The vestibular evoked myogenic potential: a test-retest reliability study.

OBJECTIVE: The purpose of this study was to evaluate the reliability of the vestibular evoked myogenic potential (VEMP) response in a clinical setting when only a feedback mechanism is available for monitoring background EMG.

METHODS: Sixty-one healthy subjects participated in the investigation of the within-session reliability, whereas fourteen of them were retested after one week for examination of the between-session reliability. VEMPs were recorded using 500 Hz tone bursts with the subjects in a sitting position and their heads turned away from the test ear to the contralateral shoulder, thereby pushing their chin against the inflatable cuff of a blood pressure manometer, serving as feedback method.

RESULTS: The feedback method revealed latency and amplitude values comparable to other data in the literature where different test conditions were applied. Excellent reliability with ICC values ranging from 0.78 to 0.96 and CV(ME) values ranging from 4% to 36%, was achieved for P1 and N1 latency, threshold and interpeak amplitude. Good reliability with ICC values of 0.65 and 0.68 and CV(ME) values of 170% and 189%, was obtained for the asymmetry ratio.

CONCLUSIONS: A unilateral muscle contraction controlled by a feedback mechanism resulted in reliable response parameters, comparable right to left and corresponding to literature data obtained in different test conditions.

SIGNIFICANCE: The use of a blood pressure manometer as feedback mechanism combined with a meticulously controlled positioning of the head and contraction of the SCM muscle provides a reliable alternative in clinical settings, when the background muscle contraction cannot be measured or software related correction algorithms are not accessible.