Clinical comparison of flow diversion and microsurgery for retreatment of intracranial aneurysms.

[BACKGROUND] The goal of aneurysm retreatment is effective, durable obliteration. Flow diversion (FD) and microsurgical clipping generally represent two aneurysm treatment options with high obliteration rates. However, their relative efficacy in aneurysm retreatment has been infrequently evaluated. We thus sought to compare the radiographic and neurological outcomes of microsurgery to FD for retreatment of intracranial aneurysms (IA)s.

[METHOD] A single institution database was reviewed to identify patients undergoing retreatment for IAs over a two-year period via either FD or microsurgery. Obliteration rates and neurological outcomes were compared between the two retreatment modalities and across subgroups. Impact of retreatment modality was adjusted via multivariate logistic regression analyses.

[RESULTS] Sixty-seven retreatments were identified, 60 % via microsurgery and 40 % via FD. Microsurgery was more commonly performed for anterior communicating artery (Acomm) aneurysms (p = 0.04), residual size < 10 mm (p = 0.02), and aneurysms initially treated endovascularly (p = 0.02). FD was more commonly performed for ICA aneurysms (p = 0.01) and residual size > 10 mm (p = 0.02). Angiographic obliteration rates and neurological outcome were similar overall between the two retreatment modalities at a median follow-up of 26 months. Raymond I obliteration after 12-month follow-up was 94.9 % after microsurgery and 95.2 % after FD (p = 1.00). Good neurological outcome (mRS 0-2) was similar between FD and microsurgery (92.6 % versus 90 %, p = 1.00). Comparable outcomes were observed across several subgroups, including previously ruptured aneurysms and aneurysms requiring retreatment within 6 months. Compared with a 10 % major complication rate after microsurgery, no major events occurred after FD (p = 0.14).

[CONCLUSION] FD is an appropriate endovascular option for IA retreatment, with comparable efficacy and neurological outcome to microsurgery at 2-year follow-up. Longer-term follow-up will be critical to more accurately determine therapeutic efficacy.