Delayed Rupture Presenting as Direct Carotid-Cavernous Fistula after Flow Diversion for a Cavernous Internal Carotid Artery Aneurysm with Enlarging Blebs: A Case Report.

OBJECTIVE: This study aimed to report a case of delayed rupture presenting as a direct carotid-cavernous fistula following flow diversion for a cavernous internal carotid artery aneurysm with enlarging blebs. CASE PRESENTATION: An 82-year-old woman with a progressively enlarging right cavernous internal carotid artery aneurysm and 2 enlarging blebs underwent flow diversion using a Pipeline embolization device (Medtronic, Irvine, CA, USA) under dual antiplatelet therapy. On postoperative day 1, diffusion-weighted MRI revealed a small right corona radiata infarction causing mild disorientation and left hemiparesis; the patient remained ambulatory. On postoperative day 6, she developed pulsatile tinnitus without headache. 3D-CTA and cerebral angiography revealed rupture of a neck-adjacent bleb, with the formation of a new direct carotid-cavernous fistula (Barrow type A). Because a balloon occlusion test performed prior to flow-diverter treatment demonstrated intolerance to parent artery occlusion, parent artery sacrifice was considered infeasible. A microcatheter was advanced transvenously into the cavernous sinus and subsequently into the aneurysm sac through the rupture site and coil embolization was performed, resulting in a marked reduction in shunt flow with disappearance of cortical venous reflux. The patient was transferred to a convalescent rehabilitation hospital for rehabilitation of left hemiparesis and was discharged home 3 months after onset with a modified Rankin Scale (mRS) score of 1. CONCLUSION: Even extradural cavernous internal carotid artery aneurysms may undergo delayed rupture following flow-diverter placement. In aneurysms with enlarging blebs, careful early surveillance is warranted, and transvenous intra-aneurysmal embolization may be an effective alternative when parent artery occlusion is not feasible.