Otitis media with effusion

Type BReflex: absentDecay: n/aAir–bone gap: Conductive, ~20–40 dB

A flat (type B) trace with a normal equivalent ear-canal volume — the hallmark of fluid loading the middle-ear system.

Audiogram & tympanogram

Audiogram

0204060801001202505001k2k4k8kFrequency (Hz)Hearing level (dB HL)[[[[[[○ air conduction[ bone conduction

Tympanogram

-400-300-200-10001002000.00.51.01.52.02.53.0Ear-canal pressure (daPa)Admittance (mmho)

Reading the two together

Loss type: conductiveMean air-bone gap: 25 dBAir PTA: 32 dB HLDegree: mild

An air-bone gap with normal bone thresholds — the lesion is in the outer or middle ear.

A broadly flat conductive loss — air thresholds elevated by roughly 25–35 dB, bone thresholds normal, a clear air-bone gap at every frequency. The flat type B tympanogram and this flat conductive audiogram are the same fluid-loaded ear seen two ways.

The audiogram tells you how much hearing is lost and where the lesion sits (conductive vs sensorineural); the tympanogram tells you what the middle ear is doing mechanically. Read as a pair, they pin down the diagnosis far more tightly than either does alone.

Teaching point

Type B with NORMAL ECV suggests effusion; type B with LARGE ECV suggests a perforation or a patent ventilation tube. ECV is what disambiguates them.

References

  • Onusko E (2004). Tympanometry. American Family Physician, 70(9), 1713–1720.
  • Fowler CG, Shanks JE (2002). Tympanometry. Handbook of Clinical Audiology (5th ed.), J. Katz (Ed.), pp. 175–204. Lippincott Williams & Wilkins.