Prestyloid Parapharyngeal Space Masses

The parapharyngeal space is an inverted pyramid extending from the base of the skull to the hyoid bone. It is bordered laterally by the parotid and masticator spaces, medially by the pharyngeal mucosal space, and posteromedially by the retropharyngeal space.

The tensor-vascular-styloid fascia extends through the parapharyngeal space between the tensor veli palatini muscle and the styloid process. It can be used to divide the parapharyngeal space into pre- and post-styloid compartments. The post-styloid compartment contains the carotid sheath and is also known as the carotid space. The pre-styloid compartment is what most people in the field are actually referring to when they talk about the parapharyngeal space.

The post-styloid compartment (also known as the carotid space) contains the internal carotid artery, internal jugular vein, cranial nerves IX-XII, the cervical sympathetic chain, and the glomus bodies. The pre-styloid compartment (also known simply as the parapharyngeal space) contains fat, lymph nodes, minor salivary glands, nerves (branches of V₃), arteries (internal maxillary and ascending pharyngeal), and veins (pharyngeal venous plexus).

Most commonly, a mass found in the parapharyngeal space has invaded from adjacent spaces:

• Salivary gland masses: Pleomorphic adenoma of the parotid gland most common; diving ranula rare.
• Neurogenic tumors:
• Glomus tumors: Glomus vagale (post-styloid/carotid space),
• Pharyngeal carcinoma: Invasion of the parapharyngeal space seen in 65% of cases at time of diagnosis.
• Tonsillar tumors
• Synovial sarcoma: Fluid levels, hemorrhage, and calcification.
• Lymphadenopathy
• Infection: Tonsillitis, pharyngitis, odontogenic abscess, parotid abscess.
• Chordoma
• Meningioma
• Other: Second branchial cleft cysts (uncommon).

Primary lesions of the prestyloid parapharyngeal space are much less common and can arise from the contents mentioned above:

• Lymphadenopathy: Most common mass in the prestyloid compartment.
• Salivary gland tumors: Pleomorphic adenoma and other minor salivary gland tumors (e.g., mucoepidermoid carcinoma, adenoid cystic carcinoma).
• Neural tumors: Schwannoma.

References

• Shin JH, Lee HK, Kim SY, Choi CG, Suh DC. Imaging of parapharyngeal space lesions: focus on the prestyloid compartment. AJR Am J Roentgenol. 2001 Dec;177(6):1465-70.
• Neuroradiology requisites (2nd ed), pp 721-723.