Persistent hypoglossal artery arising from the external carotid artery diagnosed by MR angiography

Abstract

Extremely rarely, a persistent hypoglossal artery arises from the external carotid artery; only three cases have been reported in the English-language literature. The purpose of this paper is to report a case of this variation diagnosed by magnetic resonance (MR) angiography. A 75-year-old man with sudden-onset right hemiparesis and dysarthria underwent emergency cerebral MR imaging and cerebral MR angiography that included the cervical carotid bifurcation. A 1.5-T scanner was used and MR angiographic images were obtained using the standard three-dimensional time-of-flight technique. On MR angiography, an anomalous artery arose from the proximal right external carotid artery, ascended just like the ascending pharyngeal artery, entered the hypoglossal canal (anterior condyloid foramen), and finally connected with the terminal segment of the right vertebral artery (VA). The proximal right VA was not visible, probably due to hypoplasia. We present the first case of this anomaly diagnosed using MR angiography, and we propose the term "type 2 persistent hypoglossal artery" to describe this condition.