Aging effect on galvanic vestibular-evoked myogenic potentials

Intermediate Latency-Evoked Potentials of Multimodal Cortical Vestibular Areas: Galvanic Stimulation

Introduction

Human multimodal vestibular cortical regions are bilaterally anterior insulae and posterior opercula, where characteristic vestibular-related cortical potentials were previously reported under acoustic otolith stimulation. Galvanic vestibular stimulation likely influences semicircular canals preferentially. Galvanic stimulation was compared to previously established data under acoustic stimulation.

Methods

14 healthy right-handed subjects, who were also included in the previous acoustic potential study, showed normal acoustic and galvanic vestibular-evoked myogenic potentials. They received 2,000 galvanic binaural bipolar stimuli for each side during EEG recording.

Results

Vestibular cortical potentials were found in all 14 subjects and in the pooled data of all subjects (“grand average”) bilaterally. Anterior insula and posterior operculum were activated exclusively under galvanic stimulation at 25, 35, 50, and 80 ms; frontal regions at 30 and 45 ms. Potentials at 70 ms in frontal regions and at 110 ms at all of the involved regions could also be recorded; these events were also found using acoustic stimulation in our previous study.

Conclusion

Galvanic semicircular canal stimulation evokes specific potentials in addition to those also found with acoustic otolith stimulation in identically located regions of the vestibular cortex. Vestibular cortical regions activate differently by galvanic and acoustic input at the peripheral sensory level.

Significance

Differential effects in vestibular cortical-evoked potentials may see clinical use in specific vertigo disorders.

Promontory electrical stimulation to elicit vestibular evoked myogenic potentials (VEMPs)

CONCLUSION

Vestibular evoked myogenic potentials (VEMPs) provoked electrically at the promontory provide a feasible method to record vestibular responses in awake patients.

OBJECTIVES

Electrically evoked VEMP testing has been performed by galvanic stimulation at the mastoid so far. The present study examined an electrical stimulation mode close to the otolith organs at the promontory.

METHODS

Fourteen cochlear implant candidates who were planned for clinical routine promontory stimulation testing (PST) to assess auditory nerve function underwent promontory VEMP testing. After testing the cochlear nerve function during PST promontory cervical VEMPs (p-c-VEMPs) and promontory ocular VEMPs (p-o-VEMPs) were recorded during subsequent transtympanic electrical stimulation at the promontory.

RESULTS

Promontory VEMP testing was well tolerated by the patients. Mean latencies for p-c-VEMPs were 10.30 ± 2.23 ms (p1) and 17.86 ± 3.83 ms (n1). Mean latencies for p-o-VEMPs were 7.64 ± 1.24 ms (n1) and 11.2 ± 1.81 ms (p1). The stimulation threshold level was measured at 0.15 ± 0.07 mA for p-c-VEMPs and at 0.19 ± 0.11 mA for p-o-VEMPs. The discomfort level was found to be at 0.78 ± 0.29 mA for p-c-VEMPs and at 0.69 ± 0.25 mA for p-oVEMPs. Mean p1-n1 amplitude in p-c-VEMPs was 124.78 ± 56.55 µV and p-o-VEMPs showed a mean n1-p1 amplitude of 30.94 ± 18.98 µV.

Application of intermittent galvanic vestibular stimulation reveals age-related constraints in the multisensory reweighting of posture

In this study we examined the effects of intermittent short-duration Galvanic Vestibular Stimulation (GVS) during a multisensory perturbation of posture in young and elderly adults. Twelve young (24.91±6.44 years) and eleven elderly (74.8±6.42 years) participants stood upright under two task conditions: (a) quiet standing and (b) standing while receiving pseudo-randomly presented bipolar 2 s GVS pulses. In both conditions, sensory reweighting was evoked by visual surround oscillations (20 cm, 0.3 Hz) and Achilles tendon vibration (3 mm, 80 Hz), concurrently delivered during the middle 60 s of standing. Intermittent GVS decreased the excessive postural sway induced by the concurrent visual and proprioceptive perturbation in young but not in elderly participants. It is suggested that GVS increases sensory reliance on the vestibular system while elderly adults are less able to exploit this stimulation in order to reduce the destabilizing effect of the multisensory perturbation on their posture.

Feasibility of simultaneous recording of cervical and ocular vestibular-evoked myogenic potentials via galvanic vestibular stimulation

CONCLUSION

Simultaneous galvanic vestibular stimulation (GVS)-cervical vestibular-evoked myogenic potential (cVEMP) and GVS-ocular (oVEMP) tests yielded similar information to that obtained in individual tests.

OBJECTIVE

This study compared the characteristic parameters of cVEMPs and oVEMPs via GVS between individual and simultaneous recording patterns in healthy and elderly subjects. Consequently, the effectiveness of simultaneous GVS-cVEMP and GVS-oVEMP tests was assessed.

METHODS

A total of 24 healthy and 16 elderly subjects were enrolled in this study. All participants underwent individual cVEMP, individual oVEMP, and simultaneous cVEMP and oVEMP testing via GVS mode in a random order. The response rates and characteristic parameters of cVEMPs and oVEMPs between individual and simultaneous tests, including latencies, intervals, and amplitudes, were measured.

RESULTS

The VEMP parameters, including latencies, intervals, and amplitudes, all demonstrated no significant differences between individual and simultaneous tests (p > 0.05, paired t test), either in healthy or elderly subjects. Pearson's correlation analyses also revealed significant positive correlations in all parameters between these two tests (p < 0.05).

Discrepancy in the involution of the different neural loops with age

The purpose of the study was to compare the effects of sensory manipulations on postural control for subjects of different ages. A young group of subjects (n = 17; 20.0 ± 1.3 years) and an old group of subjects (n = 17; 74.7 ± 6.3 years) were compared in 14 postural conditions [2 reference conditions and 12 sensory manipulation conditions: eyes closed, cervical collar, tendon vibration, electromyostimulation, galvanic vestibular stimulation (2 designs), foam surface] on a force platform. Spatio-temporal parameters of the center of foot pressure displacement were analyzed. When vestibular or proprioceptive afferences were manipulated, the old group was more disturbed than the young group. In addition, when myo-articular proprioceptive afferences were the only non-manipulated information source, the old group was also more disturbed than the young group. Hence, the inability to correctly interpret proprioceptive information and/or the impairment of myo-articular information would appear to be the major factor causing postural control deterioration. Moreover, concerning the vestibular system, it may be that aging alters the central integration of vestibular afferences. These results suggest that aging differently affects the functional ability of the different neural loops in postural control.

Age-related changes in ocular vestibular-evoked myogenic potentials via galvanic vestibular stimulation and bone-conducted vibration modes

CONCLUSION

The age-related changes in ocular vestibular-evoked myogenic potentials (oVEMPs) elicited by galvanic vestibular stimulation (GVS) and bone-conducted vibration (BCV) might be attributed to the morphological degeneration of the vestibular system.

OBJECTIVE

This study employed GVS and BCV modes for eliciting oVEMPs in healthy subjects to explore the effect of aging on the vestibulo-ocular reflex (VOR) pathway.

METHODS

Sixty-nine healthy subjects (aged 22-69 years) were divided into 5 groups of 12-19 subjects by decades of age. All subjects underwent oVEMPs using GVS and BCV modes. The prevalence and parameters of oVEMPs, including nI latency, pI latency, nI-pI interval, and nI-pI amplitude were measured and compared.

RESULTS

The prevalences of GVS-oVEMPs had nonsignificant differences among all age groups, whereas that of BCV-oVEMPs in the over-60 group was significantly lower than those in the under-60 groups. In GVS-oVEMPs, the group over 60 years had significantly longer nI, pI latencies, and smaller amplitudes when compared with those under 60 years. In BCV-oVEMPs, the nI and pI latencies in the over-60 group were significantly longer than those of the under-60 groups, while the nI-pI amplitudes of groups over 50 years were significantly smaller than those of groups under 50 years. All oVEMP parameters exhibited significant differences between GVS- and BCV-oVEMPs in each age group.