The corpus callosum: imaging the middle of the road.

Although the structure of the mammalian brain from species to species is relatively constant, unique to placental mammals is the corpus callosum. From the Latin ‘‘corpus callosum,’’ which means tough body, it is a crescent-shaped mass of white matter at the base of the longitudinal fissure that connects the cerebral hemispheres and is the main passageway for commissural fibers. Its 4 named parts are the rostrum, genu, body, and splenium. Insults to the corpus callosum can be congenital or acquired. The latter can be subdivided into neoplastic, traumatic, vascular, demyelinating, and miscellaneous etiologies. In this pictorial essay, we present pathologies that involve the corpus callosum diagnosed with computed tomography (CT) and magnetic resonance (MR).