Tympanometry of an adult with ear fullness and autophony shows a clear peak with normal height, but at a peak pressure of minus 280 daPa. This tracing represents:
- A Type A, normal middle ear function
- B Type C, significant negative middle ear pressure ✓
- C Type B, middle ear effusion
- D Type Ad, disarticulated ossicular chain
Correct answer: B. Type C, significant negative middle ear pressure
Explanation
Compliance is normal and a definite peak is present, so this is a Type A configuration, but the peak occurs at markedly negative canal pressure. A Type B tympanogram reflects negative middle ear pressure, usually from Eustachian tube obstruction, which sucks the drum inward; peaks beyond about minus 100 to minus 150 daPa are considered significant. Type C is a flat curve without any peak, and Type Ad combines a normal pressure peak with excessively high compliance.
Reference: Dhingra, Diseases of Ear, Nose and Throat, 8th ed.
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Written and medically reviewed by the StethoPrep medical team.