鈍的頭部外傷により中大脳動脈M2起始部に仮性動脈瘤を生じた1例

False Aneurysm Formation at the Origin of the M2 Segment of the Middle Cerebral Artery Following a Blunt Head Trauma:A Case Report

Ⅰ．はじめに

　外傷性脳動脈瘤は，中大脳動脈と前大脳動脈の遠位部に好発し，その大部分は損傷動脈に隣接する凝血塊内に内腔を生じる仮性動脈瘤である^1,8)．今回われわれは，外傷性脳動脈瘤の発生部位としては稀な，中大脳動脈近位部（M2起始部）に鈍的頭部外傷により仮性動脈瘤が生じた1例を経験したので報告し，診療上の問題点を考察する．

　A 43-year-old man fell from a 1m-high truck loading platform and sustained an injury in the occiput. On admission, he was alert and neurologically intact. Computed tomography（CT）showed hemorrhage in the right sylvian fissure and parenchyma adjacent to the sphenoid wing. Magnetic resonance angiography detected no abnormalities. The course was uneventful for 11 days. However, on the 12th day, he spontaneously manifested with stupor. CT and CT angiography revealed expansion of the hemorrhage and an aneurysm arising from the origin of the M2 segment of the right middle cerebral artery. After superficial temporal artery to middle cerebral artery bypass, the aneurysm, a reddish pulsatile mass, was removed from the origin of the torn M2 segment, and the laceration was sutured. The histological diagnosis was false aneurysm. He recovered and was discharged 4 months after the trauma. Traumatic cerebral aneurysms are rare in the proximal segment of the middle cerebral artery. However, they should be distinguished from nontraumatic true aneurysms in the same region and treated as false aneurysms, which are major and critical traumatic aneurysms, for favorable outcomes.