Optimal Timing of Extracranial-Intracranial Bypass with Microsurgical Trapping for Ruptured Blister Aneurysms of the Internal Carotid Artery

Objective Ruptured blister aneurysms of the internal carotid artery are challenging to treat because of their difficult diagnosis and the fragility of the wall structure. Here, we sought to clarify the efficacy of extracranial-intracranial bypass followed by trapping (bypass/trapping) for ruptured blister aneurysms. Methods A retrospective study identified 45 patients with ruptured blister aneurysms between 1998 and 2017. Our principle was to attempt bypass/trapping as early as possible after diagnosis (early surgery). If early diagnosis was difficult, patients underwent elective surgery in the later stage when aneurysms were detected (elective surgery). Patient characteristics, radiologic findings, clinical course, and outcomes were analyzed. Results Forty-three patients were treated by bypass/trapping. Twenty-eight patients were classified as early surgery and 15 as elective surgery. Two patients experienced fatal rebleeding and did not undergo surgery. All 15 patients in the elective surgery group showed rebleeding and/or aneurysmal growth while awaiting surgery. In the elective surgery group, 10 aneurysms were missed initially by catheter angiography. In the early surgery group, 9 patients were assessed by vessel wall magnetic resonance imaging, which showed circumferential enhancement along the aneurysm wall, most of which was shown as only a small bulge in the angiography. Postoperative rebleeding did not occur in any of the patients. Conclusions Bypass/trapping is effective to prevent rebleeding. Early surgery may be beneficial, because most patients in the elective surgery group showed rebleeding or aneurysmal growth. Vessel wall magnetic resonance imaging is a useful adjunct for early diagnosis and may contribute to prompt early surgery.