Department of Research, Boys Town National Research Hospital, Omaha, Nebraska, USA.
Ear Hear. 2018 Mar/Apr;39(2):269-277. doi: 10.1097/AUD.0000000000000484.
Vestibular evoked myogenic potential (VEMP) testing is increasingly utilized in pediatric vestibular evaluations due to its diagnostic capability to identify otolith dysfunction and feasibility of testing. However, there is evidence demonstrating that the high-intensity stimulation level required to elicit a reliable VEMP response causes acoustic trauma in adults. Despite utility of VEMP testing in children, similar findings are unknown. It is hypothesized that increased sound exposure may exist in children because differences in ear-canal volume (ECV) compared with adults, and the effect of stimulus parameters (e.g., signal duration and intensity) will alter exposure levels delivered to a child's ear. The objectives of this study are to (1) measure peak to peak equivalent sound pressure levels (peSPL) in children with normal hearing (CNH) and young adults with normal hearing (ANH) using high-intensity VEMP stimuli, (2) determine the effect of ECV on peSPL and calculate a safe exposure level for VEMP, and (3) assess whether cochlear changes exist after VEMP exposure.
This was a 2-phase approach. Fifteen CNH and 12 ANH participated in phase I. Equivalent ECV was measured. In 1 ear, peSPL was recorded for 5 seconds at 105 to 125 dB SPL, in 5-dB increments for 500- and 750-Hz tone bursts. Recorded peSPL values (accounting for stimulus duration) were then used to calculate safe sound energy exposure values for VEMP testing using the 132-dB recommended energy allowance from the 2003 European Union Guidelines. Fifteen CNH and 10 ANH received cervical and ocular VEMP testing in 1 ear in phase II. Subjects completed tympanometry, pre- and postaudiometric threshold testing, distortion product otoacoustic emissions, and questionnaire addressing subjective otologic symptoms to study the effect of VEMP exposure on cochlear function.
(1) In response to high-intensity stimulation levels (e.g., 125 dB SPL), CNH had significantly higher peSPL measurements and smaller ECVs compared with ANH. (2) A significant linear relationship between equivalent ECV (as measured by diagnostic tympanometry) and peSPL exists and has an effect on total sound energy exposure level; based on data from phase I, 120 dB SPL was determined to be an acoustically safe stimulation level for testing in children. (3) Using calculated safe stimulation level for VEMP testing, there were no significant effect of VEMP exposure on cochlear function (as measured by audiometric thresholds, distortion product otoacoustic emission amplitude levels, or subjective symptoms) in CNH and ANH.
peSPL sound recordings in children's ears are significantly higher (~3 dB) than that in adults in response to high-intensity VEMP stimuli that are commonly practiced. Equivalent ECV contributes to peSPL delivered to the ear during VEMP testing and should be considered to determine safe acoustic VEMP stimulus parameters; children with smaller ECVs are at risk for unsafe sound exposure during routine VEMP testing, and stimuli should not exceed 120 dB SPL. Using 120 dB SPL stimulus level for children during VEMP testing yields no change to cochlear function and reliable VEMP responses.
由于前庭诱发肌源性电位（VEMP）测试具有识别耳石功能障碍的诊断能力和测试可行性，因此在儿科前庭评估中越来越多地使用该测试。然而，有证据表明，为了获得可靠的 VEMP 反应而需要的高强度刺激水平会在成人中造成听力损伤。尽管 VEMP 测试在儿童中具有实用性，但类似的发现尚不清楚。据推测，由于与成人相比，儿童的耳道容积（ECV）存在差异，以及刺激参数（例如，信号持续时间和强度）的影响，因此可能会对儿童耳朵的暴露水平产生影响。本研究的目的是：（1）使用高强度 VEMP 刺激物测量正常听力（CNH）的儿童和正常听力的年轻成人（ANH）的峰间等效声压级（peSPL）；（2）确定 ECV 对 peSPL 的影响，并计算 VEMP 的安全暴露水平；（3）评估 VEMP 暴露后耳蜗是否发生变化。
这是一个两阶段的方法。第 I 阶段有 15 名 CNH 和 12 名 ANH 参加。测量等效 ECV。在一只耳朵中，以 5-dB 增量记录 500-750-Hz 啁啾声的 105 至 125 dB SPL 的 5 秒 peSPL。然后使用记录的 peSPL 值（考虑到刺激持续时间），根据 2003 年欧盟指南中推荐的 132dB 能量津贴，计算出用于 VEMP 测试的安全声音能量暴露值。第 I 阶段有 15 名 CNH 和 10 名 ANH 在一只耳朵中接受了颈性和眼性 VEMP 测试。受测者完成了鼓室图测试、测试前后听力阈值测试、畸变产物耳声发射以及问卷调查，以研究 VEMP 暴露对耳蜗功能的影响。
（1）在高强度刺激水平（例如 125 dB SPL）下，与 ANH 相比，CNH 的 peSPL 测量值明显更高，ECV 更小。（2）等效 ECV（通过诊断性鼓室图测量）与 peSPL 之间存在显著的线性关系，并且对总声能暴露水平有影响；基于第 I 阶段的数据，确定 120 dB SPL 是用于儿童测试的安全刺激水平。（3）使用计算出的 VEMP 测试安全刺激水平，在 CNH 和 ANH 中，VEMP 暴露对耳蜗功能（通过听力阈值、畸变产物耳声发射幅度水平或主观症状测量）没有显著影响。
与成人相比，儿童对常用于 VEMP 测试的高强度 VEMP 刺激的反应中，peSPL 记录的声音要高约 3dB。等效 ECV 有助于 VEMP 测试期间传递到耳朵的声音，并应考虑确定安全的声学 VEMP 刺激参数；ECV 较小的儿童在常规 VEMP 测试中存在不安全声音暴露的风险，刺激不应超过 120 dB SPL。在 VEMP 测试中对儿童使用 120 dB SPL 刺激水平不会对耳蜗功能产生影响，并可获得可靠的 VEMP 反应。
