Auditory Temporal Resolution After Exposure to the Acoustic Stimuli Used for Vestibular-Evoked Myogenic Potential: A Preliminary Investigation.

OBJECTIVES

Vestibular-evoked myogenic potentials (VEMP) are elicited using high-intensity signals, often 125 dB peSPL or higher. Evidence from human experiments documenting cochlear hypofunction after VEMP test using stimulus intensities of 133 and 130 dB peSPL is concerning. However, recent reports found 125 dB peSPL safe as it caused no significant change in pure-tone thresholds and otoacoustic emissions. Nonetheless, previous studies have reported that loud sounds can affect several auditory processes, including temporal resolution, despite no significant change in pure-tone thresholds or otoacoustic emissions. However, all the studies to date investigating the effects of VEMP-eliciting stimuli have used pure-tone audiometry and/or otoacoustic emission. The possibility of a post-VEMP change in temporal resolution remains unexplored. Therefore, the present study aimed to investigate the potential effects of VEMP-eliciting stimuli on temporal resolution by evaluating gap detection thresholds (GDT).

DESIGN

In an experimental time-series research design, 30 young adults underwent a 500-Hz tone burst evoked cervical and ocular VEMP testing. They also underwent GDT testing just before the VEMP test and at 4 other time points (5 min, 1 hr, 24 hr, and 2 wk) after it. In cases of a persistently higher GDT than the baseline, the participants were re-evaluated after 2 mo.

RESULTS

A significant change in GDT at the post-VEMP measurement points of 5 min and 2 wk ( p < 0.008, α -corrected, Wilcoxon signed-rank test after Friedman test) was observed. Nearly 23% of VEMP ears had significantly worse GDT at 5 min after exposure; however, everyone recovered to the pre-exposure GDT level by the end of the experimental paradigm.

CONCLUSIONS

Acoustic stimuli presented at an intensity of 125 dB peSPL to elicit VEMP can potentially influence the auditory system temporarily. Nevertheless, comparing the potential benefits of the VEMP test to its temporary ill effects weighs the odds in favor of the VEMP test, especially given that cVEMP is the only possible assessment tool for the saccular function.