Cryptic arteriovenous malformation of the choroid plexus of the fourth ventricle--case report.

A 54-year-old female presented with a cryptic arteriovenous malformation (AVM) of the choroid plexus of the fourth ventricle causing intraventricular hemorrhage. Computed tomography and magnetic resonance imaging disclosed the lesion near the fourth ventricle, but bilateral vertebral angiograms showed no abnormalities. The preoperative diagnosis was cavernous angioma. The mass was removed completely, and histological examination demonstrated an AVM of the choroid plexus. Vascular malformations of the choroid plexus of the fourth ventricle are extremely rare. The possibility of this lesion being the cause of primary intraventricular hemorrhage of unknown origin should always be considered.