A Case of Anomalous External Carotid Artery

An anomaly of the left external carotid artery (A. carotis externa) of a woman, 59 years old, was found during the dissective operation for the cervical lymph node metastasis caused by tongue and mouth floor carcinoma. When we have tried to ligate the external carotid artery for the neck dissective operation, it was hard to know which was the external carotid artery or the internal carotid artery, because of abnormal distribution. Two branches from common carotid artery were observed : one was anterior and the other was posterior in position. The posterior artery was quite peculiar, however, in its distribution. The artery formed a semicircular loop then turned its direction to upward. Furthermore, a small anastomosing vessel was observed in the lower part of the loop. To decide which is the external carotid artery, 0.4% indigo carmin solution was injected directly into the arteries and observed color changes in the neck and face. Firstly, when the dye solution was injected into the anterior artery, which is usually thought as the external carotid artery, no color changes were observed in the neck and face. On the other hand, the mucous membrane of the oral cavity, the skin of face and the neck region were stained deeply when the dye solution was injected into the posterior artery. Consequently, we found the posterior artery was the external carotid artery and it was anomalous. After the ligation of the posterior artery the neck dissective operation was done successfully. Many reports of the anomalies in cervical arteries have been published. As far as we know, however, the anormaly of the external carotid artery as described in this paper has not been reported.