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Pharyngeal recess

The pharyngeal recess, also known as the fossa of Rosenmüller, is a deep mucosal recess located in the lateral wall of the nasopharynx, posterior to the torus tubarius and the opening of the pharyngotympanic (Eustachian) tube. It represents the deepest part of the nasopharyngeal cavity and is an important anatomical landmark in head and neck radiology, endoscopy, and skull base assessment.

It is formed by the lateral pharyngeal wall as it extends posteriorly behind the cartilaginous elevation of the auditory tube. Because of its position at the junction of the nasopharynx, parapharyngeal space, and skull base, it is closely related to several important structures, including the levator veli palatini, longus capitis, and the internal carotid artery laterally within the parapharyngeal region.

Synonyms

  • Fossa of Rosenmüller
  • Lateral pharyngeal recess
  • Rosenmüller fossa

Location and Structure

  • Position: In the lateral wall of the nasopharynx, posterior to the torus tubarius
  • Extent: Recess extends superiorly and posteriorly behind the cartilaginous opening of the Eustachian tube
  • Shape: Slit-like or pouch-like mucosal depression
  • Lining: Covered by nasopharyngeal mucosa
  • Framework: Supported by surrounding pharyngeal soft tissue and adjacent skull base musculature

Relations

  • Anteriorly: Torus tubarius and pharyngeal opening of the auditory tube
  • Posteriorly: Pharyngeal wall and prevertebral soft tissues
  • Medially: Nasopharyngeal airway
  • Laterally: Parapharyngeal space and internal carotid artery at deeper levels
  • Superiorly: Skull base, including the sphenoid and basiocciput region
  • Inferiorly: Soft palate and oropharyngeal continuation
  • Deep relation: Longus capitis muscle and prevertebral fascia

Attachments

  • Mucosal continuity: Continuous with the mucosa of the lateral nasopharyngeal wall
  • Adjacent muscular support: Related to the levator veli palatini and salpingopharyngeus muscles near the torus tubarius
  • Pharyngobasilar fascia: Provides structural support to the nasopharyngeal wall near the recess

Function

  • Nasopharyngeal contour: Contributes to the normal lateral configuration of the nasopharynx
  • Air passage anatomy: Forms part of the lateral boundary of the nasopharyngeal airway
  • Endoscopic landmark: Important reference point during nasopharyngeal examination
  • Anatomic relationship: Helps define the region around the Eustachian tube opening and adjacent pharyngeal musculature

Clinical Significance

  • Radiologic landmark: Essential structure to identify on MRI and CT when assessing the nasopharynx
  • Endoscopic importance: Key landmark in nasopharyngoscopy
  • Skull base relation: Close proximity to deep neck spaces and skull base structures makes it important in cross-sectional imaging
  • Symmetry assessment: Normal bilateral symmetry is an important feature in routine radiologic evaluation

MRI Appearance

T1-weighted images:

  • The pharyngeal recess appears as a small air- or fluid-containing mucosal recess along the lateral wall of the nasopharynx.
  • Air within the recess appears low signal (dark).
  • The mucosal lining is thin and usually not separately conspicuous unless surrounded by bright parapharyngeal fat.
  • Adjacent parapharyngeal fat appears bright, helping outline the lateral nasopharyngeal wall.
  • Nearby muscles such as levator veli palatini and longus capitis show intermediate signal intensity.

T2-weighted images:

  • The recess remains visible as a small dark air-containing space if aerated.
  • Thin mucosa and surrounding soft tissues are better appreciated because adjacent fluid-containing spaces, if present normally in minimal amount, appear brighter.
  • The parapharyngeal fat remains relatively bright, while adjacent muscles appear intermediate-to-dark, darker than fat.
  • The contour of the recess is best appreciated when symmetric on both sides.

STIR:

  • Normal pharyngeal recess is seen as a small low-signal air-containing indentation in the lateral nasopharyngeal wall.
  • Fat suppression reduces the bright signal of surrounding parapharyngeal fat, allowing the mucosal contour and adjacent muscles to stand out more clearly.
  • Adjacent muscles demonstrate intermediate-to-dark signal intensity.
  • The recess is best identified by its smooth outline, lateral location, and symmetry relative to the opposite side.

CT Appearance

Non-Contrast CT:

  • The pharyngeal recess appears as a small air-filled lateral nasopharyngeal recess posterior to the torus tubarius.
  • It is seen as a low-attenuation cleft or pouch against the soft-tissue density of the nasopharyngeal wall.
  • Surrounding muscles and mucosa show soft-tissue attenuation, while adjacent parapharyngeal fat has low attenuation, helping define the lateral margin.
  • The recess is best assessed on axial and coronal images, where it appears as a symmetric lateral indentation of the nasopharyngeal lumen.

Post-Contrast CT:

  • The normal pharyngeal recess maintains the same air-filled or collapsed mucosal contour.
  • The surrounding mucosa may show mild thin enhancement as part of normal nasopharyngeal soft tissue.
  • Adjacent vascular and soft-tissue structures become more distinct, improving delineation of the lateral pharyngeal wall and nearby parapharyngeal space.

MRI image

Pharyngeal recess mri axial image