Ruptured de novo aneurysm arising at a site remote from the anastomosis 14 years after superficial temporal artery-middle cerebral artery bypass: a case report

The long-term outcome of superficial temporal artery (STA)-middle cerebral artery (MCA) bypass is unclear. We report a very rare case of a de novo aneurysm after bypass surgery. A 57-year-old woman who underwent STA-MCA bypass and internal carotid artery aneurysm treatment 14 years earlier developed a subarachnoid hemorrhage and a temporal lobe hematoma on the same side as the anastomosis. Angiography showed excellent patency of the STA bypass and a ruptured de novo saccular aneurysm at a site remote from the anastomosis. Neck clipping and hematoma evacuation were performed on the second day, and postoperative angiography showed complete aneurysmal clipping. The aneurysm was considered to be caused by hemodynamic stress because it was remote from the anastomosis and had developed after a prolonged interval of 14 years; furthermore, the aneurysm projected because of the hemodynamic force of the STA perfusion. This is the first reported case of a de novo MCA aneurysm that developed at a site remote from STA-MCA anastomosis because of hemodynamic force. Therefore, long-term control of blood pressure and repeated imaging examination should be performed to confirm patency and to identify aneurysm formation after STA-MCA bypass.