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Auditory tube

The auditory tube, also known as the Eustachian tube or pharyngotympanic tube, is a narrow canal that connects the middle ear cavity to the nasopharynx. Its main function is to equalize air pressure on both sides of the tympanic membrane and to drain mucus from the middle ear into the nasopharynx. Anatomically, it is an important structure in both otology and head & neck radiology due to its clinical implications in infections and its appearance in imaging studies.

Origin and Insertion

  • Origin:
    Begins at the anterior wall of the middle ear (tympanic cavity)

  • Insertion:
    Ends at the lateral wall of the nasopharynx, at the level of the inferior nasal concha

Structure

  • Approximately 36 mm in length in adults

  • The lateral one-third (posterior) is bony; the medial two-thirds (anterior) is cartilaginous

Nerve Supply

  • Tympanic (middle ear) portion:
    Supplied by the tympanic plexus, mainly branches from the glossopharyngeal nerve (cranial nerve IX)

  • Pharyngeal portion:
    Supplied by the pharyngeal branch of the pterygopalatine ganglion (from the maxillary nerve, V2)

Arterial Supply

  • Pharyngeal branch of the ascending pharyngeal artery (branch of external carotid artery)

  • Artery of the pterygoid canal (from maxillary artery)

  • Middle meningeal artery (contributes minor branches)

Venous Drainage

  • Drains into the pharyngeal venous plexus

  • Some drainage may occur via veins of the middle ear into the pterygoid venous plexus

MRI Appearance

  • T1-weighted images:
    The auditory tube is generally seen as a linear, hypointense (dark) structure relative to surrounding fat and muscles

  • T2-weighted images:
    Appears as a hyperintense (bright) tubular structure when fluid/mucus is present; otherwise, may remain low signal

  • STIR sequences:
    Fluid or edema within the tube will be hyperintense (bright); normal tube may appear relatively dark unless inflamed or filled with fluid

CT Appearance

  • Appears as a soft tissue structure running from the anterior middle ear to the nasopharynx

  • The bony portion is visualized as a narrow canal in the temporal bone

MRI images

Auditory tube mri axial image -img-00000-00000_00001