Surgical treatment for subarachnoid hemorrhage of unknown etiology: consideration of radiological findings of digital subtraction angiography.

At present, conventional intra-arterial angiography remains the gold-standard for the diagnosis of etiology of subarachnoid hemorrhage (SAH), but this may change as intra-arterial digital subtraction angiography (IA-DSA) or three-dimensional computerized tomography (CT) angiography improve. The purpose of this study is to investigate the reliability of IA-DSA for the diagnosis of SAH of unknown etiology. Of 184 patients admitted to our unit with proven spontaneous SAH between January, 1994, and March, 1997, 124 underwent IA-DSA. Ten were diagnosed as having SAH of unknown etiology by initial angiography; therefore, the incidence of SAH of unknown etiology based on the diagnosis of initial IA-DSA was 8.1%. Of these 10 patients, six patients were treated conservatively in the acute period. Other four patients underwent exploratory surgeries in the acute period due to a great suspicion of the presence of aneurysms. In one patient, no aneurysm was detected; in three patients aneurysms were discovered at surgery and successfully clipped. In two of three patients, aneurysms were not discovered at the suspected site, because radiological findings of a thrombosed aneurysm and infundibular dilatation of a perforator caused incorrect diagnosis of the aneurysm sites. Although the site of aneurysm diagnosed by IA-DSA is not always correct, exploratory aneurysm surgery during the acute period based on the diagnosis by IA-DSA is warranted, and IA-DSA is acceptable for the diagnosis of SAH of unknown etiology.