Vestibular evoked myogenic potentials: Test-retest reliability and normative values obtained with a feedback method for the sternocleidomastoid muscle contraction

Abstract

Objective:

To determine normal limits and to analyse the test-retest reliability of the vestibular evoked myogenic potentials (VEMPs) parameters.

Methods:

The VEMP procedure was repeated on different test days to analyze test-retest differences. We calculated several reliability parameters: intraclass reliability coefficient (ICC), method error (ME), coefficient of variation of the method error (CV ${}_{\mathit{M}\mathit{E}}$ ), standard error of measurement (SEM) and minimal difference (MD) for test-retest measurements. Normal values for left-right differences, based on the interaural ratio (IAR), were determined.

Results:

For each VEMP parameter, the ICC values indicated excellent reliability, except for p13 and corrected amplitude (fair to good reliability). The CV ${}_{\mathit{M}\mathit{E}}$ values were less than 7% for p13, n23, threshold, MRV ${}_{\mathit{f}\mathit{e}\mathit{m}\mathit{a}\mathit{l}\mathit{e}\mathit{s}}$ and MRV ${}_{\mathit{m}\mathit{a}\mathit{l}\mathit{e}\mathit{s}}$ . For the parameters corrected amplitude and raw amplitude, the CV ${}_{\mathit{M}\mathit{E}}$ values exceeded 15%. The 95% IAR prediction intervals (PIs) were also largest for the parameters raw amplitude and corrected amplitude.

Conclusion:

In order to evaluate a VEMP outcome in a patient, the VEMP parameters and IAR values can be compared with the 95% PI of the normal values. When successive measurements are performed within the same subjects, the minimal difference (MD) serves as a tool to decide whether these differences are clinically relevant or not.