Audiology and Vestibular Science
Core rules
Pure tone audiometry separates conductive loss (air-bone gap) from sensorineural loss (no gap). Tympanometry types A, B and C reflect middle-ear pressure and mobility; type B suggests effusion or perforation, and type C suggests negative middle-ear pressure. Otoacoustic emissions reflect outer hair cell function and are useful for screening; they are absent in significant cochlear loss but can be present in retrocochlear disease. Auditory brainstem response assesses the retrocochlear pathway and estimates thresholds in infants. Vestibular testing includes caloric testing for canal paresis, video head impulse testing for the vestibulo-ocular reflex, and VEMP for otolith function. Hearing rehabilitation ranges from hearing aids to cochlear implantation for severe-to-profound sensorineural loss.
Worked example
A 65-year-old reports progressive hearing loss. Audiometry shows high-frequency sensorineural loss with no air-bone gap, and tympanometry is type A. This is presbycusis. Hearing aids are offered, with counseling about communication strategies.
Traps
Not all hearing loss is conductive. Type B tympanometry does not always mean effusion; it can occur with perforation. Present OAEs do not exclude retrocochlear pathology. Do not interpret caloric testing alone as a complete vestibular assessment.