[Traumatic anterior cerebral artery aneurysm difficult to distinguish from congenital cerebral aneurysm: case report].

We report the case of a 29-year-old woman in whom a saccular aneurysm of the distal anterior cerebral artery developed following head trauma due to a car accident. She was semicomatose on admission but had no lateralizing motor signs. Reflexes were symmetrical, with bilateral extensor toe sign. X-ray of the skull showed no fracture but CT scans demonstrated a large frontal hematoma and interhemispheric bleeding. Initial cerebral angiography performed within 12 hours of trauma showed a small protrusion on the pericallosal portion of the left pericallosal artery with no branching point nearby. Angiography was repeated on the 9th day after admission and confirmed the presence of a saccular aneurysm of the pericallosal artery, which had been visible as a small protrusion on the initial angiogram. Traumatic aneurysm was suspected and successful neck clipping of the aneurysm was performed on the 14th day. Preoperative CT and angiographic findings could not rule out a congenital aneurysm but the histological study of the specimen confirmed that it was a traumatic false aneurysm. We discussed the diagnosis and the etiology of posttraumatic aneurysm.