Aetiology
Eustachian tube dysfunction (ETD) may be caused by intrinsic swelling of the tube orifice or within the lumen, owing to inflammation (e.g., due to allergy) or infection. It may also result from extrinsic compression of the tube by adenoid hypertrophy, tumour, or trauma.[3][4]
ETD also may be related to a failure of the muscles associated with Eustachian tube opening, including:
Tensor veli palatini (a dilator of the Eustachian tube)
Levator veli palatini
Salpingopharyngeus (which opens the Eustachian tube with deglutition)
Tensor tympani.
Pathophysiology
Infectious and inflammatory conditions associated with ETD include viral upper respiratory infection, allergic rhinitis, and chronic rhinosinusitis.[5][6]
Allergy has been implicated in the pathogenesis of ETD through the following mechanisms:[7]
Oedema and congestion of the nasal mucosa
Impaired mucociliary clearance, which leaves secretions overlying the tubal orifice, causing intraluminal inflammation
Hypersecretion of mucus-producing glands in the orifice, causing obstruction.
Similarly, chronic rhinosinusitis has been implicated in the pathogenesis of ETD through impaired mucociliary secretions depositing over the orifice, and through oedema associated with chronic inflammation in the region of the torus tubarius.[8][9]
Direct obstruction of the Eustachian tube may be due to adenoid hypertrophy, or to a tumour in the nasopharynx or infratemporal fossa. Another, well-documented anatomical cause of ETD is cleft palate. The possible mechanisms for this include a more horizontal Eustachian tube and abnormal attachments or inadequate functioning of the muscles involved with tube opening.[3]
Other potential factors that have been implicated in ETD as causing impedance of mucociliary clearance include: tobacco smoke, gastro-oesophageal reflux, and radiation exposure.[10][11][12]
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