PARAPHARYNGEAL AND RETROPHARYNGEAL SPACES: NORMAL ANATOMY AND CASE DISCUSSION

Abstract

<h3>Background</h3> An appreciation of the complex anatomy of potential spaces and fascial planes of the neck is vital to understanding lesions and their potential complications. The involvement of the parapharyngeal space (PPS) and the retropharyngeal space (RPS) poses significant diagnostic and therapeutic problems. The PPS extends from the skull base to the superior cornu of the hyoid bone, connecting posteromedially with the retropharyngeal space, inferiorly with the submandibular space, and laterally with the masticator space. The carotid sheath courses through this space into the chest. RPS lies between the visceral division of the middle layer of the deep cervical fascia around the pharyngeal constrictors and the alar division of the deep layer of deep cervical fascia posteriorly. PPS contains mainly fat and the pterygoid venous plexus, whereas the RPS contains retropharyngeal lymphatics. <h3>Clinical and Radiologic Findings</h3> We outline the normal anatomy of the PPS and the RPS on images derived from cone beam computed tomography (CBCT), medical computed tomography (CT), and magnetic resonance imaging (MRI) data sets. Then we present unique case studies exhibiting pharyngeal retention cyst in the tonsil, Tornwaldt cyst in the nasopharynx, nasopharyngeal carcinoma with invasion of the PPS, incidental retropharyngeal internal carotid arteries that can be mistaken for a pseudomass, large goiter with retropharyngeal extension, retropharyngeal air in barotrauma, and retropharyngeal lymphadenopathy occupying the PPS. <h3>Discussion/Conclusions</h3> Displacement of the PPS laterally implicates a lesion in the pharyngeal mucosa posteriorly, the masticator space anteriorly, and the carotid space anterolaterally. Medial displacement implies that the lesion resides in the parotid space. Infection may enter the retropharyngeal airspace directly, as with traumatic perforations of the posterior pharyngeal wall or esophagus, or indirectly, from the parapharyngeal space A fundamental skill set is required for the diagnosis and management of these potentially life-threatening illnesses.