The N3 potential and the efferent cochlear pathway in profound sensorineural hearing loss.

OBJECTIVE

This study aimed to evaluate the presence of the N3 potential (acoustically evoked short latency negative response) in profound sensorineural hearing loss, its association with the cervical vestibular evoked myogenic potential and the relationship between both potentials and loss of auditory function.

METHODS

Otological examinations of 66 ears from 50 patients aged from 4 to 36 years were performed, and the vestibular evoked myogenic potential and auditory brainstem response were measured.

RESULTS

The N3 potential was recorded in 36 out of 66 ears (55 per cent) and a vestibular evoked myogenic potential was recorded in 34 (52 per cent). The N3 potential was recorded in 23 out of 34 ears (68 per cent) with a vestibular evoked myogenic potential response and absent in 19 out of 32 ears (59 per cent) without a vestibular evoked myogenic potential response. The presence of an N3 potential was significantly associated with a vestibular evoked myogenic potential response (p = 0.028), but there was no significant difference in the latency or amplitude of the N3 potential in either the presence or absence of a vestibular evoked myogenic potential.

CONCLUSION

The presence of an N3 potential in profound sensorineural hearing loss with good or poor vestibular function can be explained by the contribution of the efferent cochlear pathway through olivocochlear fibres that join the inferior vestibular nerve. This theory is supported by its early latency and reversed polarity, which is masked in normal hearing by auditory brainstem response waves.