The vestibular evoked myogenic potential (VEMP) has been shown to be clinically useful in providing diagnostic information regarding the function of the otolith receptors, inferior vestibular nerve, and vestibulospinal pathways. The VEMP is a biphasic response elicited by loud clicks or tone bursts and recorded from the tonically contracted sternocleidomastoid (SCM) muscle. Because the VEMP is an inhibitory response, it is important to investigate stimulus and parameter characteristics in order to determine the optimal test protocol and maximize clinical usefulness. The aims of this study were 1) to evaluate the effects of 4 different methods of SCM muscle activation and the effect of visual biofeedback on VEMP latency, amplitude, asymmetry ratio, mean rectified EMG level, and difficulty ratings, and 2) to determine the influence of SCM muscle activation pattern and visual biofeedback level on test-retest reliability. Forty-eight healthy volunteers between the ages of 18 and 50 underwent VEMP testing using each of the following muscle activation patterns: supine with the head raised (SE), supine with the head turned away from the test ear (SR), supine with the head raised and turned away from the test ear (SER), and sitting with the head turned away from the test ear (SitR). Testing subjects with the SER method yielded the most robust amplitude response and sternocleidomastoid EMG activity. No statistically significant differences were found in interaural asymmetry ratios among the 4 methods of SCM activation. Subjects rated the SE and SER methods as more difficult than the SE and SitR methods at each of the 3 target levels. Test-retest reliability was high for P1/N1 amplitude and mean rectified EMG levels when subjects were provided visual biofeedback to monitor the level of tonic SCM muscle activity. The study demonstrates the importance of providing patients a means of monitoring and maintaining the amplitude of the rectified EMG at a constant target level during SCM muscle activation. Although no evidence to reject or strongly favor a specific method was found, monaural-ipsilateral recording with the SitR method was found to be advantageous for individuals with weakness or decreased endurance for sustained muscle contraction.

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Objective: The purpose of this study was to investigate the effects of noise exposure on the cervical vestibular evoked myogenic potential (cVEMP) in individuals with asymmetric noise-induced sensorineural hearing loss (NIHL). Design: A cross-sectional observational study was used to compare cVEMP characteristics in 43 individuals with a history of noise exposure greater in one ear (e.g., the left ear of a right-handed rifle shooter) and asymmetric sensorineural hearing loss consistent with the history of noise exposure and in 14 age-matched controls. The characteristics of hearing loss were examined further for the noise-exposed participants with abnormal cVEMPs and the noise-exposed participants with normal cVEMPs. Results: Thirty-three percent of the noise-exposed participants had abnormal cVEMPs, whereas cVEMPs were present and symmetrical in 100% of the age-matched controls, and cVEMP threshold was greater in the noise-exposed group than in the control group. Abnormal cVEMPs occurred most often in the ears with poorer hearing (or greater NIHL), and the noise-exposed participants who had abnormal cVEMPs had poorer high-frequency pure-tone thresholds (greater NIHL) and greater interaural high-frequency pure-tone threshold differences than the noise-exposed participants with normal cVEMPs. Conclusions: These findings are consistent with previous studies that suggest that the sacculocollic pathway may be susceptible to noise-related damage. There is emerging evidence that the severity of NIHL is associated with the presence or absence of cVEMPs.