Aneurysms of the medullary segments of the posterior-inferior cerebellar artery: considerations on treatment strategy and clinical outcome.

Proximal aneurysms of the medullary postero-inferior cerebellar artery (PICA) tract are peculiar due to critical anatomical location, small size and tortuosity of the parent vessel, close origin to brainstem perforators, and fragility of the sac wall. Moreover, most patients present after bleeding, increasing the challenges. Aim of this study is to evaluate the treatment modality and outcome of these patients during the last decade at the University Clinic of Torino. Databases of the Neurosurgical and Neuroradiological Department of the University of Torino were analyzed to retrieve patients treated for aneurysms of the medullary PICA tract. Charts and neuroradiological documentation were revised to complete the database. Of 621 patients treated for an intracranial aneurysm, 23 had PICA aneurysm, 18 located at the medullary tract. Only two were unruptured and 16 were ruptured aneurysms. Sixteen underwent endovascular treatment and two underwent surgery. In six cases the aneurysm was cured by parent vessel occlusion. At 6 months follow-up, the Glasgow outcome scale was high (5 and 4) in 16 patients; two patients had died in the acute phase, for reasons unrelated to the procedure. If not adequately compensated, parent vessel occlusion associates with high risks of ischemia and related brain swelling. In the present series sufficient collateral flow contributed to a good tolerance toward occlusion in all cases. Despite the small size of the present series, most treated cases presented a good outcome. Nevertheless, distal revascularization of the occluded artery would be indicated where collateral flow is insufficient.