Fenestration of the posterior communicating artery.

A 21-year-old male presented with sudden onset of right-sided third nerve paresis. Angiogram showed a fenestrated posterior communication artery on the right side and no other vascular anomalies. There was no other lesion that could suggest a cause for the third nerve weakness. Fenestration of the posterior communicating artery has not been reported till date. The case is discussed and the literature on the subject is reviewed.