OBJECTIVE: Because a continuous muscular effort is required during recording of vestibular-evoked myogenic potentials, we assume vestibular-evoked myogenic potentials elicited by simultaneous bilateral clicks can be used as a more convenient mode compared with respective unilateral clicks. To investigate whether bilateral clicks provide the same information as unilateral clicks, we examined whether the responses are different between them in normal subjects and whether bilateral clicks have the same diagnostic value as vestibular-evoked myogenic potentials elicited by unilateral clicks in detecting retrolabyrinthine lesions. STUDY DESIGN: Prospective study. SETTING: Academic tertiary referral center. SUBJECTS: Fourteen healthy volunteers and four patients with unilateral cerebellopontine angle tumors were enrolled in this study. INTERVENTIONS: Recordings of vestibular-evoked myogenic potential responses. MAIN OUTCOME MEASURES: The latency of each peak (p13, n23), the peak-to-peak interval, and amplitude (p13-n23). RESULTS: Both unilateral and bilateral click stimulation of 28 ears (100%) produced vestibular-evoked myogenic potentials in normal subjects. The mean latencies of p13 and n23, peak-to-peak interval, and amplitude of vestibular-evoked myogenic potentials elicited with unilateral clicks were 11.62 +/- 0.99 ms, 19.74 +/- 1.30 ms, 8.12 +/- 1.66 ms, and 110.79 +/- 61.37 microV, respectively, whereas those elicited with bilateral clicks were 11.16 +/- 0.51 ms, 19.22 +/- 1.61 ms, 8.06 +/- 1.66 ms, and 111.77 +/- 40.98 microV, respectively. There was a significant difference (p < 0.05) in the latencies, but not for the interval and amplitude (p > 0.05). Four patients with unilateral cerebellopontine angle tumors and prolonged latencies of unilateral clicks vestibular-evoked myogenic potentials also showed latency prolongation in bilateral clicks vestibular-evoked myogenic potentials. CONCLUSION: Although the use of bilateral acoustic stimulation shortens the vestibular-evoked myogenic potential latencies in normal subjects, it does not affect the bilateral clicks vestibular-evoked myogenic potential ability to detect retrolabyrinthine lesions. Bilateral clicks vestibular-evoked myogenic potentials are a more convenient mode with which to help diagnose both labyrinthine and retrolabyrinthine lesions than unilateral clicks vestibular-evoked myogenic potentials.
OBJECTIVE: Because a continuous muscular effort is required during recording of vestibular-evoked myogenic potentials, we assume vestibular-evoked myogenic potentials elicited by simultaneous bilateral clicks can be used as a more convenient mode compared with respective unilateral clicks. To investigate whether bilateral clicks provide the same information as unilateral clicks, we examined whether the responses are different between them in normal subjects and whether bilateral clicks have the same diagnostic value as vestibular-evoked myogenic potentials elicited by unilateral clicks in detecting retrolabyrinthine lesions. STUDY DESIGN: Prospective study. SETTING: Academic tertiary referral center. SUBJECTS: Fourteen healthy volunteers and four patients with unilateral cerebellopontine angle tumors were enrolled in this study. INTERVENTIONS: Recordings of vestibular-evoked myogenic potential responses. MAIN OUTCOME MEASURES: The latency of each peak (p13, n23), the peak-to-peak interval, and amplitude (p13-n23). RESULTS: Both unilateral and bilateral click stimulation of 28 ears (100%) produced vestibular-evoked myogenic potentials in normal subjects. The mean latencies of p13 and n23, peak-to-peak interval, and amplitude of vestibular-evoked myogenic potentials elicited with unilateral clicks were 11.62 +/- 0.99 ms, 19.74 +/- 1.30 ms, 8.12 +/- 1.66 ms, and 110.79 +/- 61.37 microV, respectively, whereas those elicited with bilateral clicks were 11.16 +/- 0.51 ms, 19.22 +/- 1.61 ms, 8.06 +/- 1.66 ms, and 111.77 +/- 40.98 microV, respectively. There was a significant difference (p < 0.05) in the latencies, but not for the interval and amplitude (p > 0.05). Four patients with unilateral cerebellopontine angle tumors and prolonged latencies of unilateral clicks vestibular-evoked myogenic potentials also showed latency prolongation in bilateral clicks vestibular-evoked myogenic potentials. CONCLUSION: Although the use of bilateral acoustic stimulation shortens the vestibular-evoked myogenic potential latencies in normal subjects, it does not affect the bilateral clicks vestibular-evoked myogenic potential ability to detect retrolabyrinthine lesions. Bilateral clicks vestibular-evoked myogenic potentials are a more convenient mode with which to help diagnose both labyrinthine and retrolabyrinthine lesions than unilateral clicks vestibular-evoked myogenic potentials.