Nonbifurcating Carotid Artery: A Case Report with a Review of Embryogenesis

BACKGROUND Vascular anomalies of the carotid vessels can be attributed to false embryogenesis. A rare variant called a nonbifurcating carotid artery (NBCA) exists, where typical carotid bifurcation is not recognizable with its typical branches of the external carotid artery (ECA) and internal carotid artery (ICA). This paper describes a case of this anomaly and reviews the embryogenesis of the carotid arteries for explanation. CASE REPORT A 66-year-old man received a routine health examination at our hospital. Initial carotid ultrasound indicated an absence of bifurcation in the right cervical carotid artery, and magnetic resonance imaging of the brain indicated an absence of the proximal cervical segment of the right ICA, with a remnant arterial stump at the expected bifurcation level. No evidence of the carotid bulb was identified. The common carotid artery seemed to continue cranially in the trunk of the ECA, where it exhibited extracranial branches. After distributing these branches, the carotid artery coursed medially at the C2 level, where it ascended into the carotid canal to become the petrosal segment of the ICA. This carotid anomaly was labelled an NBCA. No aberrant intracranial arteries were derived from the NBCA in this case. CONCLUSIONS In this case, the arterial stump was considered a remnant from agenesis of the right ICA. We assumed that the NBCA most likely developed because of false regression of the third embryogenic aortic arch with persistence of the second aortic arch.