Analysis of the Safety and Advantage of Ligation/Transection of the Superior Sagittal Sinus at the Level of Crista Galli: Basal Interhemispheric Approach for Anterior Communicating Artery Aneurysms

Introduction: Anterior communicating artery (A com) aneurysms are most frequently clipped by pterional approach or trans-sylvian approach with or without some modifications, and they are much less frequently clipped by anterior/basal interhemispheric approach because of unfamiliarity to these approaches. The basal interhemispheric approach includes a ligation/transection of the superior sagittal sinus (SSS) and exposure/cranialization of the frontal air sinus, which allows wider working space for safe clipping without significant brain retraction. Thus, this approach is safer and better for high-positioned or large/giant A com aneurysms. There is a concern for venous infarction by the occlusion of the SSS. We retrospectively reviewed 42 consecutive cases and evaluated the safety of the SSS ligation at the skull base.

Methods: After a bifrontal craniotomy and cranialization of the frontal air sinus, the SSS was ligated and transected at the most proximal part at the level of the crista galli in all the 42 cases. Then the falx was also cut all the way down to the interhemispheric fissure. The interhemispheric fissure was dissected and split by using the usual sharp dissection technique and brain holding with minimum retraction under microscope and clipped aneurysms.

Results: Forty-two cases (20 males and 22 females with a mean age of 55.26 years) were reviewed. Total 25 aneurysms were ruptured and 17 were unruptured. Total 27 aneurysms were less than 10 mm, 12 were 10 to 20 mm, and 3 were greater than 20 mm. Twenty-three aneurysms were located higher than 10 mm from the anterior skull base. The A1-Acom-A2 complex was well exposed in all cases. Bilateral A2 and A3 segments were exposed well. All the aneurysms were dissected and exposed for safe and complete clipping. By cutting the falx and SSS, a wider working space was obtained without brain holding but not retraction compared with the conventional anterior interhemispheric approach. The hypothalamic arteries were easily identified through this approach even with large/giant or posterior projecting aneurysms. In four ruptured cases, the bilateral A1 and A2 segments were temporarily occluded without difficulty. No patient had venous congestion or infarction associated with the ligation/transection of the SSS at the base of the skull adjacent to the crista galli in all cases.

Conclusion: Ligation and transection of the SSS is safe and provides wider enough for safe clipping of A com aneurysms. Basal interhemispheric approach is unfamiliar to many vascular neurosurgeons, but once surgeons have knowledge about the required microsurgical anatomy and technique, this approach can be very useful for A com aneurysms which are challenging by the conventional pterional/trans-sylvian approach, such as large/giant, superiorly/posterior projecting, and high-positioned ones.