Anatomy

The nasopharynx is a hollow passageway, lined by mucosa, that serves to connect the nasal cavity to the oropharynx (Figure 7-1). It is bounded anteriorly by the posterior nasal choanae and nasal septum. The floor is formed by the superior surface of the soft palate and is in communication with the oropharynx at the level of the uvula. The posterior wall of the nasopharynx lies anterior to the first 2 cervical vertebrae, pre-vertebral and buccopharyngeal fascia, superior pharyngeal constrictor muscles and the pharyngeal aponeurosis. The roof is formed by the basisphenoid and basioccipital bones of the skull base. The lateral walls lie medial to the maxillopha-ryngeal space, pterygoid plates, and parapharyngeal space. The eustachian tube orifices enter the nasopharynx in the lateral walls and each is surrounded by a cartilaginous protuberance called the torus tubarius. A recess behind the torus tubarius, Rosenmuller's fossa, is the most common location for cancers to arise.

Cancers of the nasopharynx have multiple routes for local spread. Tumors commonly extend into the nasal cavity, oropharynx, parapharyngeal space and skull base. The sphenoid sinus is more commonly invaded than the ethmoid or maxillary sinuses. The orbit, cervical vertebrae and pterygoid structures may be involved in advanced disease. Invasion of the clivus occurs frequently. Tumors may extend through the foramen lacerum, ovale, or spinosum to the cavernous sinus, potentially involving cranial nerves (CN) II to VI. Less commonly, tumors may invade the cranium through the carotid canal, jugular foramen, or hypoglossal canal.

Branches of the external carotid artery provide blood supply to the nasopharynx while venous drainage is through the pharyngeal plexus, to the internal jugular vein. Nerve supply is provided by branches of cranial nerves V2, IX, and X, as well as sympathetic nerves. The nasopharynx has a rich

Figure 7-1. Mid-sagittal section of the nasopharynx and surrounding structures. Inset demonstrating the relationship of the nasopharynx to foramina of the skull base.

lymphatic network with multiple pathways for drainage. The first echelon lymph nodes are in the parapharyngeal and retropharyngeal space. The highest paired lymph nodes in this chain are named the nodes of Rouviere. Drainage to the jugular chain may occur by way of the parapharyngeal lymph nodes or by direct channels. A separate direct pathway leads to lymph nodes of the spinal accessory chain, in the posterior triangle. Further drainage may occur to the contralateral neck and down the cervical chains to the supraclavicular lymph nodes.

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