ヘルメットの紐による縊頸が原因と思われる外傷性頸部内頸動脈解離の1例

Traumatic Internal Carotid Artery Dissection Due to Compression by a Helmet Strap

Ⅰ．は じ め に

　外傷性頸動脈解離は比較的稀な病態ではあるが，頸部の過伸展や鈍的外傷により生じることはよく知られている．一方，自動二輪車乗車時のヘルメット着用は頭部外傷に対する予防効果があるとされており^2,3)，わが国でも義務づけられている．ヘルメットの規格はJIS (T8133-1982)により定められており，どのヘルメットも衝撃吸収性や耐貫通性についての条件を満たさなければならない．ヘルメットには頭部顔面全体を覆い下顎骨で固定するタイプのものと，頭部だけを覆い頸部で固定するタイプ(Fig. 1)がある．どちらのタイプも転倒時に頭部を保護する効果があるが，ヘルメットをどう固定するかの規定はなく頸部への影響は考慮されていない．今回われわれは後者のタイプのヘルメットの紐により，転倒時に縊頚を生じて外傷性頸動脈解離を生じたと思われる症例を経験したので報告する．

　It is well known that wearing a helmet can reduce the risk of head injury in a traffic accident. We report a case of traumatic cervical internal carotid artery dissection due to compression by the strap of a helmet after a motorcycle accident. A 21 year-old man fell off his motorcycle and his head was struck at the right parietal region. His helmet prevented head injury,but the helmet strap which was fixed around his neck compressed his cervical internal carotid artery. He lost consciousness and developed left hemiparesis two hours after being admitted to an emergency department. Cerebral angiography revealed dissection of he right cervical internal carotid artery. This lesion was treated successfully by stent placement two months after the accident. The cause of carotid dissection was thought to be compression of his neck by the helmet strap. If the strap of a helmet is fixed around the neck,it can cause carotid artery injury during an accident,so it can be concluded that the strap of a helmet should be fixed firmly at the chin.