Partial agenesis of the anterior corpus callosum: correlation between appearance, imaging, and neuropathology.

Two patients with partial (semilobar) holotelencephaly are reported with apparent partial agenesis of the corpora callosa. These patients are of interest because they appear to possess the posterior portion of the corpus callosum but not its anterior component. Because the corpus callosum develops in the commissural plate rostrally and is elaborated in a rostral-caudal gradient, this apparent lack of the rostral component is embryologically puzzling. The neuropathologic studies of 1 patient resolved the apparent discrepancy between magnetic resonance imaging and embryology of the corpus callosum. With these data, we addressed the embryologic factors that may explain this malformation.