Acquired hump of the corpus callosum: a rare morphologic complication after CSF shunting.

Congenital hydrocephalus, chronic ventricular over-shunting, white matter volume loss, and lateral ventricle communication were common to all cases. Corpus callosum length was above normal values. The corpus callosum hump term was previously described as dysplasia but was not present on initial scans in our cases. We conclude that the corpus callosum hump can be acquired as a complication of over-shunting in children with congenital hydrocephalus. Thus, we present our examples as "acquired hump of the corpus callosum," which differs from the prior example. We postulate that the lengthening of the stretched corpus callosum due to chronic hydrocephalus in the pre-myelinated state renders it unable to return to its normal shape when the ventricles are drained. Over-shunting of both lateral ventricles simultaneously in the absence of a septum pellucidum results in collapse and folding in of the corpus callosum on itself, resulting in the hump.