Abstract:
Objective: A systematic literature review and meta-analysis was performed to determine the effect of stimulus type, sternocleidomastoid (SCM) muscle activation method, transducer type and method to control SCM muscle electromyography (EMG) level on response parameter values for 0.1 ms click evoked and 500 Hz tone burst cervical vestibular evoked myogenic potentials (cVEMPs). A description of normative response values was attempted.
Method: An electronic systematic literature review was performed to obtain normative cVEMP response data. Subsequently a meta-analysis was conducted to determine significant effects on cVEMP response parameters and to obtain norms.
The scientific database, Scopus, was used to identify reports containing normative data. Reports were selected based on inclusion and exclusion criteria determined beforehand. Weighted means were calculated and compared to identify significant effects on response parameters and normative data for cVEMP interpretation.
Results: Sixty six reports were included in the systematic review and most prevalent stimulus and recording parameters are identified and tabulated as guidelines for conducting and interpreting cVEMPs in the clinic. Stimulus type had a statistically significant effect on all response parameters (latency P1, latency N1, raw amplitude, corrected amplitude, asymmetry ratio and threshold), where larger latencies were noted for 500 Hz tone burst cVEMPs (TBVs). Stimulus duration was confirmed to produce larger latencies. Larger raw amplitude values were found for TBVs and visual monitoring levels of at least 40 μV is suggested. Larger asymmetry ratios for 0.1 ms click cVEMPs (CVs) were found and upper limits of normality of 14.2% (CVs) and 10.05% (TBVs) are suggested. Higher threshold values were found for CVs and threshold ranges of 89 dB HL (SD 0.88) for CVs and 81.02 (SD 2.03) for TBVs are suggested. SCM muscle activation method, transducer type and method to control SCM muscle EMG level had statistically significant effects on all response parameters, indicating that one method to perform the cVEMP should be chosen and used consistently for accurate interpretation of results.
Conclusions: Optimal stimulus and recording parameters suggested by previous research are confirmed by the current systematic review and meta-analysis and are suggested for clinical use. Response parameter values are influenced by variations in stimulus and recording parameters and normative response values are suggested as guideline for cVEMP interpretation.
