Ruptured fusiform aneurysm of the proximal anterior cerebral artery (A1 segment).

A 42-year-old man presented with a ruptured fusiform aneurysm of the proximal anterior cerebral artery (A(1) segment) manifesting as sudden onset of severe headache. Brain computed tomography revealed subarachnoid hemorrhage in the basal cisterns, and left carotid angiography demonstrated a fusiform aneurysm of the left A(1) segment. He underwent surgery via the left pterional approach.