Magnetic resonance imaging of idiopathic herniation of the cuneus gyrus.

A 65-year-old woman presenting with chronic headaches and without overt visual symptomatology was found to have herniation of the cuneus gyrus into the superior cerebellar cistern. Only one prior case of idiopathic brain herniation has been described, in which the parahippocampal gyrus herniated into the ambient cistern. In that case a biopsy was performed as the herniation was mistaken for a tumor. We describe the features of idiopathic brain herniation that would mitigate the necessity for undergoing brain biopsy.