Sound-evoked neurogenic responses with short latency: are they of vestibular origin?

Background: In auditory brainstem responses (ABR), recording a large negative deflection with a latency of 3 ms (N3) could be recorded in patients with peripheral profound deafness. It is suggested that N3 might be of vestibular origin. If we can record N3 potentials in subjects with preserved hearing, recording N3 potential will be a new clinical test of the vestibular system. Methods: Twelve healthy volunteers and sixteen patients with vestibular disorders were enrolled. For recording responses, surface electrodes were placed on the ipsilateral mastoid and the vertex. Recording was performed using an auditory evoked potential recording system with a minimixer and a stereo amplifier. Signals were amplified and band-pass-filtered (100-3000 Hz). One thousand hertz short tone bursts were presented to either ear through a headphone with or without white noise (WN) to the ipsilateral to the stimulated ear. The stimulation rate was 10 Hz. The responses to 500 stimuli were averaged. Results: When I kHz STB (95 dBnHL, equivalent to 130 dBSPL) was presented with 100 dBSPL WN, a negative peak with 3 to 4 ms latency (N3) was observed in 23 of the 24 ears of the healthy volunteers. The presence of N3 in the patients was in agreement with the presence of the vestibular evoked myogenic potentials (VEMP), which were also recorded. Conclusion: Using techniques of WN exposure to the stimulated ear, we recorded N3 in healthy subjects. On the basis of results in patients, N3 is likely to be of vestibular origin. (c) 2004 Elsevier B.V. All rights reserved.