The repeatability of oVEMP in response to low-frequency vibration against the vertex and forehead

Background: The measurement of ocular Vestibular Evoked Myogenic Potentials (oVEMP) is a novel method for investigating vestibular function. Stimulus and recording techniques vary in the literature. A standardized test procedure is desirable in order to ensure repeatable results.

Objective: To investigate the magnitude and repeatability of the asymmetry ratio (AR) of oVEMPs in response to low-frequency bone conducted vibration (BCV) applied to the forehead and vertex in a healthy population.

Methods: 20 healthy subjects were tested three times by stimulating with 125 Hz BCV at the forehead and the vertex. The first two tests were performed with the subject remaining in the examining room and the electrodes in place. After a short break, a third test was performed with a new set of electrodes. The AR was calculated for each test based on the evoked oVEMPs responses from the left and the right side. The AR magnitude, variance and repeatability coefficients were evaluated to determine which of the two stimulus sites is best suited in clinical use.

Results: Stimulation at the forehead resulted in a statistically significant lower median AR compared to the vertex. The forehead had lower repeatability coefficients, and statistically significantly lower variances.

Conclusions: This study indicates that the forehead is a better stimulation site than the vertex for low-frequency BCV in clinical use.