[Abnormal fusion of 2 primitive trigeminal arteries: apropos of an anatomo-radiological case].

Agenesis of the internal carotid artery was discovered during emergency cerebral angiography carried out on a comatose 28 year old man. The left cerebral hemisphere was supplied from the controlateral carotid artery, via a large vessel running through the sphenoid bone, between the intracavernous portions of the internal carotid arteries. Postmortem examination showed that death resulted from massive haemorrhagic infarction of the cerebellum and brain stem. Absence of the cervical and petrosal portions of the left internal carotid artery was confirmed. The anastomotic vessel was found to run through the spongiosa below the dorsum sellae. The heart, major vessels and circle of Willis were otherwise normal. An intercarotid anastomosis of this type has been reported on three previous occasions, in none of which was there anatomical confirmation.