eRadiograph Volume 7: Imaging of Oral Cavity | Page 164
Pharyngeal mucosal space
The pharyngeal mucosal space represents the mucosal surface of the oropharynx and
nasopharynx as well as their muscles, bounded by the buccopharyngeal fascia
externally.
Extent and Anatomy
This space lies anteromedial to the parapharyngeal space, anterior to the
retropharyngeal space. Medial to carotid space. It extends from the skull base to the
cricoid cartilage. Superiorly it communicates with the foramen lacerum. This provides
a perineural access for nasopharyngeal carcinomas to extend intracranially.
Nasopharynx
The nasopharynx is the superior most portion of the tubular pharynx located
immediately caudal to the central skull base extending inferiorly to the level of the soft
palate. Below this level lies the oropharynx. Anteriorly the nasopharynx
communicates with the nasal cavity via the choanae. The posterior and posteriolateral
wall of the nasopharynx and oropharynx are contiguous. Posterior to the nasopharynx
lies the clivus. The nasopharynx consists of three layers – an inner mucous lining of
ciliated pseudo stratified epithelum. This mucosa has one protrusion known as torus
tubaris which is the cartilaginous projection of the Eustachian tube. On either side of
this projection are recesses. The anterior recess is for Eustachian tube and the more
posterior recess is the lateral pharyngeal recess known as the fossa or Rosenmuller. The
Eustachian tube drains and aerates the middle ear. The fossa of Rosenmuller is a
common site for the origin of nasopharyngeal CA. The submucosa contains minor
salivary glands, lymphoid tissue of Waldeyer ring (adenoids, palatine and lingual
tonsils) Due to the presence of lymphoid tissue non Hodgkins lymphoma may arise at
this site. Lymphoid tissue has a symmetric striated appearance on T2W and contrast
MRI due to the presence of lymphoid crypts.
The middle layer is a fibrous layer consisting of a tough aponeurosis known as
pharyngobasilar fascia which attaches the superior constrictor muscle to the
undersurface of the clivus. This may be visualized as a thin dark line on T2 W axial
MRI. There is a small hiatus in the pharyngobasilar fascia at its attachment to the skull
base allowing the Eustachian tube and levator veli palatani muscles to pass.
The site of perforation is known as the sinus of morgagni. Since the pharyngobasilar
fascia is pierced at this location disease processes can extend to the skull base via this
hiatus. These two muscles are identified on the lateral nasopharyngeal wall on MRI.
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Pharyngeal Mucosal Space
Contents
The contents of the pharyngeal mucosal space from inner to outer margin are the
pharyngeal mucosa, submucosa, pharyngobasilar fascia, muscles and its covering the
buccopharyngeal fascia.