Retropharyngeal space

The retropharyngeal space(also known as the true retropharyngeal space to distinguish it from the danger space, which is sometimes referred to as part of the retropharyngeal space) is is one of the seven deep compartments of the head and neck. It is a midline space that consists largely of fatty areolar tissue and contains lymph nodes that drain the pharynx, nose and middle ear.

Terminology

Radiologists commonly use the term retropharyngeal space to refer to the space between the visceral compartment (containing aerodigestive structures) and the prevertebral fascia. This level of description matches what is usually discernable on cross-sectional imaging (see Figure 1) ⁴.

Anatomically, this space is subdivided by a thin membrane known as the alar fascia. The alar fascia separates the true retropharyngeal space (anterior) from the prevertebral or danger space⁴.

Gross anatomy

The retropharyngeal space is posterior to the pharynx and oesophagus, and extends from the base of the skull to a variable level between the T1 and T6 vertebral bodies ². The main component of the retropharyngeal space is areolar fat.

Lymph nodes are found in the portion of the retropharyngeal space above the hyoid bone, and these lymph nodes drain the pharynx, nasal cavity, paranasal sinuses and middle ears. These lymph nodes are prominent in children, and atrophy with age ².

Contents

• areolar fat
• lymph nodes (lateral and medial retropharyngeal) only above hyoid 
• small vessels

Relations

The retropharyngeal space is:

• anterior to the danger space
• posterior to the pharyngeal mucosal space
• anteromedial to the carotid space
• posteromedial to the parapharyngeal space

Boundaries

• anterior margin: middle layer of the deep cervical fascia ¹
• posterior margin: alar fascia, which separates the retropharyngeal space from the danger space
• lateral margins: deep layer of the deep cervical fascia ¹
• superior margin: clivus
• inferior margin: the point at which the alar fascia fuses with the middle layer of the deep cervical fascia, typically around the T4 vertebral body ³

Radiographic features

CT/MRI

The retropharyngeal space is a potential space which is directly related to the danger space, the pharyngeal mucosal space, the carotid space and the parapharyngeal space.

The retropharyngeal space appears as a small, roughly rectangular space on axial imaging, wider in the mediolateral dimension and thinner in the anteroposterior dimension. As fatty areolar tissue is the main component of the retropharyngeal space, it has a density consistent with fat on CT and a signal consistent with fat on MRI.

Because the alar fascia is very thin, it is difficult to differentiate the retropharangeal space from the danger space on CT and MRI ³.

Related pathology

• retropharyngeal abscess
• metastatic adenopathy
• lymphoma