Callosal Agenesis

5-year-old male with history of agenesis of the corpus callosum. On the 3D-sagittal T1-weighted image, there is absence of the corpus callosum. There is also a radial gyral appearance of the cingulum and a high-riding third ventricle. On the axial FLAIR and T2-weighted images, there is a parallel configuration of the lateral ventricles which have a colpocephalic appearance. There are Probst bundles also demonstrated on the axial T2-weighted and color-coded fractional anisotropic images. The absent corpus callosum is also noted on the first color-coded anisotropic map. Corpus callosal abnormalities range from primary agenesis to secondary dysgenesis. Incidence is approximately 1:20,000 with a male to female ratio of 2:1. Associations include trisomies, numerous syndromes such as fetal alcohol and Gorlin syndrome, Chiari II, Dandy-Walker, and the mucopolysacchharoidoses among many other causes.