Carotid Artery (CA)

Abstract

There are two common carotid arteries. The left common (LC) carotid artery arises from the aortic arch and the right common (RC) carotid artery from the brachiocephalic trunk. The common carotid arteries run cranially in the carotid space, surrounded by the three layers of the deep cervical fascia, called the carotid sheet. Approximately at the level of the hyoid bone, usually between the C4 and C6 vertebral bodies, each common carotid artery divides into the internal carotid artery (ICA) and external carotid artery (ECA). Cases of a higher bifurcation, up to the first cervical vertebra (Lie 1968), or lower, in the upper thoracic levels (Vitek and Reaves 1973), have been reported. The carotid sheet is a well-defined structure below the carotid bifurcation, though it is incomplete or absent at the level of the oral-nasal pharynx (Harnsberger 1995). The infrahyoid segment of the carotid space contains the common carotid artery, which is located in the so-called anterior triangle, defined by the sternocleidomastoid muscle, laterally and posteriorly, and by the superior belly of the omohyoid and the posterior belly of the digastric muscle, inferiorly and superiorly. The suprahyoid segment of the carotid space contains the ICA, more laterally and posteriorly the jugular vein, cranial nerves (IX, X, XI, and XII), the sympathetic plexus, and the chain of the lymph nodes (Fig. 2.1). Near the skull base, the borders of the carotid space are as follows: laterally, the parotid space; anteriorly and medially, the parapharyngeal and retropharyngeal spaces, respectively; posteriorly, the perivertebral space (Fig. 2.1c).