頭蓋外内頸動脈解離性動脈瘤の一剖検例

Autopsied Case of an Extracranial Internal Carotid Artery Dissecting Aneurysm

I．はじめに

　頭蓋外内頸動脈動脈瘤は文献上まとまった報告は少なく，比較的稀な疾患と考えられる^{5,9,11,13，14,18）}．成因としては，感染性，解離性，動脈硬化性，外傷性，線維筋異形成などの血管変性，頸部の外科手術後，頸部の放射線照射後等が挙げられている^{9-11,13-15,18）}．最近は画像診断の進歩により偶然発見される動脈瘤が増加し動脈瘤の発生病態も明らかになりつつあるが^10），非外傷性の頭蓋外内頸動脈解離性動脈瘤（extracranial internal caro-tid artery dissecting aneurysm：EICADA）の成因をはじめとして不明な点も多い．今回われわれは病理所見上動脈硬化が成因と考えられたEICA-DAの一剖検例を経験したので，病理組織所見を中心に文献的考察を加えて報告する．

An autopsy case of extracranial internal carotid artery (ICA) dissecting aneurysm due to atherosclerosis was reported.

A 74-year-old man was admitted to our hospital with the chief complaints of hoarseness and a pulsatile mass below the left mandibular angle. Neurological examination showed no obvious deficits except left re-current laryngeal nerve palsy. Angiography revealed narrowing of the original segment of left ICA with dissection and aneurysmal dilation at the level of C3 vertebra. Seven days after admission, the patient had a sudden onset of consciousness disturbance. The second angiography showed no obvious changes com-pared with the first findings except slight narrowing in the distal portion above the aneurysmal dilation. The possible mechanism was thought to be recanalization following transient occlusion of the left ICA caused by extension of dissection or intracranial embolism due to a thrombus within the aneurysm. He was managed conservatively, but unfortunately he died of pneumonia. Macroscopic autopsy showed that the aneurysm was fusiform. Histologically, it demonstrated dissection of the hematoma between the media and adventitia layer. Hemorrhage in the atheromatous plaque with disruption of the elastic lamina were observed along with severe degenerative changes of the intima, media and, in part, adventitia layer due to atherosclerosis. In addition, a dissecting aneurysm of the right iliac artery and severe arterioscler-osis were observed in the systemic arteries. On the basis of these findings, the dissecting aneurysm pre-sumably developed after disruption of a weak portion of the atherosclerotic wall, where intraplaque hemor-rhage occured earlier. We suggest that atherosclerosis be regarded as one of the pathogenic factors capable of causing dissecting aneurysm of the extracranial ICA in elderly patients.