Background: De novo aneurysm formation at the anastomosis site of a superficial temporal artery-middle cerebral artery (STA-MCA) bypass is a rare complication. We report a case of an anastomosis-site aneurysm appearing 3 years after STA–MCA bypass surgery and treated with clipping. Case Description: A man in his forties presented to a nearby hospital with left hemiparesis and dysarthria. Head magnetic resonance imaging and magnetic resonance angiography (MRI/MRA) detected right hemispheric brain infarction due to the right M1 occlusion. After mechanical thrombectomy, the patient recovered without neurological deficits. The patient was admitted to our hospital for follow-up. During follow-up, the right M1 stenosis progressed and thrombosed, with a general decrease in blood flow in the right hemisphere observed on spectroscopy. The patient underwent an STA-MCA bypass 34 months after the first onset of brain infarction. Thirty-three months after the STA-MCA bypass surgery, follow-up MRA at the outpatient clinic showed an aneurysm at the anastomosis site. A retrospective checkup of the previous MRA revealed gradual enlargement of the aneurysm; therefore, surgical intervention was planned to prevent rupture. Intraoperatively, the aneurysm was identified on the STA side. The aneurysmal wall structure was preserved, and normal clipping was performed. The postoperative course was uneventful. There was no recurrence of the aneurysm at the 6 months follow visit to the outpatient clinic. Conclusion: An anastomosis-site aneurysm is a rare complication of STA-MCA bypass. Distinguishing between a true aneurysm and a pseudoaneurysm preoperatively is challenging. A surgical plan that accommodates both types is necessary.
Miyake et al. (Fri,) studied this question.