Postoperative acute ultra-early fish mouthing of a Surpass Evolve flow diverter leading to ischemic complication.

Currently, the Surpass Evolve flow diverter (SE FD) is widely adopted for endovascular treatment of intracranial aneurysms. Although generally safe, acute ultra-early fish mouthing remains an exceptionally rare complication. Following Torche et al.'s 2023 report of the first case, the present case represents the second documented instance. A 66-year-old woman was diagnosed with a left posterior communicating artery aneurysm and a left ophthalmic artery aneurysm. Physical examination revealed no abnormalities. The endovascular treatment (EVT) procedure was performed. After advancing a microcatheter into the left middle cerebral artery, an SE FD with appropriate size was deployed to cover both aneurysms, achieving confirmed complete expansion and optimal wall apposition. Two hours postoperatively, the patient developed aphasia and hemiparesis. Subsequent angiography at 4 hours revealed thrombosis within the SE FD and fish mouthing at the proximal segment. Successful microguidewire traversal through the affected site restored complete FD expansion and wall apposition. Postoperatively, the patient's hemiparesis improved, and her motor aphasia resolved. Magnetic resonance imaging confirmed multiple acute infarctions, while computed tomography demonstrated proper FD expansion. At 3-month follow-up, near-normal functional recovery was observed. This case indicates that SE FD deployment may be complicated by acute ultra-early fish mouthing attributable to post-deployment tension release. Preventive strategies should emphasize appropriate device sizing, adequate landing zone selection, and post-implant tension assessment.