Interhemispheric arachnoid cyst with agenesis of corpus callosum.

Arachnoid cysts are benign developmental cysts that occur throughout the cerebrospinal axis in relation to the arachnoid membrane and the subarachnoid space(l). Intracranial arachnoid cysts usually occur in close proximity to arachnoid cisterns, most often in the sylvian fissure(2) and they become symptomatic in early childhood(3). We report an interhemispheric arachnoid cyst associated with agenesis of corpus callosum in a neonate.