Air-Conducted Vestibular Evoked Myogenic Potential Testing in Children, Adolescents, and Young Adults: Thresholds, Frequency Tuning, and Effects of Sound Exposure
Authors: Rodriguez Amanda I. , Thomas Megan L. A. , Janky Kristen L. 
Published: June 2018

Objectives:
Pediatric vestibular evaluations incorporate cervical and ocular vestibular evoked myogenic potential (c- and oVEMP, respectively) testing; however, in children, c- and oVEMP thresholds have been minimally investigated and frequency tuning is unknown. Children are also at risk for unsafe sound exposure secondary to VEMP. While it is unknown if VEMP threshold testing leads to cochlear changes, it is possible that this risk increases due to the increased number of trials needed to obtain a threshold. Obtaining VEMP thresholds at various frequencies in children provides further information for pediatric normative VEMP data. Assessing for cochlear changes after VEMP threshold testing would provide information on the safety of threshold VEMP testing in children. The objectives of this study were to (1) characterize c- and oVEMP thresholds in children, adolescents, and young adults with normal hearing using 500 and 750 Hz tone burst (TB) stimuli, (2) compare frequency tuning of 500 and 750 Hz TB, and (3) assess whether cochlear changes exist after VEMP threshold testing. It is hypothesized that children, adolescents, and young adults would not show age-related changes to the vestibular system. Therefore, reliable VEMP thresholds would be seen below maximum acoustical stimulation levels (e.g., <125 dB SPL) and frequency tuning will be similar for 500 and 750 Hz TB stimuli.

Design:
Ten children (age 4–9), 10 adolescents (age 10–19), and 10 young adults (age 20–29) with normal hearing and tympanometry participated. All subjects received c- and oVEMP testing at maximum stimulation and threshold. To address frequency tuning, but not exceed recommended sound exposure allowance, subjects received a 500 Hz TB stimulus in one ear and a 750 Hz TB stimulus in the other ear. Subjects completed tympanometry pre-VEMP, and audiometric threshold testing, distortion product otoacoustic emission testing, and subjective questionnaire pre- and post-VEMP to study the effect of VEMP exposure on cochlear function for each stimulus frequency.

Results:
(1) cVEMP thresholds were determined for both stimulus frequencies for children (500 Hz = 106 dB SPL; 750 Hz = 106 dB SPL), adolescents (500 Hz = 107.5 dB SPL; 750 Hz = 109.5 dB SPL), and young adults (500 Hz = 111.5 dB SPL; 750 Hz = 112 dB SPL). oVEMP thresholds were also obtained in response to both stimulus frequencies for children (500 Hz = 111.1 dB SPL; 750 Hz = 112.2 dB SPL), adolescents (500 Hz = 112.5 dB SPL; 750 Hz = 114.5 dB SPL), and young adults (500 Hz = 116 dB SPL; 750 Hz = 117 dB SPL). Similar thresholds were found between groups except for children who had significantly lower thresholds compared with adults for cVEMP (500 Hz: p = 0.002; 750 Hz: p = 0.004) and oVEMP (500 Hz: p = 0.01; 750 Hz: p = 0.02). In addition, equivalent ear-canal volume and VEMP thresholds were linearly correlated. (2) There was no significant effect of stimulus frequency on VEMP response rates, latencies, peak to peak amplitudes, or thresholds, suggesting similar frequency tuning for 500 and 750 Hz. (3) There were no significant effects of VEMP threshold testing on cochlear function for either stimulus frequency.

Conclusions:
Children, adolescents, and young adults show VEMP thresholds below high stimulation levels and had similar frequency tuning between 500 and 750 Hz. Use of 750 Hz could be regarded as the safer stimuli due to its shorter duration and thus reduced sound exposure. Children with smaller ear-canal volume had present responses at maximum stimulation and lower thresholds, suggesting that VEMP testing could be initiated at lower acoustic levels to minimize sound exposure and optimize testing.