LAUSR

BACKGROUND True posterior inferior cerebellar artery (PICA) aneurysms outside the vertebral artery-PICA (VA-PICA) region are rare, with approximately 30 cases reported in just a few papers; no treatment paradigm has been advocated. The objective of this study was to present detailed clinical features and outcomes for several treatments for true PICA aneurysms and suggest an algorithm for treatment strategies. METHODS We retrospectively analyzed outcomes of patients treated for PICA aneurysms with microsurgical and endovascular treatments. We also investigated the influence of several factors on the modified Rankin Scale (mRS) score. RESULTS Cases with PICA aneurysms (n=36) outside the VA-PICA region were identified angiographically. Aneurysm locations included anterior medullary (n=7), lateral medullary (n=10), tonsillomedullary (n=4), telovelotonsillar (n=12), and cortical (n=3) segments of the PICA. Aneurysm morphology was as follows: dissecting: 22; fusiform: 6; saccular: 8. On multivariate analysis, age (P=.028) and lack of vermian infarction (P=.037) were associated with a significantly better prognosis. Prognosis was not significantly different for the five aneurysm locations and among the four treatment groups: clipping/coiling, trapping/parent artery occlusion (PAO), trapping/PAO+bypass, and observation including external ventricular drainage (EVD). CONCLUSION This study suggests that factors associated with significantly better prognosis include age, clip/coil treatments, and no vermian infarction complication. A treatment algorithm for true PICA aneurysms was supported according to pre-treatment H and K grade, PICA segments, aneurysm morphology, and three types of ischemia linked to the brainstem, cerebellar hemisphere, or vermis.