Entry Point to the Sylvian Fissure for the PterionalTranssylvian Approach in Aneurysmal Subarachnoid Hemorrhage

Background: Although the anatomy of the Sylvian fissure is understood, there is littleinformation where to start its dissection in the pterionaltranssylvian (PT-TS) approach. At small craniotomy using the PT-TS approach, we set the entry point tothe Sylvian fissure at 15 mm behind the anterior edge of the craniotomy along theSylvian fissure and designated this site “point 15.” Here we compared the utility ofpoint 15” with the Sylvian point (point on the Sylvian fissure giving rise to the horizontaland anterior ascending rami) that had been recommended earlier as the entry site foropening the Sylvian fissure. Materials and Methods: This study includes 15 patients withruptured anterior circulation aneurysms. We evaluated the usefulness of “point 15” in the PT-TS approach for aneurysmal neck clipping with respect to the adequacy of anatomical exposure and low invasiveness. Results:In8 patients “point 15” provided for excellent anatomical exposure of theSylvian fissure; complete neck clipping was possible with minimal brain retraction and damage. Conclusions: The “point 15” was an easily set entry point to the Sylvian fissure. Itprovided for sufficient anatomical exposure at surgery for anterior circulation aneurysms. key words : sylvian fissure, entry point, transsylvian approach.