Head and Neck Imaging

Carotid space

1. Anatomy

space extending from the base of the skull to the aortic arch, completely encircled by a fascial sheath composed of the three layers of the deep cervical fascia (see cervical fascias). The carotid space contains a number of important neurovascular structures, such as the carotid artery and internal jugular vein and the vagal nerve. In the suprahyoid neck, the carotid space is considered by some authors to belong to the retrostyloid part of the parapharyngeal space.

A common variant in the carotid space is an asymmetry of the internal jugular veins; most often the right vein is larger than the left one. Sometimes such a large vein can be felt in the neck as a soft mass.

2. Pathology

  • The most frequent pathology concerns the lymph nodes present in this space (see lymph nodes of the neck organization and lymphadenopathy head and neck).

  • A schwannoma head and neck may be seen, usually arising from the vagal nerve (Fig.1); these lesions typically grow between the common or internal carotid artery (usually displaced anteromedially) and the internal jugular vein (displaced posterolaterally). Rarely, neurofibroma may be seen in the carotid space.

  • A glomus vagale tumour also spreads the internal carotid artery and internal jugular vein apart but displays the characteristics of a glomus tumour. A glomus jugulare tumour may grow downwards into the carotid space.

  • The carotid space may be invaded by a pharyngeal squamous cell carcinoma head and neck, which may spread further craniocaudally along the neurovascular structures.

  • An occlusion of the internal carotid artery or an internal jugular vein thrombosis are sometimes encountered.

  • MRI is an accurate technique for diagnosing dissection of the internal carotid artery (see internal carotid artery dissection).

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    Fig.1

    T2-weighted (a) and gadolinium-enhanced T1-weighted (b) spin-echo images, showing a nonhomogeneous mass in the carotid space, displacing the internal carotid artery (arrowhead) anteromedially and the internal jugular vein (arrow) posterolaterally. Vagal schwannoma.
    Carotid space, Fig.1 (a)
    Carotid space, Fig.1 (b)