Otoacoustic emission and auditory efferent function testing in patients with sensori-neural hearing loss

To examine the role of otoacoustic emissions and auditory efferent system function in evaluating auditory functional status in both normal and diseased conditions.

Spontaneous and transient evoked otoacoustic emissions and efferent function in terms of contralateral white noise induced transient evoked otoacoustic emission suppressions were tested and cross compared in 32 normal ears, 24 ears with cochlear hearing loss and 16 ears with retrocochlear hearing loss.

Transient evoked otoacoustic emission amplitude and contralateral suppression, spontaneous otoacoustic emission incidence, peaks and frequency range were significantly reduced in cochlear hearing loss while in retrocochlear hearing loss transient evoked otoacoustic emission and spontaneous otoacoustic emission levels were significantly higher than in cochlear hearing loss group and showed no suppression.

Contralateral acoustic stimulation induced transient evoked otoacoustic emission suppression as an index of efferent function is clinically feasible. Combined otoacoustic emission and efferent tests are of great significance in evaluating cochlea status and auditory central mechanisms. Auditory efferent function is weakened in cochlear lesions and severely damaged in retrocochlear lesions.