Congenital arterial anomaly in the middle ear presenting as a glomus tumor.

A case of congenital agenesis of the cervical internal carotid artery with rerouting via the inferior tympanic artery and the embryonic hyoid artery to the horizontal internal carotid artery is presented. At otoscopy the anomaly simulated a glomus tumor. CT scan, by demonstration of the absence of the vertical portion of the carotid canal, the enlargement of the inferior tympanic canaliculus, and the soft tissue mass within the middle ear in continuity with the horizontal internal carotid artery, diagnosed the anomaly very accurately.