Enhancing Mass at the Carotid Bifurcation: Not Always a Carotid Body Tumor

Carotid body tumor (CBT, paraganglioma) is a frequently-encountered enhancing mass at the common carotid artery (CCA) bifurcation. Other enhancing masses occur in this region, and not uncommonly mimic a CBT. An accurate diagnosis has important prognostic and management implications. The correct diagnosis can be made through knowledge of the anatomy of the contents of the carotid sheath and adjacent structures, careful assessment of imaging features of the mass, and supplementation with clinical history. In the presence of a sufficiently large mass, the contents of the carotid sheath will be displaced in a predictable direction based on the origin of the mass. For example, a CBT originates at the notch of the CCA bifurcation and hence displaces the external carotid artery (ECA) and ICA away from each other. Because the vagus nerve is located posteriorly within the carotid sheath between the carotid artery and internal jugular vein (IJV), vagal-origin masses tend to anteriorly and medially displace the CCA (and/or the ECA and ICA together), while laterally displacing the IJV. Most schwannomas originating from the cervical sympathetic chain (SCSC) displace the CCA (and/or ECA and ICA) and the IJV all in the same direction, typically anteriorly or laterally.

Learning Objective: Become familiar with detailed anatomy and relative position of the major structures within and adjacent to the common carotid sheath in the suprahyoid neck, and know the top differential considerations of enhancing masses in the region of the carotid bifurcation, and how to distinguish them on imaging.