Introduction
This topic covers the region around the pharynx: the parapharyngeal space at its side, the retropharyngeal space behind it, and the fasciae that separate them from the surrounding regions. It links the infratemporal region, the neck and the oral and nasal cavities, and infections and tumours often spread along it.
The pharynx and its fascial covering
The pharynx is a muscular tube, about 12 to 14 cm long, that runs from the base of the skull to the level of the cricoid cartilage. It is divided into the nasopharynx, oropharynx and laryngopharynx. Its wall is formed by the superior, middle and inferior constrictor muscles, which overlap, and by the longitudinal muscles stylopharyngeus, salpingopharyngeus and palatopharyngeus. The pharyngobasilar fascia lies between the mucosa and the constrictors, and the buccopharyngeal fascia covers the outer surface of the constrictors.
The parapharyngeal space
The parapharyngeal space is a fat-filled space lateral to the pharynx, extending from the base of the skull down to the greater horn of the hyoid bone. Its boundaries are:
- Medially: the pharyngobasilar fascia and the superior constrictor, with the tonsillar fossa.
- Laterally: the medial pterygoid muscle, the ramus of the mandible and the deep lobe of the parotid gland.
- Anteriorly: the pterygomandibular raphe, which separates it from the buccal region.
- Posteriorly: the prevertebral fascia and the prevertebral muscles.
The styloid process and the muscles attached to it (stylohyoid, styloglossus and stylopharyngeus) with their fascia divide the space into an anterior, prestyloid compartment and a posterior, retrostyloid compartment.