Visceral space

The visceral space or compartment is a deep compartment of the head and neck that contains the thyroid gland, larynx, trachea, upper esophagus, hypopharynx and, in some definitions, oropharynx and nasopharynx.

Terminology

Of the deep head and neck compartments, the visceral space has the most controversial terminology.

The main difference is the superior limit of the visceral space. Authors differ as to whether the visceral fascia, part of the middle layer of the deep cervical fascia, extends superiorly only to the hyoid bone or to the skull base ¹. As such, some authors restrict the visceral space to the infrahyoid neck ², including in this article, while other authorities subsume the entire pharyngeal mucosal space, including nasopharynx and oropharynx, as a subcomponent or synonym of the visceral space ^1,3,4.

A second difference is the posterior limit of the visceral space. Some authorities divide the visceral space into an anterior "pretracheal space" and a posterior "retrovisceral space" ³, the latter of which is synonymous with the retropharyngeal space superiorly and retroesophageal space inferiorly. In this definition, the entire visceral space is posteriorly delimited by the alar fascia, which is part of the deep layer of the deep cervical fascia, rather than by the visceral fascia. The rationale is that there is a free communication between these two spaces at the level between the thyroid cartilage and the inferior thyroid artery. The term "pretracheal" is confusing, however, as the space contains the trachea itself. Thus, most authors consider the visceral space separately from the retropharyngeal space ^1,2,4, including in this article.

A few authors have restricted the term to the potential space between the visceral fascia and the enclosed viscera, rather than inclusiveexclusive of the organs and mucosa, but this view is not widespread ^1,3.

Because of this confusion, rather than citing the visceral space in radiology reporting and communications with surgeons, a more practical alternative is localizing pathology to their more traditional anatomic descriptors such as "pharynx", "larynx", "trachea", "esophagus", or "thyroid" and their anatomic subsites.

Gross anatomy

The visceral space extends from the hyoid bone superiorly to the superior mediastinum (level of aortic arch / T4), and is surrounded by the middle layers of the deep cervical fascia. 

Contents

• thyroid gland
• parathyroid glands
• oesophagus
• larynx
• hypopharynx
• trachea
• recurrent laryngeal nerve
• lymph nodes (level VI)

Related pathology

Due to the contents of the visceral space, a wide range of conditions can occur in the visceral space such as: 

• thyroid cancer
• parathyroid adenoma
• head and neck squamous cell carcinoma