Rupture of posterior inferior cerebellar artery by single blow to head.

Two cases of isolated traumatic subarachnoid hemorrhage from the posterior inferior cerebellar artery are described. The rupture was caused in one instance by a fist blow to the face and in the other by a kick to the head. One patient survived for three days, the other patient for three weeks. In the latter patient, intimal fibrosis was progressing and the brain stem was partly infarcted. Necrosis and fragmentation of the wall adjacent to the rupture suggested both devitalization due to stretching and jarring as pathogenetic mechanisms. These lesions can be distinguished from berry aneurysms by their location along the trunk of the artery instead of in the fork of the bifurcation, by the lack of a fibrous aneurysmal sac, and often by fragmentation of the arterial wall at the edge and also near and opposite the rupture.