An operated case of aneurysm formation and growth at the site of superficial temporal artery-middle cerebral artery anastomosis: Pathological consideration and a review of the literature

We report the case of a patient with a non-ruptured aneurysm that had developed and expanded at the site of anastomosis of the superficial temporal artery (STA) and middle cerebral artery (MCA).A 58-year-old man had undergone STA-MCA anastomosis and neck clipping of a right MCA aneurysm 8 years ago. Follow-up magnetic resonance imaging (MRI) was performed every year, and the patency of the bypass was confirmed. We first detected the formation of an aneurysm at the site of the anastomosis by using MRI in 2010. We retrospectively evaluated the MRI results and found a bulge at the site of the anastomosis. The size of the aneurysm increased gradually up to 8 mm. The patient underwent neck clipping of the aneurysm. A part of the aneurysm was excised after neck clipping. Histological examination revealed a true aneurysm. The patient's postoperative course was uneventful. Here, we report a rare case of aneurysm formation and growth at the site of anastomosis, with a review of the literature.