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Pharyngeal opening of auditory tube

The pharyngeal opening of the auditory tube (Eustachian tube) is the nasopharyngeal orifice of the tube that connects the middle ear cavity to the nasopharynx. It is located on the lateral wall of the nasopharynx, posterior to the nasal cavity, and plays a crucial role in ventilation, pressure equalization, and drainage of the middle ear.

The opening is surrounded by a prominent mucosal elevation known as the torus tubarius, formed by the underlying cartilage of the auditory tube. Adjacent folds and recesses, including the salpingopalatine fold, salpingopharyngeal fold, and pharyngeal recess (fossa of Rosenmüller), are important anatomical landmarks in both imaging and endoscopic evaluation.

Synonyms

  • Pharyngeal orifice of auditory tube
  • Nasopharyngeal opening of Eustachian tube
  • Tubal opening

Location and Structure

  • Position: Lateral wall of the nasopharynx, at the level of the inferior nasal concha posteriorly
  • Shape: Slit-like or oval opening with mucosal elevation
  • Torus tubarius: Prominent ridge formed by cartilaginous support
  • Pharyngeal recess: Deep space posterior to the torus tubarius
  • Mucosal lining: Respiratory epithelium with ciliated cells aiding drainage
  • Orientation: Directed laterally, posteriorly, and slightly superiorly toward the middle ear

Relations

  • Anteriorly: Posterior nasal cavity and choana
  • Posteriorly: Pharyngeal recess (fossa of Rosenmüller)
  • Superiorly: Base of skull (sphenoid bone and clivus region)
  • Inferiorly: Soft palate and oropharyngeal inlet
  • Laterally: Cartilaginous auditory tube and parapharyngeal space
  • Medially: Nasopharyngeal air column

Attachments

  • Cartilage of auditory tube: Forms the structural framework of the opening
  • Salpingopalatine fold: Contains fibers of tensor veli palatini muscle
  • Salpingopharyngeal fold: Contains salpingopharyngeus muscle
  • Pharyngobasilar fascia: Supports the mucosal wall
  • Muscular relations: Tensor veli palatini and levator veli palatini assist in opening the tube

Function

  • Ventilation: Equalizes air pressure between the middle ear and external environment
  • Drainage: Facilitates clearance of middle ear secretions into the nasopharynx
  • Protection: Prevents reflux of nasopharyngeal secretions into the middle ear
  • Dynamic opening: Opens during swallowing and yawning via muscular action

Clinical Significance

  • Eustachian tube dysfunction: Leads to pressure imbalance and middle ear disease
  • Otitis media: Often related to impaired drainage through this opening
  • Adenoid hypertrophy: May obstruct the pharyngeal opening
  • Nasopharyngeal carcinoma: Frequently arises in the pharyngeal recess near this opening
  • Endoscopic landmark: Critical in nasopharyngeal examination and surgical navigation

MRI Appearance

T1-weighted images:

  • Nasopharyngeal air space: Low signal (dark)
  • Mucosa: Intermediate signal lining the opening
  • Torus tubarius cartilage: Intermediate-to-low signal
  • Adjacent fat planes (parapharyngeal space): Bright, providing contrast
  • Muscles (levator and tensor veli palatini): Intermediate signal intensity

T2-weighted images:

  • Air: Dark signal
  • Mucosa: Intermediate-to-bright signal depending on hydration
  • Cartilage: Intermediate signal
  • Adjacent soft tissues: Muscles appear intermediate, slightly darker than mucosa
  • Nasopharyngeal secretions (if present physiologically): Bright signal

STIR:

  • Normal mucosa and cartilage: Intermediate-to-dark signal
  • Muscles: Intermediate signal
  • Fat: Suppressed (dark), improving visualization of surrounding structures
  • Nasopharyngeal lumen: Dark due to air

CT Appearance

Non-Contrast CT:

  • Nasopharyngeal airway: Low attenuation (black)
  • Pharyngeal opening: Seen as a slit-like air-filled communication on lateral wall
  • Torus tubarius: Soft tissue prominence along lateral nasopharyngeal wall
  • Cartilage: Not distinctly visualized but inferred by contour
  • Adjacent bones: Skull base structures (sphenoid, clivus) well defined
  • Parapharyngeal fat: Low attenuation, outlining soft tissue structures

Post-Contrast CT (standard):

  • Mucosa: Mild uniform enhancement
  • Muscles: Moderate enhancement (levator and tensor veli palatini)
  • Torus tubarius region: Enhancing soft tissue ridge
  • Adjacent soft tissues: Clear delineation of nasopharyngeal wall and surrounding spaces 

MRI images

Pharyngeal opening of auditory tube mri axial image