Cervical vestibular-evoked myogenic potentials (cVEMPs): Differentiation of inter-neck EMG symmetry between children and adults

A cervical Vestibular-Evoked Myogenic Potential (cVEMP) is one of the few objective vestibular diagnostic tests available for pediatric populations. This test evaluates the functionality of the saccule end organ through an inhibitory reflex on the sternocleidomastoid (SCM) muscle that inhibits the level of electromyographic (EMG) activity (Wiener-Vacher, 2013). Because the saccule response is measured as an inhibition of EMG in the SCM, it is imperative that the SCM have a tonic contraction prior to eliciting the response and that the contraction of the SCM is equal on the right and left sides. It is generally accepted that young, healthy adults can generate equal amounts of EMG on both their right and left sides, but these results have not been replicated in young children. There is very little cVEMP data for children under five years of age, and EMG, EMG monitoring, and amplitude normalization has not been studied in this age group. As a result, this study sought to compare generated EMG levels between pediatric and adult populations, to determine if EMG monitoring and amplitude normalization would significantly reduce interaural amplitude asymmetry (IAA) in either group, and to assess any developmental effects on cVEMP parameters. During testing, participants were placed in a seated, head-turned, position. An iPad was used to incentivize children to turn their head for a better SCM muscle contraction; adults were simply asked to turn their heads. Our findings showed that children were able to produce similar EMG values as adults in the same position, and that they were able to generate equal amounts of EMG on both their right and left sides. While we did not find statistical evidence for the use of EMG monitoring and amplitude normalization when performing a cVEMP, there were individual cases within our data that showed using these techniques could have clinical relevance