Noisy vestibular stimulation increases gait speed in normals and in bilateral vestibulopathy.

BACKGROUND: Galvanic vestibular stimulation delivered as zero-mean current noise (noisy GVS) has been shown to improve static and dynamic postural stability probably by enhancing vestibular information. OBJECTIVE: /Hypothesis: To examine the effect of an imperceptible level of noisy GVS on dynamic locomotion in normal subjects as well as in patients with bilateral vestibulopathy. METHODS: Walking performance of 19 healthy subjects and 12 patients with bilateral vestibulopathy at their preferred speed was examined during application of noisy GVS with an amplitude ranging from 0 to 1000 µA. The gait velocity, stride length and stride time were analyzed. RESULTS: Noisy GVS had significant effects on gait velocity, stride length and stride time in healthy subjects as well as in patients with bilateral vestibulopathy (p < 0.05). The optimal amplitude of noisy GVS improved gait velocity by 10.9 ±â€¯1.2%, stride length by 5.7 ±â€¯1.2% and stride time by 4.6 ±â€¯7% (p < 0.0001) compared to the control session in healthy subjects. The optimal stimulus improved gait velocity by 12.8 ±â€¯1.3%, stride length by 8.3 ±â€¯1.1% and stride time by 3.7 ±â€¯7% (p < 0.0001) in patients with bilateral vestibulopathy. The improved values of these parameters of locomotion by noisy GVS in the patients were not significantly different from those in healthy subjects in the control condition (p > 0.4). CONCLUSION: Noisy GVS is effective in improving gait performance in healthy subjects as well as in patients with bilateral vestibulopathy.

The diagnostic value of vestibular evoked myogenic potentials in patients with Meniere's disease.

OBJECTIVE: To estimate the sensitivity and specificity of vestibular evoked myogenic potentials (VEMPs) in comparison with caloric test in diagnosing Meniere's disease (MD) among patients with dizziness. METHODS: Data were retrospectively collected from 1,170 consecutive patients who underwent vestibular tests. Among them, 114 patients were diagnosed as having unilateral definite MD. VEMPs in response to clicks and short tone burst stimulation as well as caloric tests were performed. The sensitivity and specificity of each test were evaluated. The results of each test were compared with hearing level and staging of MD. RESULTS: The sensitivity and specificity of VEMPs were 50.0% and 48.9%, while those of the caloric test were 37.7% and 51.2%, respectively. There was no significant difference in hearing level between patients appropriately or inappropriately identified by VEMPs, whereas there was a significant difference in those of the caloric test. Combined use of VEMP and caloric test increased the sensitivity to 65.8%. CONCLUSION: Although the sensitivity and specificity of VEMPs in diagnosing MD were not high, they were comparable to those of caloric test. VEMPs as well as caloric testing may give additional information as part of a diagnostic test battery for detecting vestibular abnormalities in MD.

Ocular vestibular evoked myogenic potentials in response to air-conducted sound and bone-conducted vibration in vestibular schwannoma.

OBJECTIVE: To clarify the origin and pathways of ocular vestibular evoked myogenic potentials (oVEMPs) to air-conducted sound (ACS), we compared the results of oVEMPs with ACS, with oVEMPs with bone-conducted vibration (BCV), cervical VEMPs (cVEMPs) with ACS, and the caloric test in patients with unilateral vestibular schwannoma (VS). STUDY DESIGN: Retrospective review. SETTING: Tertiary referral center. PATIENTS: Forty-five patients with untreated unilateral VS. MAIN OUTCOME MEASURE: Each patient underwent vestibular tests, including oVEMPs to ACS, oVEMPs to BCV, cVEMPs to ACS, and caloric tests. The correlations among these tests were evaluated. RESULTS: Of the 45 patients recruited, 28 patients (63%) showed reduced or absent oVEMPs to ACS solely on the affected side. There were no significant differences in abnormal response ratios among oVEMPs to ACS, oVEMPs to BCV, cVEMPs to ACS, or the caloric test. The results of oVEMPs to ACS had a significant correlation with those of oVEMPs to BCV and the caloric test (p < 0.05) but not with those of cVEMPs to ACS (p > 0.05). CONCLUSION: These findings support the hypothesis that oVEMP in response to ACS are predominantly mediated by the superior vestibular nerve and probably reflect the function of the utricle.

Ocular vestibular evoked myogenic potential elicited from binaural air-conducted stimulations: clinical feasibility in patients with peripheral vestibular dysfunction.

CONCLUSION: Ocular vestibular evoked myogenic potentials (oVEMPs) to binaural air-conducted stimulation (ACS) may provide a convenient way of assessing the crossed vestibulo-ocular reflex in patients with vestibular dysfunction as well as in healthy subjects. OBJECTIVE: To investigate the clinical feasibility of using oVEMPs in response to binaural ACS to assess normal subjects and patients with vestibular dysfunction. METHODS: The study investigated 24 normal subjects (14 men and 10 women, aged from 23 to 60 years) and 14 patients with unilateral peripheral vestibular dysfunction. Each subject underwent oVEMP testing in response to monaural ACS and binaural ACS (500 Hz tone burst, 135 dBSPL). RESULTS: In normal subjects, bilateral oVEMPs were elicited in 75% of subjects in response to monaural ACS and in 91% in response to binaural ACS. Asymmetry ratios (ARs) of the responses to binaural ACS were significantly smaller than those of the responses to monaural ACS (p < 0.01). In patients with unilateral vestibular dysfunction, there were no significant differences in the amplitude, latency, or AR of the responses between monaural and binaural ACS. Approximately 30% of patients showed reduced ARs to binaural ACS relative to monaural ACS, primarily due to contamination by uncrossed responses elicited in healthy ears.

The mitochondrial A3243G mutation involves the peripheral vestibule as well as the cochlea.

OBJECTIVES/HYPOTHESIS: To evaluate vestibular function in patients with the mitochondrial A3243G mutation. STUDY DESIGN: Data from patients with the A3243G mutation attending an academic tertiary referral center were prospectively recorded. METHODS: The clinical histories of 13 unrelated patients with the mitochondrial A3243G mutation (six mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes; and seven maternally inherited diabetes and deafness) were recorded, in particular their history of vestibular symptoms. Vestibular examinations including caloric testing and vestibular evoked myogenic potentials in response to air-conducted sound (ACS-VEMPs) were performed. In seven patients who showed abnormal ACS-VEMP, VEMP in response to galvanic stimuli (galvanic-VEMP) were also recorded. RESULTS: Eleven of the 13 patients had vestibular symptoms. The age of onset of vestibular symptoms was significantly later than the ages of onset of hearing loss and diabetes mellitus (P < .05). Ten of the 13 patients showed abnormal caloric responses, whereas 12 patients showed abnormal ACS-VEMPs on one or both sides. All of the seven patients who underwent galvanic-VEMP testing showed normal responses. CONCLUSIONS: The A3243G mutation is associated with vestibular dysfunction involving both the superior and inferior vestibular nerve systems. Furthermore, our results from galvanic-VEMP testing suggests that a labyrinthine lesion is primarily responsible for the symptoms of vestibular dysfunction.