Tailoring endovascular strategy to posterior inferior cerebellar artery segment anatomy: Avoiding brainstem infarction in dissecting pseudoaneurysms.

BackgroundDissecting pseudoaneurysms of the posterior inferior cerebellar artery (PICA) are rare, high-risk lesions with outcomes heavily influenced by anatomical location. This study evaluates the relationship between PICA segmental anatomy, endovascular treatment strategy, and clinical outcomes.MethodsWe retrospectively analyzed 21 patients with dissecting PICA aneurysms treated endovascularly between 2013 and 2025. Aneurysms were anatomically classified by segment (P1-P5); P3 was further subdivided into P3A (proximal to the PICA loop) and P3B (distal to the loop). Primary outcome was discharge modified Rankin Scale (mRS ≤ 2; classified as favorable). Secondary outcomes included ischemic stroke and segment-specific treatment trends.ResultsOf 21 patients, 16 (76%) were female and 13 (62%) were White; mean age was 57.3 ± 15.5 years. Most aneurysms were small (<7 mm,  = 16, 76%), ruptured ( = 17, 81%), and located in proximal segments (P1-P3,  = 14, 67%). Hypertension was present in 11 (52%) and intraventricular hemorrhage (IVH) in 12 (57%). Treatments included coiling ( = 10, 48%), Onyx embolization ( = 5, 24%), flow diversion ( = 2, 10%), and adjunctive techniques ( = 3, 14%). Deconstructive strategies were used in 14 (67%). Favorable outcome (mRS ≤ 2) was achieved in 15 (71%). Clinically silent cerebellar strokes occurred in 9 (43%); no brainstem infarctions were seen. IVH was significantly associated with poor outcome ( = 0.043). All P3A cases ( = 3) had favorable outcomes, while 2 of 4 P3B cases (50%) were unfavorable.ConclusionsPICA segment anatomy predicts treatment safety. Reconstructive strategies are preferred for proximal lesions (P1-P3A); deconstructive methods are safe and effective beyond the PICA loop (P3B-P5).