Chapter 51 - Surgical Management of Midbasilar and Lower Basilar Aneurysms

Abstract

Mid and lower basilar artery aneurysms comprise less than 5% of intracranial aneurysms and involve the anterior inferior cerebellar artery (AICA), lower basilar trunk, and vertebrobasilar junction (VBJ). This chapter highlights the various surgical approaches used for clip reconstruction of these complex aneurysms. The complexity of these microsurgical procedures is attributable to a restrictive, small surgical window encircled in thick bony skull and surrounded by critical neurovascular structures of the brainstem. Delicate dissection and microsurgical clipping in this region require careful preservation of the numerous perforating arteries arising from the basilar trunk and supplying the brainstem. In recent years, there has been a shift toward endovascular therapy for complex mid and lower basilar aneurysms. However, there continues to be a critical role for microsurgical clipping for certain basilar aneurysms with or without bypass. Surgical approaches include extended retrosigmoid, transpetrosal, far lateral, combined supratentorial-infratentorial, and anterior transclival approaches. The transpetrosal approaches can be further subdivided into retrolabyrinthine, translabyrinthine, and transcochlear approaches. The extended retrosigmoid approach is the one most commonly used for VBJ or AICA aneurysms. The far lateral approach provides the best exposure of the vertebral artery, posterior inferior cerebellar artery, and VBJ aneurysms. The transpetrosal approaches are used for accessing the cerebellopontine angle and afford varying degrees of hearing preservation. For treatment of larger or more complex basilar aneurysms, the combined supratentorial-infratentorial approach can be used. The anterior transclival approach is rarely used because it is associated with a high risk of cerebrospinal fluid leak and meningitis.