The carotid sheath is a condensation of deep cervical fascia that surrounds the major vasculature of the neck. Contents include:
Common carotid a. (& the proximal internal carotid a.), medially,
Internal jugular v., laterally,
Vagus n. (CN X), posteriorly, and
Deep cervical lymph nodes and the jugular lymphatic trunk.
The carotid sheath is found:
Deep to the SCM m.,
Lateral to the larynx, trachea, pharynx, esophagus, & infrahyoid mm.,
Posterior to the ansa cervicalis (sometimes ansa is embedded within the sheath), and
Anterolateral to the cervical sympathetic trunk.