[Giant serpentine aneurysm followed up for more than 10 years: report of a case and review of the literature].

We report a case of a giant serpentine aneurysm (GSA) located at the left internal carotid artery (ICA) and middle cerebral artery (MCA) treated by ligation of the left ICA with superficial temporal artery-middle cerebral artery (STA-MCA) anastomosis. The aneurysm form changed variously during the follow-up period. A 35-year-old man was admitted with severe headache and convulsion. CT scan demonstrated subarachnoid hemorrhage. Left carotid angiogram demonstrated a giant serpentine aneurysm. Ligation of the ICA with STA-MCA anastomosis was performed because of the difficulty involved in clipping. Right carotid angiogram obtained 5 years later revealed disappearance of the tortuous vascular channel and a new aneurysmal shadow at the left carotid bifurcation. The size of the aneurysmal shadow increased gradually over 10 years. MRI and MR angiography which clearly demonstrated the presence of the aneurysm and the vascular channel simultaneously were considered useful methods for diagnosis of GSA. The authors reviewed previous reports of 19 cases and investigated the mechanism of GSA.