An unexpected variation of occipital and ascending pharyngeal arteries: clinical implications

The eight typical External Carotid Artery (ECA) branches are the superior thyroid artery, ascending pharyngeal artery, lingual artery, facial artery, occipital artery, posterior auricular artery, maxillary artery, and superficial temporal artery. The Internal Carotid Artery (ICA) has no branches in the cervical region before entering the carotid canal. We identified a variant of the Occipital Artery (OA) and Ascending Pharyngeal Artery (APA) originating in the cervical portion of the ICA and wish to explore the clinical implications this variation may have.

Between August and December 2023, 28 formaldehyde donors were dissected in the anatomy course for first-year medical and physician assistant students at the Creighton University School of Medicine, Phoenix campus.

In one donor, dissection of the right common carotid artery (CCA) revealed a variation of the ECA branches. Two branches were found on the proximal portion of the ICA. After tracing the branches cranially, we identified these as the OA and APA. These two arteries typically originate from the ECA. The bifurcation angle was observed to be nearly 180 degrees. This variation was only observed on the right side.

As the prevalence of this variation has only been described in one study, reporting at 0.14%, documentation and education of this anatomy aids surgeons and interventional radiologists in head and neck procedures. Exploring the paths of these ectopic arteries promotes informed decision making and risk stratification for carotid endarterectomy, arterial embolization, bypass procedures, and arterial harvesting. Furthermore, performing thorough imaging such as CT angiograms on patients preoperatively provides better foresight to minimize complications.