Parapharyngeal space

The parapharyngeal space, also known as the prestyloid parapharyngeal space, is one of the deep compartments of the head and neck. It consists largely of fat and other connective tissue.

Gross anatomy

The parapharyngeal space is shaped like a pyramid, inverted with its base at the skull base, with its apex inferiorly pointing to the greater cornu of the hyoid bone ².

Contents

• fat (main component)
• vessels
  • ​​internal maxillary artery, depending on its course
  • ascending pharyngeal artery, depending on its course
  • pterygoid venous plexus, in its portion surrounded by fat (the rest is within the masticator space)
• nerve
  • small branch of the mandibular division of the trigeminal nerve (cranial nerve V3) supplying the tensor veli palatini muscle
• salivary tissue
  • minor or ectopic salivary gland/rests
  • retromandibular portion of the deep lobe of parotid gland, in some definitions ⁴

Lymph nodes and muscle are not included in the radiological definition of the parapharyngeal space.

Boundaries

The parapharyngeal space has complex fascial margins occupying the space between the muscles of mastication and the muscles of deglutition²:

• superior margin: base of skull
• inferior margin: greater cornu of the hyoid bone
• medial margin: middle (pretracheal) layer of the deep cervical fascia
• lateral margin: investing fascia of the deep cervical fascia covering the deep lobe of the parotid
• anterior margin: investing fascia of the deep cervical fascia covering the medial pterygoid muscle
• posterior margin: prevertebral layer of the deep cervical fascia

Relations

• posteromedial to the masticator space, particularly medial pterygoid muscle
• anteromedial to the parotid space
• posterolateral to the pharyngeal mucosal space
• anterolateral to the prevertebral space, retropharyngeal space, and danger space
• anterior to the carotid (poststyloid parapharyngeal) space
• overlaps with the infratemporal fossa ⁴

Radiographic features

CT/MRI

The parapharyngeal space is crucial to the understanding of the deeps spaces of the neck, as it has direct relations with all but one of the other six deep compartments of the head and neck (the exception being the danger space, which is separated from the parapharyngeal space by the retropharyngeal space). 

The parapharyngeal space appears as a small triangular space (on axial imaging) with density/signal consistent with fat.  

Knowledge about the displacement patterns of fat within the parapharyngeal space will aid in the localization of lesions within adjacent spaces. A lesion arising in the: 

• masticator space displaces the parapharyngeal fat posteromedially
• parotid space displaces the parapharyngeal fat anteromedially
• pharyngeal mucosal space displaces the parapharyngeal fat posterolaterally
• retropharyngeal space, danger space, and prevertebral space displace the parapharyngeal fat anterolaterally
• carotid (poststyloid parapharyngeal) space displaces the parapharyngeal fat anteriorly

Related pathology

A lesion arising in the parapharyngeal space will displace the carotid space posteriorly and/or is completely surrounded by parapharyngeal space fat. Lesions include:

• salivary gland tumors (most common ³), most commonly pleomorphic adenoma
• neurogenic tumors, most commonly trigeminal schwannoma
• lipoma
• parapharyngeal abscess or phlegmon