Other Congenital Malformations

Malformations of the corpus callosum occur in complete or partial forms. Callosal formation proceeds from anterior to posterior, and thus in partial agenesis the anterior portion is typically preserved, as in Fig. 25.1A (although, in this instance, only a very small part of the corpus callosum is present). In this figure the cingulate gyri are aligned progressively radially in the posterior direction where the cingulate sulcus has not formed secondary to callosal absence. One gyrus extends to the cortical surface. In neonates, in whom the callosum is not readily visualized, radiating gyri may be diagnostic of agenesis. Mega cisterna magna (Fig. 25.1A), Chiari type 2, and Dandy-Walker malformations may be seen with agenesis. Parallel lateral ventricles (Fig. 25.1B

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