The angiographically occult cerebrovascular malformation. Report of three cases.

Three cases presenting with hemiparesis, headache, or seizures gave no history suggestive of subarachnoid or intracerebral hemorrhage. Carotid arteriograms were performed, and in each case failed to demonstrate a vascular malformation. In all three cases cerebral lesions were shown by either computerized tomographic (CT) scan, radionuclide scan, or both. Surgical exploration and biopsy revealed a vascular malformation in each case. The CT scans in two of the cases showed dense lesions that could suggest vascular malformation as a diagnostic possibility.