Anatomic Predictors of Occlusion After Flow Diversion for Posterior Inferior Cerebellar Artery Aneurysms: A Single-Center Experience and Systematic Review

BACKGROUND AND OBJECTIVES: Aneurysms involving the posterior inferior cerebellar artery (PICA) are rare and anatomically diverse, encompassing both true PICA and vertebral artery (VA)-PICA junctional lesions. Flow diversion (FD) has emerged as a promising treatment, though evidence remains limited to small series and reports. METHODS: Retrospective review of a prospectively maintained database was performed, identifying all PICA aneurysms treated with FD between 2013 and 2025 at a single US institution. Twenty-two patients (24 aneurysms) were identified. A systematic review and individual patient-level pooled-analysis were conducted, identifying 7 eligible studies (77 patients, 80 aneurysms). RESULTS: Ninety-nine patients (104 aneurysms) were treated in 103 procedures. Most aneurysms were proximal lesions (72.1%) and saccular (65.4%), with a median size of 5.7 mm. Complete occlusion was achieved in 73%, with a median follow-up of 12.6 months. A good functional outcome (modified Rankin Scale 0-2) occurred in 90.1%, with low mortality (2.0%) unrelated to device placement. Distal aneurysms demonstrated significantly higher occlusion than proximal lesions (100.0% vs 62.0%, P < .001). FD landing in the PICA was also associated with significantly higher occlusion than VA (100.0% vs 62.5%, P < .001). One distal aneurysm in the cohort was treated with VA landing, which achieved complete occlusion. Twelve complications occurred in 11 procedures (7 ischemic, 5 hemorrhagic). CONCLUSION: This large cohort provides insights into the safety and efficacy of FD for PICA aneurysms. FD seems highly effective for distal aneurysms, whereas in proximal lesions it should be considered more selectively, after weighing alternative treatments, given the comparatively lower rates of angiographic occlusion.