Audiology and Vestibular Medicine: Test Interpretation
Scope
Audiology and vestibular medicine tests pure-tone audiometry, tympanometry, acoustic reflexes, auditory brainstem response, otoacoustic emissions, vestibular testing, and hearing rehabilitation. The board expects you to interpret patterns and identify urgent asymmetry.
Core rules
- Pure-tone average uses 500, 1000, and 2000 Hz. An air-bone gap indicates conductive loss; bone-conduction loss indicates sensorineural loss. Speech discrimination adds prognostic information.
- Tympanometry: type A normal, type B flat from effusion, type C negative pressure from eustachian tube dysfunction. Acoustic reflexes assess the middle-ear and neural pathway.
- Auditory brainstem response wave V and interpeak latencies help assess retrocochlear disease and infant hearing. Otoacoustic emissions reflect outer hair cell function.
- Vestibular tests: video head impulse test assesses the vestibulo-ocular reflex; caloric testing assesses low-frequency function; cervical and ocular vestibular evoked myogenic potentials assess otolith pathways.
- Asymmetric sensorineural hearing loss requires MRI of the internal auditory canal to exclude vestibular schwannoma.
- Noise-induced hearing loss shows a 4-kHz notch; presbycusis is high-frequency and bilateral.
Worked example
A 55-year-old has asymmetric sensorineural hearing loss, poor speech discrimination, and tinnitus. MRI shows a small vestibular schwannoma. Treatment options include observation, radiosurgery, and microsurgery; a hearing aid alone does not address the retrocochlear diagnosis.
Traps
Ignoring asymmetric sensorineural loss; calling a type B tympanogram otosclerosis; failing to mask during audiometry; relying on caloric testing alone; and missing central causes of vertigo.