[Partial fenestration of the basilar artery--report of a case (author's transl)].

A 44-year-old male entered the hospital following an episode of subarachnoid hemorrhage on January 28, 1975. The left vertebral angiography revealed an anteriovenous malformation in the mesencephalon mainly feeded by the thalamoperforate artery and the medial branch of the posterior choroidal artery. A partial fenestration of the basilar artery was also demonstrated. The patient refused the surgical treatment for the arteriovenous malformation and was discharged on March, 28, 1975. Fenestration of the basilar artery develops by arrested or abnormal development at the first and second stage of the embryological process. Most basilar artery fenestration demonstrated by brain dissection and angiography are cases of a short segment duplication (partial fenestration) while duplication of the entire segment of the basilar artery (complete fenestration) is quite rare. Only six cases of angiographically revealed basilar artery fenestration have been reported so far in the literature. With increasing application of vertebral angiography, this developmental anomaly may be encountered more frequently.