A rare case of iatrogenic traumatic intracranial aneurysm which was found on the internal carotid artery 8 months after clipping of the basilar artery aneurysm is reported. A 25-year-old male was admitted with left hemiplegia and conjugate deviation toward the right. Computed tomography and repeat angiographies showed obstruction of the right middle cerebral artery and a fusiform aneurysm of the right internal carotid artery. The clip previously applied on the basilar artery aneurysm appeared touching the fusiform aneurysm. Development of the newly recognized fusiform aneurysm was considered to be due to a chronic pulsatile force on the internal carotid artery.
Only 29 cases, including the authors', of iatrogenic traumatic aneurysms have so far been reported in the literature. The main cause was arterial injury during the first operation. It is emphasized that postoperative angiography is necessary in cases of an injury of the cerebral artery during operation. However, it is very difficult to find an aneurysm such as the one described here.