Middle cerebral artery fenestration.

Fenestration of the middle cerebral artery (MCA) is an unusual anomaly. We recognized and photographed MCA fenestration during an operation performed to clip an internal carotid artery aneurysm. The incidence of angiographic demonstration of this anomaly has been reported to be 0.26%. The clinical significance of fenestration of the vertebral and basilar arteries has primarily been the relationship of fenestration with other intracranial vascular anomalies. This is the first report of MCA fenestration associated with an aneurysm.