Vascular anomalies and subarachnoid haemorrhage associated with persisting embryonic vessels.

In 25 per cent of patients with persistinc primitive trigeminal artery, and in 27 percent of patients with primitive hypoglossal artery, vascular malformations or a history of subarachnoid haemorrhage were found. There is a high incidence of aneurysms at the site of origin of the persisting embryonic vessels. No relation was found between the persisting embryonic vessels and the age, sex, and time of subarachnoid haemorrhage. Opacification of posterior cerebral arteris, vertebral arteries, and posterior communicating arteries was analysed, and variations of the Circulus arteriosus Willisi were found. Ten patients with persisting embryonic vessels are described. In patients in whom external carotid-middle cerebral artery bypass is planned, attention should be drawn to the possibility of persisting embryonic vessels.