High Position Basilar Top Aneurysm Treated via Third Ventricle

There are two major approaches to a basilar top aneurysm: one is the subtemporal method developed by Drake, and the other is the pterional method developed by Yasargil. In either approach, however, it is hazardous and difficult to approach a basilar top aneurysm with megadolichobasilar anomaly because strong retraction of brain, nerve and vessel is required. A case of a ruptured basilar top aneurysm with megadolichobasilar anomaly successfully treated directly through the third ventricle is reported. A 62-year-old woman was admitted with consciousness disturbance. A plain CT scan on admission demonstrated massive and diffuse subarachnoid hemorrhage and a clot in the third ventricle. The left vertebral angiography demonstrated a 5×5mm basilar top aneurysm with megadolichobasilar anomaly 24mm distant from the dorsum sellae. The aneurysm was considered to be inaccessible by conventional approaches because of its high position. Therefore, we applied a new approach, described below. The operation was performed two days after the onset of symptoms, using a bifrontal craniotomy. Dissecting the interhemispheric fissure, we approached the third ventricle via the lamina terminalis. Evacuating the clot in the third ventricle, the basilar top aneurysm was visualized. After dissecting the neck of the aneurysm and perforators, clipping was performed. The postoperative course was uneventful. The surgical key points and the prospective view in approaching via the lamina terminalis and through the third ventricle for a high position basilar top aneurysm are discussed in this paper.