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OBJECTIVE: Velocity storage mechanism is a multisensory rotation estimator; it compensates for errors in the information provided by the peripheral vestibular organs by means of an adjustment in the duration of the vestibular signal. The aim of this study was to determine the activity of the velocity storage mechanism in the presence of a labyrinthine disorder, using galvanic vestibular stimulation to cause direct activation of the vestibular afferent neurons. MATERIALS and METHODS: Forty-one subjects with definite Meniere's disease (MD) and 36 healthy volunteers were evaluated using a 20-s galvanic vestibular stimulation. RESULTS: We found a post-stimulus nystagmus overshoot exclusively in subjects with MD (47% in subjects with unilateral disease and 82% in subjects with bilateral disease), but no overshoot in healthy subjects. CONCLUSION: Because post-stimulus nystagmus overshoot is caused by the velocity storage mechanism, this finding suggests an increase in the velocity storage in subjects with a labyrinthine disease. [ABSTRACT FROM AUTHOR]

Objectives: The aim of this study is to record the VEMP changes that occur in patients with vestibular schwannoma to assess vestibulospinal reflexes. Material and Methods: This study was carried on fifteen patients with vestibular schwannoma. Fifteen persons not suffering from any vestibulo-cochlear problem were subjected to VEMP recordings as controls. Results: In this study, 3 patients (20%) had no VEMP waves on the affected side (but the waves were preserved on the other side), 11 patients (73.4%) had no VEMP waves bilaterally, and 1 patient (6.6%) had VEMP waves preserved on both sides As for the latencies of p1, n1 waves and peak to peak amplitude variation, VEMP could be elicited only in 4 patients (26.8%). There was a significant difference between the patients and controls in regard to mean p1 and n1 latencies but there was no significant difference between the peak amplitudes of patients and controls. Conclusion: VEMP can be a good indicator for the function of the vestibulospinal reflexes than other physiological examinations in cases of vestibular schwannoma. [ABSTRACT FROM AUTHOR]

Objective: To compare VEMP response characteristics between binaural and monaural stimulation and to determine normative data for logon stimulus in adults. Subjects and Methods: Twenty-two healthy adults were involved in the study. Two set types of VEMP recordings were performed for each subject. One is simultaneous binaural logon stimulation with bilateral recordings (B-VEMP) and the other one is monaural logon stimulation of each ear separately with two sequential ipsilateral recording (M-VEMP). Subjects were divided into two groups involving 11 participants in each group. In the first group all participants underwent initial B-VEMP test and subsequent M-VEMP test; while in the second group all participants underwent initial M-VEMP test and subsequent BVEMP test. Logon type stimulus with 120 dB HL intensity was used to trigger VEMPs in both methods. Results: There was no statistical difference between B-VEMP and M-VEMP recordings in respect to P1 and N1 latencies, P1- N1 interval and P1-N1 amplitude in any of the groups. When the VEMP responses of 2 groups were combined (42 ears), we have found that the mean P1 latency was 14.9 ± 1.5 msec, the mean N1 latency was 22.3 ± 2.3 msec, the mean P1-N1 interval was 7.6 ± 2.4 msec, and the mean P1-N1 amplitude was 14.1 ± 6.1 μV for B-VEMP recordings. These values were 15.1 ± 1.6 msec, 22.2 ± 1.6 msec, 7.0 ± 1.9 msec, and 14.8 ± 6.0 μV respectively for M-VEMP recordings. Conclusion: Binaural stimulation with simultaneous bilateral recording gives similar results with monaural stimulation with a separate recording for each site. B-VEMP recording can be a more convenient way of VEMP testing especially in those subjects who have difficulty to maintain a constant muscular effort during test procedure. [ABSTRACT FROM AUTHOR]