Audiology, Department of Linguistics, Macquarie University.
Department of Neurological Sciences, Prince of Wales Hospital, Randwick.
Otol Neurotol. 2021 Dec 1;42(10):e1592-e1599. doi: 10.1097/MAO.0000000000003316.
We compared two means of mitigating the effect of sternocleidomastoid (SCM) contraction strength on the cervical vestibular evoked myogenic potential (cVEMP): contraction matching and amplitude normalization.
SCM muscle contraction strength affects the amplitude of the cVEMP which can impact measures of inter-side asymmetry and diagnostic outcomes.
In 19 normal subjects, we investigated the effect of muscle contraction variation within a cVEMP recording. We then compared cVEMP recordings on the right and left sides with matched and unmatched muscle contraction strength using raw amplitudes and amplitude ratios (i.e., normalized amplitudes).
Contraction variability had significant effects on small sections of a cVEMP recording, but there was no significant effect on overall cVEMP amplitude, suggesting that the cVEMP is relatively unaffected by variable effort during a recording. Matching the contraction across the two sides (d = 0.53, p = 0.016) and amplitude normalization (d = 0.43, p = 0.004) both significantly reduced inter-side asymmetry, but normalization had no additional benefit once the sides were matched (interaction effect, p = 0.019). cVEMPs recorded with matched contractions had the smallest range of asymmetry values.
The study shows that controlling the background contraction during a cVEMP recording, either by using similar contractions for each trial or by normalizing the amplitude, reduces cVEMP asymmetry and can prevent incorrect results in the minority of subjects who make asymmetric muscle contractions.
我们比较了两种减轻胸锁乳突肌（SCM）收缩强度对颈前庭诱发肌源性电位（cVEMP）影响的方法：收缩匹配和幅度归一化。
SCM 肌肉收缩强度会影响 cVEMP 的幅度，从而影响双侧不对称性的测量和诊断结果。
在 19 名正常受试者中，我们研究了在 cVEMP 记录中肌肉收缩变化的影响。然后，我们使用原始幅度和幅度比（即归一化幅度）比较了右侧和左侧的 cVEMP 记录，以匹配和不匹配肌肉收缩强度。
收缩变异性对 cVEMP 记录的小部分有显著影响，但对总体 cVEMP 幅度没有显著影响，这表明在记录过程中，cVEMP 相对不受可变努力的影响。两侧收缩匹配（d=0.53，p=0.016）和幅度归一化（d=0.43，p=0.004）均显著降低了双侧不对称性，但一旦两侧匹配，归一化就没有额外的益处（交互效应，p=0.019）。匹配收缩记录的 cVEMPs 具有最小的不对称值范围。
该研究表明，通过在 cVEMP 记录中控制背景收缩，无论是通过为每个试验使用相似的收缩还是通过幅度归一化，都可以减少 cVEMP 的不对称性，并防止少数不对称肌肉收缩的受试者出现错误结果。
