Angiographically occult vascular malformations causing intracranial hemorrhage.

In 5 patients, angiographically occult vascular malformations led to intracerebral or intracerebellar hemorrhages. Angiographic findings were not suggestive of vascular abnormalities, but signs of a mass were present in 4 patients. Computed tomography (CT) scanning suggested the presence of cryptic vascular lesions accompanied by intraparenchymal hemorrhage in 2 patients. In all patients surgical treatment was successful. Histological examination confirmed these lesions to be venous malformations in the cerebellum in 2 patients and in the left frontal region in 1, and arteriovenous malformations in the cerebellum and right putaminal region in 1 patient each.