Angiographically occult arteriovenous malformations.

Angiographically occult arteriovenous malformations not associated with clinically recognizable intracranial hemorrhage appear to be rare. We are reporting three cases of histologically proven arteriovenous malformations of the brain that were angiographically occult. These cases presented with seizures or attacks of dizziness, and were detected by computed tomography scan, radionuclide scan, or both. The preoperative diagnosis was granuloma in the first case and meningioma in the other two. After surgical exploration, biopsy revealed an arteriovenous malformation in each case. A review of 47 cases in the literature is tabulated and etiologies of the angiographically occult arteriovenous malformations are discussed. The routine use of computed tomography scan and timely, appropriate surgical intervention with the operating microscope for the removal of these deeply situated lesions is necessary for the diagnosis and therapy.