Carotid sheath !

The carotid sheath is a tube of tissue in the neck holding the carotid artery, the internal jugular vein and the vagus nerve together.

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What it is

A fascial tube around the carotid artery, internal jugular vein and vagus nerve.

What it does

Keeps the three together; surgeons open it in carotid surgery.

Key facts

Where: Skull base to the aortic arch, either side of the trachea and oesophagus
Function: Contains the common and internal carotid arteries, internal jugular vein and vagus nerve; ansa cervicalis on its front

Relations

In front: Sternocleidomastoid and the infrahyoid muscles, with the omohyoid crossing it; the ansa cervicalis on or in its front wall
Medial: Larynx and trachea, pharynx and oesophagus, the thyroid gland and, in the groove between trachea and oesophagus, the recurrent laryngeal nerve
Behind: Prevertebral fascia with the sympathetic trunk, the longus colli and longus capitis, and the cervical transverse processes
Above: At the skull base it continues into the poststyloid part of the parapharyngeal space, where cranial nerves IX to XII run close to it
Contents: Common carotid artery and, higher, internal carotid artery medially; internal jugular vein laterally; vagus nerve behind and between them; deep cervical lymph nodes along the vein

How to find it

Its line runs from the sternoclavicular joint up to midway between the mastoid process and the angle of the mandible, under the anterior border of the sternocleidomastoid. On ultrasound, the round pulsatile carotid lies medial to the larger, compressible internal jugular vein, the standard view for central line placement.

On imaging

Contrast CT shows abscess or fluid tracking along the sheath, internal jugular vein thrombosis as a non-filling vein with an enhancing wall, and spread of cancer to the neck lymph nodes of the jugular chain.

Clinical notes

Carotid endarterectomy and neck exploration open the sheath along the anterior border of the sternocleidomastoid, protecting the vagus nerve behind and the hypoglossal nerve above
Head and neck cancers spread to the deep cervical (jugular chain) nodes around it; radical neck dissection removes the internal jugular vein, the accessory nerve and the sternocleidomastoid with them, modified forms keep one or more
Deep neck abscesses next to the sheath can erode the carotid artery or thrombose the internal jugular vein

Anatomical variants

The internal jugular vein usually lies lateral to the carotid, but in some people it overlaps the artery from the front, and turning the head increases the overlap; this is why central lines are placed under ultrasound with the head kept near neutral
The right internal jugular vein is usually larger than the left

Memory aid

Vein outside, artery inside, vagus at the back between them.

Test yourself

Think of the answer, then tap the question to see it.

What are the contents of the carotid sheath and how are they arranged?

Common (then internal) carotid artery medially, internal jugular vein laterally, vagus nerve behind and between them, with deep cervical lymph nodes along the vein.

Which fascial layers form the carotid sheath?

All three layers of the deep cervical fascia: investing, pretracheal and prevertebral.

What is Lemierre syndrome?

After a sore throat, septic thrombophlebitis of the internal jugular vein (classically Fusobacterium necrophorum) with septic emboli to the lungs.

On ultrasound for central line placement, how are the carotid artery and internal jugular vein told apart in the carotid sheath?

The round, pulsatile carotid lies medial; the larger, compressible internal jugular vein lies lateral.

Which nerve lies on or in the front wall of the carotid sheath?

The ansa cervicalis.

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Educational information, not medical advice. For any symptom, see a health professional.

Its names

Official Latin (TA2): vagina carotidis TA2 2214
Official Spanish (DeCS): Vaina carotídea DeCS D005205
English (TA2): Carotid sheath

Sources: Terminologia Anatomica (TA2); DeCS; Anatomy, Head and Neck: Carotid Sheath.

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Representative model, for educational purposes only.