Treatment of Unruptured Large and Giant Paraclinoid Aneurysms in Japan at the Time of Flow Diverter Introduction: A Nationwide, Multicenter Survey by the Japanese Society on Surgery for Cerebral Stroke

Background and objectives: Large or giant paraclinoid aneurysms have been treated with various strategies, including clipping, coiling, and parent artery occlusion (PAO). In addition, flow diverters (FDs) have been introduced for the management of these aneurysms. The aim of this study was to examine the management of unruptured large/giant paraclinoid aneurysms in Japan when FDs were being introduced by a nationwide survey.

Methods: A total of 576 unruptured large/giant paraclinoid aneurysms treated in Japan between January 2012 and December 2016 were retrospectively studied.

Results: Half of the large paraclinoid aneurysms were treated by coiling (50.3%), whereas giant aneurysms were occluded mainly by PAO (51.4%). A high nearly complete occlusion rate was achieved with clipping (94.1%), coiling (85.9%), PAO (82.4%), and FDs (77.6%). Coiling had higher risks of recurrence (28.3%) and retreatment (20.3%). Major procedure-related complications were observed in 9.7%. Ischemic complications were common in PAO (9.5%), with cranial nerve symptoms common in clipping (10.9%). All treatment modalities achieved good clinical outcomes (93.5-96.6%). Although not significant, pre-existing visual disturbance improved most frequently by clipping (53.7%), but also worsened most frequently by clipping (24.4%). Consequently, FD achieved a high occlusion rate with minimal complication and retreatment rates.

Conclusion: All treatment modalities offer high rates of complete occlusion and good clinical outcomes. Coiling has the disadvantage of high rates of recurrence and retreatment. Clipping and PAO have the disadvantage of a high rate of major procedure-related complications; however, PAO can provide comparable treatment outcomes even in cases with refractory giant aneurysms. FDs are the optimal choice for the management for large/giant paraclinoid aneurysms due to its safety and efficacy.