MR imaging of callosal and corticocallosal dysgenesis.

Callosal dysgenesis implies a malformation of the corpus callosum with origins in the embryogenesis of the telencephalon. A retrospective review of 15 cases of callosal dysgenesis revealed three distinct categories: agenesis (three subjects), hypogenesis (nine subjects), and hypoplasia (three subjects). The basis of this distinction rests upon considerations of neural tube closure, formation and maintenance of the inductive plate of the massa commissuralis, and migration of the neuronal elements of the cerebral cortex responsible for the projection of the commissural fibers of the corpus callosum. These processes are somewhat interdependent in their expression and consequence, resulting in a unique mosaic of callosal and cortical gray matter and hemispheric white matter configurations that have individually varying clinicoradiologic manifestations.