Surgical Treatment of Posterior Circulation Aneurysms - Anatomical Study and Surgical Technique

Posterior circulation aneurysms represent 10-15% of intracranial aneurysms. The diagnosis is usually secondary to subarachnoid hemorrhage due to its initial asymptomatic presentation and higher risk of rupture compared with aneurysms in the anterior circulation. The surgical treatment of posterior circulation aneurysms is complex and challenging for neurosurgeons because of the particular anatomy of the posterior circulation with its close relation to the brainstem and cranial nerves and also because of the depth and narrowness of the surgical approach. Aneurysms from different locations have specific anatomical relationships and surgical approaches for better visualization and dissection. Therefore, a detailed anatomy knowledge of the posterior circulation is mandatory for an individualized preoperative planning and good neurological and angiographic outcomes. We selected the main aneurysm sites on the posterior circulation, such as: posterior inferior cerebellar artery, basilar trunk, basilar bifurcation, posterior cerebral artery (PCA) and superior cerebellar artery for a detailed description of the relevant anatomy related to aneurysm, and the main surgical approaches for its surgical treatment. Furthermore, we performed a literature review with the most recent outcomes regarding to the surgical treatment of posterior circulation aneurysms. Resumo Aneurismas de circulacAo posterior representam de 10-15% dos aneurismas intracranianos. O diagnostico, frequentemente, e secundario a hemorragia subaracnoide devido a apresentacAo assintomatica na maioria dos casos e ao alto risco de sangramento comparado com aneurismas da circulacAo anterior. O tratamento cirurgico de aneurismas de circulacAo posterior e complexo e desafiador para os neurocirurgioes devido a anatomia particular da regiAo, profundidade do acesso cirurgico, e relacAo intima com o tronco encefalico e os nervos cranianos. Aneurismas de diferentes localizacoes tem diferentes relacoes anatomicas e, portanto, acessos cirurgicos especificos para melhor disseccAo e visibilizacAo de estruturas. Logo, um conhecimento detalhado de anatomia e mandatorio para planejamento operatorio individualizado e bons resultados clinico-radiologicos. Foram selecionadas as principais localizacoes de aneurismas de circulacAo posterior: Arteria cerebelar postero-inferior; tronco de arteria basilar, bifurcacAo de arteria basilar, arteria cerebral posterior, e arteria cerebelar superior para detalhamento anatomico da anatomia relevante. O estudo objetiva realizar uma revisAo da literatura dos principais resultados sobre tratamento cirurgico de aneurismas de circulacAo posterior, alem de descrever os principais pontos anatomicos relevantes a tecnica microcirurgica.