Parotid Space Overview

Summary Thoughts: Parotid Space

The parotid space (PS) lies in the lateral suprahyoid neck in the cheek anterior to the external auditory canal (EAC). The main content of the PS is the parotid gland, but many other critical structures, such as the facial nerve (CNVII), external carotid branches, and intraparotid lymph nodes, also lie within the boundaries of this space.

The PS is traditionally divided into superficial and deep compartments . The true dividing line between these compartments is the CNVII, but the nerve is not visible on routine imaging, so an imaginary line between the stylomastoid foramen and the lateral margin of the retromandibular vein serves as a radiologic surrogate.

The deep PS compartment lies anterior to the styloid process and lateral to the parapharyngeal fat. The deep compartment was previously called the " prestyloid parapharyngeal space " to emphasize these anatomic relationships. Recalling the older name may help when determining the site of origin of a parapharyngeal mass; a mass arising anterior to the styloid process, displacing the parapharyngeal fat medially, is parotid in origin.

In the setting of a PS mass, the key findings are benign vs. aggressive margins, unifocal vs. multifocal, and homogeneity vs. heterogeneity. Potential involvement of CNVII must be carefully sought.

The main goal of imaging a parotid mass is not to provide a precise diagnosis (since this is often difficult). Instead, the main goal is to guide the next step in the work-up . For example, would a fine-needle aspiration be useful? Does the patient need an oncologic excision with neck dissection?

Key findings in PS inflammation include calculi, ductal dilatation, and the number of glands affected.