Approaches to the Parapharyngeal Space

Abstract

The parapharyngeal space (PPS) is a potential space between the skull base above and the hyoid bone below. It has an inverted teepee shape. Its borders include the nasopharynx and oropharynx medially, the masticator space anterolaterally, the deep lobe of the parotid gland posterolaterally, and the retropharyngeal space posteromedially. The PPS can harbor tumors and infectious processes, but both infectious processes and neoplasms are rare. Tumors can originate in the PPS or can invade the space from neighboring areas. Pleomorphic adenoma is the most common benign tumor of the PPS, followed by schwannomas and paragangliomas. Malignant tumors arising in the PPS can invade the intracranial compartment, maxilla, mandible, temporomandibular joint, orbit, or skin. Hematogenous or lymphatic spread can also occur, as well as perineural invasion along cranial nerves. Perineural invasion is common in adenoid cystic carcinoma and is the pathway to the intracranial space, so imaging studies should be directed toward the foramen ovale, foramen rotundum, cavernous sinus, orbital apex, trigeminal ganglion, and dura. In addition, the radiological evaluation of any patient with suspected malignancy must include the neck, to evaluate for lymph node metastasis. Symptoms include change in voice, trismus, mass in the upper neck, cranial nerve deficits, serous otitis media (due to Eustachian tube obstruction), and obstructive sleep apnea. Standard surgical approaches to the PPS include the transcervical approach, the transparotid-transcervical approach, the transmandibular approach, the endoscopic transnasal approach, the transoral robotic surgery, and the infratemporal fossa approach. The anatomical extent of the tumor, its histologic type (benign or malignant), and the patient’s medical history (previous surgeries or radiation treatment) determine the surgical approach. This chapter describes the common surgical approaches to the PPS.