[Giant fusiform aneurysm with dissection in the middle cerebral artery: a case report].

: A rare case of a giant fusiform aneurysm with dissection in the middle cerebral artery is reported. A 37-year-old man was referred to our hospital for severe headache and left retrobulbar pain. MRI and angiography showed a giant aneurysm in the temporal branch(M 2) of the left middle cerebral artery. We supposed that dissection had occurred from a giant fusiform aneurysm in the middle cerebral artery judging from presentation, MRI findings, angiography findings, and operative findings. Giant fusiform aneurysms in the middle cerebral artery(MCA) are uncommon cerebral aneurysms. The surgical approach or endovascular treatment to giant fusiform aneurysms in the MCA is technically difficult, so some patients are treated conservativery. However they have a poor natural history that differs from that of typical saccular aneurysms. And they have character of weakness in the internal elastic lamina, and therefore have the potential to dissect. We suggest that appropriate therapy including conservative therapy and surgical techniques is necessary for giant fusiform aneurysms even if they are found incidentally.