Occult cerebral arteriovenous malformations.

Angiographically occult arteriovenous malformations in the brain are rare but cause considerable diagnostic difficulty. Four personal cases are presented in which CT scans showed hypodense lesions with minimal or no enhancement, and angiograms showed only an avascular mass. Gliomas, a dermoid and an infarct were suspected before histological examination of biopsies or excised specimens. The patients had presented in early adult life with epilepsy and focal deficits.