Eustachian tube dysfunction (ETD) is considered by many to be the underlying cause of chronic otomastoiditis, although both the exact pathogenesis and role of ETD in chronic middle ear infections is unclear.
ETD is estimated to be present in ~1% of the adult population.
It has been demonstrated that equalization of middle ear pressure, and flow of contrast out of the middle ear is poor in a high percentage of patients with chronic otomastoiditis, even though only ~33% demonstrate occlusion of the Eustachian tube or tubal filling defects (e.g. polyps). Dysfunction of the tensor veli palatini muscle has also been implicated. In patients with cleft palate ~50% demonstrate conductive hearing loss as a result of abnormal muscular function.
Failure to equalize middle ear pressure can lead to negative pressure causing tympanic membrane retraction, mucoperiosteal thickening and even acquired cholesteatomas due to the aforementioned retraction of the tympanic membrane.
The converse has also be postulated; failure of the Eustachian tube to close normally (known as patulous tube syndrome) during strong inspiration (i.e. 'sniff') transmits negative pressure to the middle ear and tympanic membrane with the same sequelae as above.
CT petrous temporal bone (high resolution)
May show opacification of the middle ear cavity +/- adjacent mastoid air-cells due to secretory otitis and there usually no ossicular chain erosion or disruption unless there is a superimposed infection - inflammation 4.
May show the presence of an associated mass lesion.
Treatment and prognosis
Tympanoplasty may be required to restore normal function.
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