前大脳動脈領域における末梢型外傷性破裂脳動脈瘤:閉鎖性頭部外傷に伴う遅発性頭蓋内出血例の検討

Ruptured traumatic aneurysm of the peripheral anterior cerebral artery:study of delayed hemorrhage after closed head injury

I．はじめに

　外傷性頭蓋内脳動脈瘤の発生要因としては，穿通性外傷を主とする直接血管損傷と，閉鎖性外傷による間接損傷があり，特に閉鎖性頭部外傷に伴う外傷性脳動脈瘤は，比較的稀な頭部外傷の合併症とされている．しかも，外傷後ある時期を経てしばしば頭蓋内出血（delayed　hemorrhage）を来たし，また予後も極めて不良であることから^1），頭部外傷の合併症として臨床的にも社会的にも問題となることが多い．

　今回われわれは閉鎖性頭部外傷後，数週間後に突然誘因なく脳内出血を来たし，急激な経過をたどり死亡した3症例の前大脳動脈末梢部領域における外傷性破裂脳動脈瘤を経験したので，それらの臨床経過，CT上の特徴ならびに剖検所見を併せて検討し，本疾患について文献的考察を加え若干の知見を得たので報告する．

We report three cases of ruptured traumatic aneu-rysms of the peripheral anterior cerebral artery after closed head injury.

These cases were all young men with closed head in-jury due to traffic accidents. Consciousness level on admission was coma in all three cases. Case 1 was a 19-year-old man with interhemispheric hematoma on ini-tial CT, then 7 days later his consciousness cleared. However, 14 days later he suddenly lapsed into a deep coma with a severe frontal hemorrhage. Case 2 was a 13-year-old boy. Plain skull films demonstrated a fron-tal depressed fracture, but CT scan showed no bleed-ing. Four days later his consciousness cleared but 11 days after trauma, he lapsed into a deep coma with a frontal hemorrhage. Case 3 was a 22-year-old man. Ini-tial CT showed a slight ventricular hemorrhage. Four-teen days later, his consciousness had almost cleared, but then he lapsed into a deep coma with a large fron-tal hemorrhage 11 weeks after the trauma. These pa-tients all died within a few days after intracranial bleeding. All patients underwent cerebral angiography but none of them showed filling defect. Autopsy was performed and ruptured aneurysms were found on the distal anterior cerebral artery that had no relation to the branch of bifurcation. Histological examination de-monstrated a lack of elastic lamina and media in all of these three cases, so each of them was a victim of so-called false aneurysm.

Twenty reported cases of ruptured traumatic aneu-rysms of the peripheral cerebral artery with delayed hemorrhage after closed head injury were reviewed. Factors in the traumatic aneurysm showed no relation to the duration of disturbed consciousness. Within one month, delayed hemorrhage due to ruptured traumatic aneurysm occurred. None of the delayed hemorrhages involved subarachnoid hemorrhage. Subdural hemato-ma was seen in the distal middle cerebral artery and frontal hemorrhage was found in the distal anterior cerebral artery. We consider that frontal hemorrhage is a predictive finding for the type of delayed hemorrhage due to traumatic aneurysm in the distal anterior cere-bral artery.