Carotid space

Dr Jeremy Jones et al.

The carotid space (also known as the post-styloid parapharyngeal space) is one of the seven deep compartments of the head and neck.

The carotid space is a roughly cylindrical space that extends from the skull base through to the aortic arch.  It is circumscribed by all three layers of the deep cervical fascia, forming the carotid sheath 1.

The bifurcation of the common carotid usually occurs at the boundary of the suprahyoid and infrahyoid spaces 1.  

Suprahyoid carotid space:

The suprahyoid portion of the carotid space is often synonymous with the post-styloid compartment of the parapharyngeal space 3.

Ultrasound is good for identifying vascular structures in the lateral neck.  The origin of the internal and external carotid arteries is the main point of sonographic interest as the carotid space superior to this cannot be visualized due to the mastoid process.  

The internal carotid is usually posterolateral to the external carotid however in 5-10% of the population the internal carotid lies medial or anterior or the two vessels may lie within the same frontal plane 1.

The external carotid can be identified from the internal carotid as:

  • it branches within the neck; the first immediate branch is the superior thyroid artery
  • Doppler tracing of vessel flow within the internal carotid is typical of low peripheral resistance (high diastolic peak), whereas the external carotid has high-resistance flow (lower diastolic peak, systolic peak higher than that of the internal carotid) 1
  • CT is often the imaging modality of choice when evaluating for pathology within the carotid space
  • CT is able to identify any benign or malignant tumors within the carotid space and allows for better visualization of any associated bone involvement in comparison to MRI
  • Vascular lesions are best identified with CT angiography 3
  • MRI is useful for identifying between the different types of benign tumors involving the carotid space
  • it provides better soft tissue contrast in comparison to CT and can be useful at elucidating any signs of intramural metastatic nodal invasion of the carotid artery which is a relative contraindication for surgical tumor resection 3

A mass originating from the carotid space will cause anterior displacement of the parapharyngeal space. Lesions can include:

Anatomy: Head and neck
Share article

Article information

rID: 10466
System: Head & Neck
Section: Anatomy
Tag: cases
Synonyms or Alternate Spellings:
  • Carotid sheath
  • post-styloid parapharyngeal space

Support Radiopaedia and see fewer ads

Cases and figures

  • Figure 1: in red on annotated MRI
    Drag here to reorder.
  • Figure 2: in red on annotated MRI
    Drag here to reorder.
  • Updating… Please wait.

     Unable to process the form. Check for errors and try again.

     Thank you for updating your details.