[Clinical evaluation of subarachnoid hemorrhage of unknown etiology]

This study concerns 16 cases with spontaneous subarachnoid hemorrhage (SAH) of unknown etiology experienced in our department during a period from September 1979 through August 1986. SAH was confirmed by computed tomographic scanning (CT) or lumbar puncture. All cases were studied by four or three-vessel study. In the case of three-vessel study, adequate opacification of the posterior inferior cerebellar artery contralateral to the injected vertebral artery was considered as a necessary condition. Panangiography was repeated in all patients one to two weeks after the initial study and was negative. The severity of SAH in these patients on admission was relatively mild (Hunt and Kosnik grade I + II = 75%), and the degree of subarachnoid bleeding on CT was also mild. Medium to long-term outcome was excellent or good in 81% of cases, and none of them experienced rebleeding. Only one patient died of severe vasospasm on the 20th hospital day, but no aneurysm was found at autopsy. Illustrative 3 patients in whom the cause of SAH had been finally found was briefly reported. In the first patient, SAH was secondary to a paraventricular cryptic angioma. In the second patient, a microaneurysm had been concealed at the initial angiography by the parent arteries or intra-aneurysmal clot. In the third case of a fusiform aneurysm of the vertebral artery, the aneurysm proximal to the posterior inferior cerebellar artery could not be found at the first three-vessel angiography. Importance of CT and the necessity of repeat panangiography including magnification or oblique views so as not to over-look the causative vascular abnormalities were emphasized.