Angiomatous are usually unilateral, but bilateral involvement may occur. Melanosis of the leptomeninges has been observed in some cases. Cerebral vascular abnormalities usually result in inadequate blood supply to the superior sagittal sinus. Associated cerebrovascular anomalies may include enlargement and tortuosity of the subependymal and medullary veins, distorted course of the cerebral veins, arteriovenous malformations, arterial thrombosis, abnormal external carotid arteries, and subdural hematoma. Intracranial calcificataions occur in about half of all cases.
Recurrent headaches are common but hemiperesis is infrequent.
The syndrome is mostly sporadic but familial occurrence has been reported. Listed in NIM in the autosomal dominant catalog.