SURGERY FOR ANGIOGRAPHICALLY OCCULT CEREBRAL ANEURYSMS

In 15% of patients with spontaneous subarachnoid hemorrhage (SAH), the source of bleeding cannot be determined despite repeated cerebral ang iography. However, some patients diagnosed as having ''SAH of unknown cause'' actually harbor undetected aneurysms. The authors report six p atients with SAH who, despite multiple negative cerebral angiograms, u nderwent exploratory surgery due to a high clinical and radiographic s uspicion for the presence of an aneurysm. Brain computerized tomograph y (CT) scans revealed blood located mainly in the basal frontal interh emispheric fissure in four patients, in the sylvian fissure in one pat ient, and in the interpeduncular cistern in one patient. The patients were evaluated as Hunt and Hess Grades I to III, and had undergone at least two high-quality cerebral angiograms that did not reveal an aneu rysm. Vasospasm was visualized in two patients. Three patients rebled while in the hospital. Exploratory surgery was performed at an average of 12 days post-SAH. Five aneurysms were discovered at surgery and we re successfully clipped. All four patients with interhemispheric blood were found to have an anterior communicating artery (ACoA) aneurysm. The patient with blood in the sylvian fissure was found to have a midd le cerebral artery aneurysm. These aneurysms were partially thrombosed . No aneurysm was detected in the patient with interpeduncular SAH, de spite extensive basilar artery exploration. Five patients had an excel lent outcome and one patient developed diabetes insipidus. These resul ts show that exploratory aneurysm surgery is warranted, despite repeat ed negative cerebral angiograms, if the patient manifests the classica l signs of SAH with CT scans localizing blood to a specific cerebral b lood vessel (particularly the ACoA) and if a second SAH is documented at the same site.