomical, and molecular analysis of callosal formation in thedeveloping human fetal brain. Anat Rec A Discov Mol Cell Evol Biol 2006;288(2):191-204.

3. Volpe P, Campobasso G, De Robertis V, Rembouskos G. Disorders of prosencephalicdevelopment. Prenat Diagn 2009;29(4):340-354.

4. Barkovich AJ. Magnetic resonance imaging: role in the understanding of cerebralmalformations. Brain Dev 2002;24(1):2-12.

5. Georgy BA, Hesselink JR, Jernigan TL. MR imaging of the corpus callosum. AJR AmJ Roentgenol 1993;160(5):949-955.

6. Uchino A, Takase Y, Nomiyama K, Egashira R, Kudo S. Acquired lesions of the corpuscallosum: MR imaging. Eur Radiol 2006;16(4):905-914.

7. Truwit CL, Barkovich AJ. Pathogenesis of intracranial lipoma: an MR study in 42patients. AJR Am J Roentgenol 1990;155(4):855-864; discussion 865.

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