Type C tympanogram (marked B) is characterized by a pressure peak shifted to negative values (<−100 daPa), which is the hallmark of eustachian tube dysfunction (ETD). The clinical anchor states: "TYPE C (PEAK SHIFTED TO NEGATIVE PRESSURE <−100 daPa — characteristic of ETD with negative middle ear pressure)." The pathophysiology is impaired opening of the eustachian tube during swallowing/yawning due to inflammation, edema, or structural obstruction (adenoid hypertrophy, nasopharyngeal mass, cleft palate), preventing the tensor veli palatini from equalizing middle ear pressure with the nasopharynx. This generates negative middle ear pressure that retracts the tympanic membrane and causes conductive hearing loss (5–30 dB air-bone gap), exactly as seen in this patient. The anchor text emphasizes: "PATHOGENESIS: Inflammation/edema of the eustachian tube mucosa... prevent the TENSOR VELI PALATINI from opening the tube during swallowing/yawning, generating negative middle ear pressure that retracts the tympanic membrane and impairs sound transmission."
AAO-HNS ETD clinical statement 2019; Schilder Lancet 2015
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