Tympanogram Type Cs — Eustachian Dysfunction with Effusion
medium
ear ENT
A 7-year-old child presents with a 6-week history of aural fullness, mild otalgia, and conductive hearing loss of 15 dB on audiometry. Otoscopy reveals a retracted tympanic membrane with a prominent malleus handle. Tympanometry is performed and shows a peak shifted to negative pressure (-150 daPa) with reduced compliance compared to normal. The tympanogram is classified as the type marked **A** in the diagram. Which of the following best describes the pathophysiology underlying this tympanographic finding?
A. Normal eustachian tube function with intact tensor veli palatini and levator veli palatini contraction during swallowing
B. Eustachian tube dysfunction with secondary mucosal thickening and early serous effusion, but not yet sufficient to flatten the tympanogram completely
C. Patulous eustachian tube with abnormally high compliance and positive middle ear pressure
D. Complete obstruction of the eustachian tube lumen with established middle ear effusion and absent tympanic membrane compliance
Explanation
Why Option 1 is correct
Type Cs tympanogram (marked A in the diagram) shows a peak shifted to negative pressure (typically -100 to -400 daPa) with reduced peak compliance — a shallow peak at negative pressure. This intermediate pattern reflects Eustachian tube dysfunction (ETD) with secondary mucosal thickening or early serous effusion, but the effusion is not yet established enough to produce the flat, absent-compliance pattern of Type B. The negative pressure develops because the eustachian tube fails to equalize middle ear and atmospheric pressure during swallowing and yawning (due to impaired tensor veli palatini and levator veli palatini function or obstruction). This sustained negative pressure causes mucosal transudation and early fluid accumulation. The reduced compliance indicates the middle ear is becoming stiffer due to early fluid, but the tympanogram retains a discernible peak — distinguishing Type Cs from Type B (flat, no peak). [AAO-HNS OME Guideline 2016; Dhingra ENT 7e]
Why each distractor is wrong
Option 2: This describes Type B tympanogram (established OME with complete effusion), not Type Cs. Type B shows a flat tympanogram with absent or severely reduced compliance and no identifiable peak. Type Cs still has a measurable peak at negative pressure, indicating the effusion is early and not yet fully established.
Option 3: This describes a patulous eustachian tube, which would show abnormally high compliance and positive or normal middle ear pressure on tympanometry. Type Cs shows negative pressure, not positive, and reduced (not increased) compliance. Patulous ETD is rare and presents with autophony of breathing and voice, not the clinical picture here.
Option 4: Normal eustachian tube function would produce a Type A tympanogram (marked D in the diagram) with a peak at normal pressure (0 daPa) and normal compliance. The presence of negative pressure and reduced compliance explicitly indicates dysfunction, not normal function.
High-YieldNEET PG
Type Cs = ETD + early effusion (negative pressure + shallow peak); Type B = established OME (flat, no peak); Type C = pure ETD (negative pressure + normal compliance). In pediatric cases, adenoid hypertrophy is the most common mechanical cause; in adults with unilateral persistent OME, always scope the nasopharynx to rule out nasopharyngeal carcinoma.
AAO-HNS OME Guideline 2016; Dhingra ENT 7e
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