Multicenter experience of pipeline embolization device used in small caliber vessels (< 2 mm) for intracranial aneurysm treatment and mid-term results

Background Flow diversion stents (FDS), particularly the Pipeline Embolization Device (PED), have been widely used for intracranial aneurysm (IA) treatment. However, data on PED deployment in small-caliber parent vessels (< 2 mm) remain limited. This study aimed to evaluate the technical feasibility, safety, and efficacy of PED for IAs arising from small-caliber vessels. Methods This was a multicenter retrospective study enrolling 71 eligible patients with IA located in parent vessels < 2 mm who underwent PED implantation. The primary safety endpoint included procedure-related death, symptomatic stroke, intracranial hemorrhage and asymptomatic in-stent stenosis; the primary efficacy endpoint was complete aneurysm occlusion [O’Kelly-Marotta (OKM) grade D] on follow-up digital subtraction angiography (DSA). Binary logistic regression analyses were used to identify factors associated with complications and delayed IA occlusion. Results The patient age was 55 (47, 59) years, with 37 (52.1%) males. The follow-up duration was 9 (7, 15) months. Postoperative complications included ischemic events (16.9%), hemorrhagic events (4.2%), and asymptomatic in-stent stenosis (12.7%). The 1-year complete occlusion rate was 52%, whereas the long-term occlusion rate gradually increased to 80% with follow-up beyond 12 months. Univariable analysis showed PED length was associated with both delayed IA occlusion [odds ratio (OR) = 0.91, 95% confidence interval (CI) = 0.83–1.00; p = 0.040] and ischemic complications (OR = 1.36, 95% CI = 1.11–1.66; p = 0.003) and also revealed that pre-existing parent vessel stenosis was strongly associated with asymptomatic in-stent stenosis (OR = 13.50, 95% CI = 2.80–65.04; p = 0.001); multivariable analysis confirmed PED length as an independent predictor of ischemic complications (OR = 1.31, 95% CI = 1.06–1.63; p = 0.013). Conclusion PED deployment in small-caliber parent vessels (<2 mm) is technically feasible and clinically viable, with favorable IA occlusion rates and an acceptable safety profile. These findings support the off-label use of PEDs in this challenging cohort, provided rigorous patient selection, optimal procedural planning and close follow-up are implemented.