Venous malformation of the pineal region.

A single and perhaps unique case of a venous malformation over the quadrigeminal plate causing acute obstructive hydrocephalus is reported. The lesion was well demonstrated by means of CAT scan but cerebral angiography failed to reveal the vascular nature of this lesion. Complete thrombosis of the lesion was achieved by surgical intervention and the resolution of the lesion was demonstrated by CAT scan. The patient remains asymptomatic and neurologically intact six months after the operation.