Name : Morteza
Family :Sanei Taheri
Affiliation : Radiology Department,Shohada Tajrish Hospital,SBMU
Academic Degree: Associate Professor of Radiology
Resident : Hussein Soleiman Tabar
Gender : Male
Age : 8
8-year-old boy with mental retardation and seizure
Imaging Procedures and Findings
Partial agenesis of corpus callosum is evident. Medial sulci of the posterior portion of the hemisphere are radially arranged perpendicular to the narrow inferior margin of the hemisphere (image 5). There is a paucity of sulcation with slightly increased cortical thickening on the left side consistent with pachygyria (best shown on image 3). Aneurysmal dilatation of vein of Galen is noted as well (images 2 and 6).
The corpus callosum forms from front to back and myelinates from back to front. Following these principles, partial agenesis of the corpus callosum will result in formation of the genu and anterior body and absence of the posterior body and splenium. Two conditions deviate from the typical callosal agenesis appearance. Both secondary destruction of the corpus callosum and holoprosencephaly can result in nonsequential segments of absent callosum. The imaging appearance of callosal dysgenesis is variable, ranging from complete to partial absence of callosal tissue. Concomitant with the absence of the corpus callosum is failure of eversion of the cingulate gyrus, with lack of cingulate sulcus formation. The medial hemispheric sulci extend to the third ventricle, which on a sagittal image results in a radial, spoke-wheel appearance of the gyri along the interhemispheric fissure. Without the supporting deep white matter fibers, there is alteration in the configuration of the ventricles, with the frontal horns taking on a steer-horn appearance in the coronal plane and a racing car appearance in the axial plane. This is the result of redirection of longitudinal callosal fibers (Probst bundles) along the medial ventricular walls. Additionally, because of the redirection of the Probst bundles and decrease in posterior white matter, there is dilation of the occipital horns, called colpocephaly. Interhemispheric cysts may be seen, frequently in communication with the third ventricle.
Partial agenesis of corpus callosum, aneurysmal dilatation of vein of Galen, pachygyria
Brant WE, Helms CA: Fundamentals of Diagnostic Radiology, 3rd ed. Philadelphia: Lippincott Williams & Wilkins, 2007.