A case of angiographically demonstrated fenestration of the internal carotid artery in association with an aneurysm arising from the anterior communicating artery is reported.
The patient was a 58-year-old man and was admitted because of consciousness disturbance. The patient was semicomatose, and the neurological examination revealed nuchal stiffness and bilateral retinal hemorrhage. Right carotid angiography showed an aneurysm of the anterior communicating artery and fenestration of the internal carotid artery.
Fenestration of the vertebral artery at its origin was well known. However, no previous reports of angiographically demonstrated fenestration of the internal carotid artery were seen among 43 cases of fenestration in Japanese subjects found in the literature. Only a case of duplication of the internal carotid artery was reported in U.S.A.
In the authors' case, fenestration of the internal carotid artery started at 15 mm distal to its bifurcation or at the level of the second vertebra. This fenestration presumably developed by anomalous connection of the third aortic arch with the dorsal aorta, or by persistence of the cranial part of the ductus caroticus.