Novel Method for Vestibular Evoked Myogenic Potentials: Technique and Reproducibility

Objective: A novel method was employed to control the sternocleidomastoid muscle contraction level during vestibular evoked myogenic potential (VEMP) measurement. Study Design: A prospective study to measure the normal VEMP response. Settings: A pressure feedback device composed of a firm rubber bulb and a pressure gauge was employed to monitor the muscular contraction level during measurement. Methods: Nineteen normal-hearing subjects (12 males; mean age 34.0 +/- 7.7 years) were tested. Subjects were instructed to position the chin on the rubber bulb and use the neck flexors to maintain a pressure of 120 mm Hg during the measurement. Main Outcome Measures: The P13 latencies, N23 latencies, and P13-N23 amplitudes were recorded. In nine subjects, the reproducibility of the technique was tested weekly for 3 consecutive weeks. Results: The average (+/- SD) latency of P13 was 13.97 +/- 1.33 ms, and the latency of N23 was 24.03 +/- 1.79 ms. The average amplitude was 66.89 +/- 44.1 mV. There was no significant difference between right and left ears in P13 latencies, N23 latencies, and P13-N23 amplitudes. In nine subjects, the average measured interclass correlation coefficient was 0.97 in amplitude, 0.8 in P13 latency, and 0.93 in N23 latency in three consecutive weekly measurements. Conclusions: The chin-rest pressure feedback method is easy to perform during VEMP testing. Subjects can maintain a constant level of sternocleidomastoid contraction and neck flexion to facilitate this response with a high degree of test-retest reliability. This technique provides a means to compare VEMPs across different clinical scenarios over time.