Audiology and Vestibular Disorders
Core concepts
Know the types of hearing loss and how each appears on audiometry: conductive loss with an air-bone gap, sensorineural loss with bone and air thresholds equally reduced, and mixed loss. Understand tympanometry types (A, B, C) and their correlates. Be familiar with otoacoustic emissions and auditory brainstem response, particularly for newborn screening and retrocochlear evaluation. For vestibular testing, know the caloric test, videonystagmography, and vestibular evoked myogenic potentials.
Traps
A common trap is interpreting a type B tympanogram as always effusion; it can also occur with a perforation or a probe against the canal wall. Another is assuming a normal audiogram excludes retrocochlear disease; speech discrimination and ABR may still be abnormal. Questions on caloric testing often test that a reduced response indicates a peripheral vestibular lesion on that side. Do not confuse conductive hearing loss from cerumen with sensorineural loss; otoscopy is always the first step.
Worked example
A patient has a pure-tone audiogram showing air thresholds of 40 dB and bone thresholds of 10 dB across frequencies. The 30 dB air-bone gap indicates conductive hearing loss; the next step is otoscopy and tympanometry to identify the cause.