The carotid sheath is a condensation of the deep cervical fascia, or fibrous connective tissue of the neck, which surrounds the great vessels of the neck.
It extends from the base of the skull caudally to the first rib on the sternum. More precisely, it starts bilaterally at the level of the oropharynx on the lateral side of the retropharyngeal space, deep to the sternocleidomastoid muscle. It joins the prevertebral fascia medially and communicates inferiorly with the mediastinum.
In this article, we will discuss the anatomy, relations, and contents of the carotid sheath, as well as some clinical aspects related to this structure.
|Definition||Condensation of the deep cervical fascia that forms the vascular compartment of the neck|
|Location||Lateral to the retropharyngeal space on each side of the neck|
|Contents||Common and internal carotid artery, internal jugular vein and vagus nerve (CN X)|
|Function||Protection of the major neurovascular structures it surrounds|
Fascial layers and relations
The deep cervical fascia of the neck has three layers, listed from superficial to deep. The first is known as the investing layer and surrounds the sternocleidomastoid muscle and the trapezius muscle. The second is called the pretracheal fascia and encloses the visceral region of the neck. Lastly, the third fascial layer is the prevertebral fascia and it surrounds the vertebral region of the neck.
The carotid sheath itself is formed by contributions from all three layers of the deep cervical fascia. This sheath encompasses the vascular compartment of the neck.
Posterior to the carotid sheath is the cervical part of the sympathetic trunk which is embedded in the prevertebral fascia.
The carotid sheath surrounds the following anatomical structures:
- The common carotid artery (CC)
- The internal carotid artery (I See = IC)
- The internal jugular vein (IV)
- The vagus nerve (CN X)
In order to remember this list of the main carotid sheath contents, a popular mnemonic is well worth learning: ‘I See 10CC’s in the IV’ (See list above for correlations).
Pathological conditions that directly affect the carotid sheath are rare. It is much more common to see disorders that affect the contents of the sheath. Vascular disorders, neurological disorders, or lymphatic diseases would affect the sheath and the rest of the contents secondarily.
One scenario however that does involve the sheath is that of an extensive dental infection. The spreading of untreated dental focus can lead to cellulitis within the spaces of the head and neck. Should the fascia of the carotid sheath become involved, the infection could easily spread to the mediastinum and cause mediastinitis or even endocarditis.
Carotid sheath: want to learn more about it?
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