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Chen ZC, Zhang YZ, Zhao HD, Wei X, Murofushi T, Hu J, Cheng Y, Chen FY, Xu XD, Xu M, Zhang Q. Retro-labyrinthine Lesion Site Detected by Galvanic Vestibular Stimulation Elicited Vestibular-evoked Myogenic Potentials in Patients with Auditory Neuropathy. Curr Med Sci 2021; 41:695-704. [PMID: 34403094 DOI: 10.1007/s11596-021-2411-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2021] [Accepted: 07/18/2021] [Indexed: 10/20/2022]
Abstract
OBJECTIVE Auditory neuropathy (AN) is a unique pattern of hearing loss with preservation of hair cell function. The condition is characterized by the presence of otoacoustic emissions (OAE) or cochlear microphonic (CM) responses with severe abnormalities of the auditory brainstem response (ABR). The vestibular branches of the VIII cranial nerve and the structures innervated by it can also be affected. However, the precise lesion sites in the vestibular system are not well characterized in patients with AN. METHODS The air-conducted sound (ACS) vestibular-evoked myogenic potentials (VEMPs) and galvanic vestibular stimuli (GVS)-VEMPs were examined in 14 patients with AN. RESULTS On examination of VEMPs (n=14, 28 ears), the absent rates of ACS-cervical VEMP (cVEMP), ACS-ocular VEMP (oVEMP), GVS-cVEMP, GVS-oVEMP and caloric test were 92.9% (26/28), 85.7% (24/28), 67.9% (19/28), 53.6% (15/28), and 61.5% (8/13), respectively. Impaired functions of the saccule, inferior vestibular nerve, utricle, superior vestibular nerve, and horizontal semicircular canal were found in 25.0% (7/28), 67.9% (19/28), 32.1% (9/28), 53.6% (15/28) and 61.5% (8/13) patients, respectively. On comparing the elicited VEMPs parameters of AN patients with those of normal controls, both ACS-VEMPs and GVS-VEMPs showed abnormal results in AN patients (such as, lower presence rates, elevated thresholds, prolonged latencies, and decreased amplitudes). CONCLUSION The study suggested that patients with AN often have concomitant vestibular disorders. Retro-labyrinthine lesions were more frequently observed in this study. GVS-VEMPs combined with ACS-VEMPs may help identify the lesion sites and facilitate detection of areas of vestibular dysfunction in these patients.
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Affiliation(s)
- Zi-Chen Chen
- Department of Otorhinolaryngology, Head, and Neck Surgery, Second Affiliated Hospital of Xi'an Jiaotong University School of Medicine, Xi'an, 710000, China.,Department of Otorhinolaryngology-Head and Neck Surgery, Xinhua Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, 200082, China.,Shanghai Jiaotong University School of Medicine Ear Institute, Shanghai, 200082, China.,Shanghai Key Laboratory of Translational Medicine on Ear and Nose Diseases, Shanghai, 200082, China
| | - Yu-Zhong Zhang
- Department of Otorhinolaryngology, Head, and Neck Surgery, Second Affiliated Hospital of Xi'an Jiaotong University School of Medicine, Xi'an, 710000, China.,Department of Otorhinolaryngology-Head and Neck Surgery, Xinhua Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, 200082, China.,Shanghai Jiaotong University School of Medicine Ear Institute, Shanghai, 200082, China.,Shanghai Key Laboratory of Translational Medicine on Ear and Nose Diseases, Shanghai, 200082, China
| | - Huan-di Zhao
- Department of Otorhinolaryngology, Head, and Neck Surgery, Second Affiliated Hospital of Xi'an Jiaotong University School of Medicine, Xi'an, 710000, China
| | - Xinyu Wei
- Department of Otorhinolaryngology, Head, and Neck Surgery, Second Affiliated Hospital of Xi'an Jiaotong University School of Medicine, Xi'an, 710000, China
| | - Toshihisa Murofushi
- Department of Otolaryngology, Teikyo University School of Medicine Mizonokuchi Hospital, Kawasaki, 213-0001, Japan
| | - Juan Hu
- Department of Otorhinolaryngology, Head, and Neck Surgery, Second Affiliated Hospital of Xi'an Jiaotong University School of Medicine, Xi'an, 710000, China
| | - Ying Cheng
- Department of Otorhinolaryngology, Head, and Neck Surgery, Second Affiliated Hospital of Xi'an Jiaotong University School of Medicine, Xi'an, 710000, China
| | - Fei-Yun Chen
- Department of Otorhinolaryngology, Head, and Neck Surgery, Second Affiliated Hospital of Xi'an Jiaotong University School of Medicine, Xi'an, 710000, China
| | - Xin-da Xu
- Department of Otorhinolaryngology, Affiliated Ophthalmology and Otolaryngology Hospital of Fudan University, Shanghai, 200082, China
| | - Min Xu
- Department of Otorhinolaryngology, Head, and Neck Surgery, Second Affiliated Hospital of Xi'an Jiaotong University School of Medicine, Xi'an, 710000, China.
| | - Qing Zhang
- Department of Otorhinolaryngology, Head, and Neck Surgery, Second Affiliated Hospital of Xi'an Jiaotong University School of Medicine, Xi'an, 710000, China. .,Department of Otorhinolaryngology-Head and Neck Surgery, Xinhua Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, 200082, China. .,Shanghai Jiaotong University School of Medicine Ear Institute, Shanghai, 200082, China. .,Shanghai Key Laboratory of Translational Medicine on Ear and Nose Diseases, Shanghai, 200082, China.
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Merchant SH, Vial F, Leodori G, Fahn S, Pullman SL, Hallett M. A novel exaggerated "spino-bulbo-spinal like" reflex of lower brainstem origin. Parkinsonism Relat Disord 2018; 61:34-38. [PMID: 30316728 DOI: 10.1016/j.parkreldis.2018.10.007] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/19/2018] [Revised: 10/02/2018] [Accepted: 10/04/2018] [Indexed: 11/26/2022]
Abstract
BACKGROUND Many different oligosynaptic reflexes are known to originate in the lower brainstem which share phenomenological and neurophysiological similarities. OBJECTIVE To evaluate and discuss the differences and aberrancies among these reflexes, which are hard to discern clinically using neurophysiological investigations with the help of a case report. METHODS We describe the clinical and neurophysiological assessment of a young man who had a childhood history of opsoclonus-myoclonus syndrome with residual mild ataxia and myoclonic jerks in the distal extremities presenting with subacute onset total body jerks sensitive to sound and touch (in a limited dermatomal distribution), refractory to medications. RESULTS Based on clinical characteristics and insights gained from neurophysiological testing we could identify a novel reflex of caudal brainstem origin. CONCLUSIONS The reflex described is likely an exaggerated normal reflex, likely triggered by a dolichoectatic vertebral arterial compression and shares characteristics of different reflexes known to originate in caudal brainstem, which subserve distinctive roles in human postural control.
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Affiliation(s)
- Shabbir Hussain Merchant
- Human Motor Control Section, National Institute of Neurological Disorders and Stroke, National Institute of Health, Bethesda, MD, USA; Department of Neurology, Medical University of South Carolina, Charleston, SC, USA.
| | - Felipe Vial
- Human Motor Control Section, National Institute of Neurological Disorders and Stroke, National Institute of Health, Bethesda, MD, USA; Facultad de Medicina, Clínica Alemana Universidad del Desarrollo, Santiago, Chile
| | | | - Stanley Fahn
- Department of Neurology, College of Physicians and Surgeons, Columbia University, New York, NY, USA
| | - Seth L Pullman
- Department of Neurology, College of Physicians and Surgeons, Columbia University, New York, NY, USA
| | - Mark Hallett
- Human Motor Control Section, National Institute of Neurological Disorders and Stroke, National Institute of Health, Bethesda, MD, USA
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Cheng Y, Kimura Y, Kaga K. A study on vestibular-evoked myogenic potentials via galvanic vestibular stimulation in normal people. J Otol 2017; 13:16-19. [PMID: 29937861 PMCID: PMC6002623 DOI: 10.1016/j.joto.2017.09.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2017] [Revised: 09/15/2017] [Accepted: 09/27/2017] [Indexed: 11/04/2022] Open
Abstract
Objectives The aim of our study is to examine vestibular-evoked myogenic potentials (VEMPs) elicited by the galvanic vestibular stimulation in the sternocleidomastoid muscle (SCM) in healthy subjects for clinical applications of auditory neuropathy or vestibular neuropathy in the future. Methods We enrolled sixteen healthy subjects to record the average responses of SCM to galvanic vestibular stimulation (GVS) [current 3 mA; duration 1 ms] by electromyography (EMG). SPSS18.0 software was used to analyze the obtained data for mean and standard deviation. Results In all healthy subjects mastoid-forehead galvanic vestibular stimulation produced a positive-negative biphasic EMG responses on SCM ipsilateral to the cathodal electrode. The latency of p13 was 11.7 ± 3.0 ms. The latency of n23 was 17.8 ± 3.4 ms. The amplitude of p13-n23 was 147.0 ± 69.0 μV. The interaural asymmetry ratio (AR) of p13, n23 latency and the amplitude was respectively 0.12 ± 0.09, 0.08 ± 0.08 and 0.16 ± 0.10. Discussions Galvanic vestibular stimulation could elicit biphasic EMG responses from SCM via the vestibular nerve but not from the otolith organs. Galvanic stimulation together with air conducted sound (ACS) or bone conducted vibration (BCV) can elicit VEMPs and may enable the differentiation of retrolabyrinthine lesions from labyrinthine lesions in vestibular system.
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Affiliation(s)
- Ying Cheng
- National Institute of Sensory Organs, Tokyo Medical Center, Japan.,The Department of Otolaryngology Head and Neck Surgery in the Second Affiliated Hospital of Xi 'an Jiaotong University, Shaanxi Province, PR China
| | - Yusuke Kimura
- National Institute of Sensory Organs, Tokyo Medical Center, Japan
| | - Kimitaka Kaga
- National Institute of Sensory Organs, Tokyo Medical Center, Japan
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Lam CK, Staines WR, Tokuno CD, Bent LR. The medium latency muscle response to a vestibular perturbation is increased after depression of the cerebellar vermis. Brain Behav 2017; 7:e00782. [PMID: 29075558 PMCID: PMC5651382 DOI: 10.1002/brb3.782] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/20/2016] [Revised: 06/06/2017] [Accepted: 06/12/2017] [Indexed: 12/20/2022] Open
Abstract
INTRODUCTION Galvanic vestibular stimulation (GVS) is able to evoke distinct responses in the muscles used for balance. These reflexes, termed the short (SL) and medium latency (ML) responses, can be altered by sensory input; decreasing in size when additional sensory cues are available. Although much is known about these responses, the origin and role of the responses are still not fully understood. It has been suggested that the cerebellum, a structure that is involved in postural control and sensory integration, may play a role in the modulation of these reflexes. METHODS The cerebellar vermis was temporarily depressed using continuous theta burst stimulation and SL, ML and overall vestibular electromyographic and force plate shear response amplitudes were compared before and after cerebellar depression. RESULTS There were no changes in force plate shear amplitude and a non-significant increase for the SL muscle response (p = .071), however, we did find significant increases in the ML and overall vestibular muscle response amplitudes after cerebellar depression (p = .026 and p = .016, respectively). No changes were evoked when a SHAM stimulus was used. DISCUSSION These results suggest that the cerebellar vermis plays a role in the modulation of vestibular muscle reflex responses to GVS.
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Vestibular stimulation-induced facilitation of cervical premotoneuronal systems in humans. PLoS One 2017; 12:e0175131. [PMID: 28388686 PMCID: PMC5384664 DOI: 10.1371/journal.pone.0175131] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2016] [Accepted: 03/21/2017] [Indexed: 11/24/2022] Open
Abstract
It is unclear how descending inputs from the vestibular system affect the excitability of cervical interneurons in humans. To elucidate this, we investigated the effects of galvanic vestibular stimulation (GVS) on the spatial facilitation of motor-evoked potentials (MEPs) induced by combined pyramidal tract and peripheral nerve stimulation. To assess the spatial facilitation, electromyograms were recorded from the biceps brachii muscles (BB) of healthy subjects. Transcranial magnetic stimulation (TMS) over the contralateral primary motor cortex and electrical stimulation of the ipsilateral ulnar nerve at the wrist were delivered either separately or together, with interstimulus intervals of 10 ms (TMS behind). Anodal/cathodal GVS was randomly delivered with TMS and/or ulnar nerve stimulation. The combination of TMS and ulnar nerve stimulation facilitated BB MEPs significantly more than the algebraic summation of responses induced separately by TMS and ulnar nerve stimulation (i.e., spatial facilitation). MEP facilitation significantly increased when combined stimulation was delivered with GVS (p < 0.01). No significant differences were found between anodal and cathodal GVS. Furthermore, single motor unit recordings showed that the short-latency excitatory peak in peri-stimulus time histograms during combined stimulation increased significantly with GVS. The spatial facilitatory effects of combined stimulation with short interstimulus intervals (i.e., 10 ms) indicate that facilitation occurred at the premotoneuronal level in the cervical cord. The present findings therefore suggest that GVS facilitates the cervical interneuron system that integrates inputs from the pyramidal tract and peripheral nerves and excites motoneurons innervating the arm muscles.
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Fitzpatrick RC, Watson SRD. Passive motion reduces vestibular balance and perceptual responses. J Physiol 2016; 593:2389-98. [PMID: 25809702 DOI: 10.1113/jp270334] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2015] [Accepted: 03/10/2015] [Indexed: 11/08/2022] Open
Abstract
With the hypothesis that vestibular sensitivity is regulated to deal with a range of environmental motion conditions, we explored the effects of passive whole-body motion on vestibular perceptual and balance responses. In 10 subjects, vestibular responses were measured before and after a period of imposed passive motion. Vestibulospinal balance reflexes during standing evoked by galvanic vestibular stimulation (GVS) were measured as shear reaction forces. Perceptual tests measured thresholds for detecting angular motion, perceptions of suprathreshold rotation and perceptions of GVS-evoked illusory rotation. The imposed conditioning motion was 10 min of stochastic yaw rotation (0.5-2.5 Hz ≤ 300 deg s(-2) ) with subjects seated. This conditioning markedly reduced reflexive and perceptual responses. The medium latency galvanic reflex (300-350 ms) was halved in amplitude (48%; P = 0.011) but the short latency response was unaffected. Thresholds for detecting imposed rotation more than doubled (248%; P < 0.001) and remained elevated after 30 min. Over-estimation of whole-body rotation (30-180 deg every 5 s) before conditioning was significantly reduced (41.1 to 21.5%; P = 0.033). Conditioning reduced illusory vestibular sensations of rotation evoked by GVS (mean 113 deg for 10 s at 1 mA) by 44% (P < 0.01) and the effect persisted for at least 1 h (24% reduction; P < 0.05). We conclude that a system of vestibular sensory autoregulation exists and that this probably involves central and peripheral mechanisms, possibly through vestibular efferent regulation. We propose that failure of these regulatory mechanisms at different levels could lead to disorders of movement perception and balance control during standing.
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Affiliation(s)
- Richard C Fitzpatrick
- Neuroscience Research Australia and University of New South Wales, Sydney, Australia
| | - Shaun R D Watson
- Neuroscience Research Australia and University of New South Wales, Sydney, Australia.,Institute of Neurological Sciences, Prince of Wales Hospital, Sydney, Australia
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Park JJH, Shen A, Westhofen M. Promontory electrical stimulation to elicit vestibular evoked myogenic potentials (VEMPs). Acta Otolaryngol 2015; 135:239-45. [PMID: 25649883 DOI: 10.3109/00016489.2014.973530] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
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.
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Affiliation(s)
- Jonas J-H Park
- Department of Otorhinolaryngology and Head and Neck Surgery, University Hospital Aachen, RWTH Aachen University , Aachen , Germany
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Abstract
OBJECTIVE To investigate the repeatability of sound-evoked vestibular evoked myogenic potentials recorded from the triceps (tVEMPs) with and without visual feedback. DESIGN tVEMP responses to 95 dB nHL 500-Hz tone bursts were recorded in a longitudinal, repeated measures study where P1 and N1 latencies and amplitudes were measured on three separate occasions from the same individuals. Analysis of variance, intra-class correlations, and limits of repeatability analyses were used to assess tVEMP repeatability and effects of visual feedback. STUDY SAMPLE Fifteen participants (nine women) aged between 18 and 41 years took part. RESULTS Response rates of 63% and 68% were obtained for tVEMPs with eyes open and closed, respectively. When present, tVEMP latencies and amplitudes exhibited fair to good repeatability. Repeatability of tVEMP latencies and amplitudes measured using Bland-Altman methods was poorer with eyes closed. CONCLUSIONS Sound-evoked tVEMP response rates are too low to support their clinical utility at the moment. tVEMP response rate may be improved by refining the balance task to include a force related target. Better tVEMP repeatability with eyes open supports the hypothesis that the response is modulated by visual feedback, and is consistent with studies reporting triceps responses to galvanic stimulation.
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Cunha LCM, Labanca L, Tavares MC, Gonçalves DU. Vestibular evoked myogenic potential (VEMP) with galvanic stimulation in normal subjects. Braz J Otorhinolaryngol 2014; 80:48-53. [PMID: 24626892 PMCID: PMC9443952 DOI: 10.5935/1808-8694.20140011] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2013] [Accepted: 08/30/2013] [Indexed: 11/20/2022] Open
Abstract
Introdução O potencial evocado miogênico vestibular (VEMP) gerado por estimulação galvânica (GVS) reflete uma resposta vestíbulo-espinhal. A resposta obtida no músculo sóleo é bifásica, primeiro com componente de curta latência (CL), em torno de 60 ms, e depois com o de média latência (ML), em torno de 100 ms. O componente de CL associa-se à função otolítica (sáculo e utrículo), e o de ML, aos ductos semicirculares. Objetivo Descrever os valores de referência do VEMP com estimulação galvânica em indivíduos normais. Casuística e método Forma de estudo transversal; o VEMP foi gerado por GVS de 2 mA/400 ms, aplicada bilateralmente, sob frequência de 5–6 ms. Testou-se resposta no músculo sóleo de 13 sujeitos saudáveis, com idade média de 56 anos. Os sujeitos permaneceram de pé, com cabeça girada contralateral ao GVS aplicado na mastoide. Na configuração catodo direito, anodo esquerda, 30 GVS foi aplicado, seguidos de mais 30 com configuração inversa. Os componentes de CL e de ML da resposta vestibular foram analisados. Resultado Os componentes de CL e de ML foram semelhantes em ambas as pernas. O valor médio de CL foi 54 ms, e o de ML, 112 ms. Conclusão Os componentes de CL e de ML do VEMP solear foram replicáveis, sendo medidas úteis de função do trato vestíbulo-espinhal. © 2014 Associação Brasileira de Otorrinolaringologia e Cirurgia Cérvico-Facial. Publicado por Elsevier Editora Ltda. Todos os direitos reservados.
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Affiliation(s)
- Luciana Cristina Matos Cunha
- Universidade Federal de Minas Gerais, Faculdade de Medicina, Belo HorizonteMG, Brasil, Faculdade de Medicina da Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG, Brasil
| | - Ludimila Labanca
- Universidade Federal de Minas Gerais, Faculdade de Medicina, Belo HorizonteMG, Brasil, Faculdade de Medicina da Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG, Brasil
| | - Maurício Campelo Tavares
- Universidade Católica de Pelotas, PelotasRS, Brasil, Universidade Católica de Pelotas, Pelotas, RS, Brasil
| | - Denise Utsch Gonçalves
- Universidade Federal de Minas Gerais, Faculdade de Medicina, Belo HorizonteMG, Brasil, Faculdade de Medicina da Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG, Brasil
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Matos Cunha LC, Campelo Tavares M, Tierra Criollo CJ, Labanca L, Cardoso dos Santos Couto Paz C, Resende Martins H, de Freitas Carneiro-Proietti AB, Utsch Goncalves D. Contribution of Galvanic Vestibular Stimulation for the Diagnosis of HTLV-1-Associated Myelopathy/Tropical Spastic Paraparesis. J Clin Neurol 2013; 9:252-8. [PMID: 24285967 PMCID: PMC3840136 DOI: 10.3988/jcn.2013.9.4.252] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2012] [Revised: 04/04/2013] [Accepted: 04/04/2013] [Indexed: 12/14/2022] Open
Abstract
BACKGROUND AND PURPOSE Galvanic vestibular stimulation (GVS) is a low-cost and safe examination for testing the vestibulospinal pathway. Human T-lymphotropic virus 1 (HTLV-1)-associated myelopathy/tropical spastic paraparesis (HAM/TSP) is a slowly progressive disease that affects the vestibulospinal tract early in its course. This study compared the electromyographic (EMG) responses triggered by GVS of asymptomatic HTLV-1-infected subjects and subjects with HAM/TSP. METHODS Bipolar galvanic stimuli (400 ms and 2 mA) were applied to the mastoid processes of 39 subjects (n=120 stimulations per subject, with 60 from each lower limb). Both the short latency (SL) and medium latency (ML) components of the EMG response were recorded from the soleus muscles of 13 healthy, HTLV-1-negative adults (56±5 years, mean±SD), and 26 individuals infected with HTLV-1, of whom 13 were asymptomatic (56±8 years) and 13 had HAM/TSP (60±6 years). RESULTS The SL and ML EMG components were 55±4 and 112±10 ms, respectively, in the group of healthy subjects, 61±6 and 112±10 ms and in the HTLV-1-asymptomatic group, and 67±8 and 130±3 ms in the HAM/TSP group (p=0.001). The SL component was delayed in 4/13 (31%) of the examinations in the HTLV-1-asymptomatic group, while the ML component was normal in all of them. In the HAM/TSP group, the most common alteration was the absence of waves. CONCLUSIONS A pattern of abnormal vestibular-evoked EMG responses was found in HTLV-1-neurological disease, ranging from delayed latency among asymptomatic carriers to the absence of a response in HAM/TSP. GVS may contribute to the early diagnosis and monitoring of nontraumatic myelopathies.
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Affiliation(s)
| | | | | | - Ludimila Labanca
- Faculty of Medicine, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil
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Guleyupoglu B, Schestatsky P, Edwards D, Fregni F, Bikson M. Classification of methods in transcranial electrical stimulation (tES) and evolving strategy from historical approaches to contemporary innovations. J Neurosci Methods 2013; 219:297-311. [PMID: 23954780 DOI: 10.1016/j.jneumeth.2013.07.016] [Citation(s) in RCA: 119] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2013] [Revised: 07/17/2013] [Accepted: 07/25/2013] [Indexed: 12/28/2022]
Abstract
Transcranial Electrical Stimulation (tES) encompasses all methods of non-invasive current application to the brain used in research and clinical practice. We present the first comprehensive and technical review, explaining the evolution of tES in both terminology and dosage over the past 100 years of research to present day. Current transcranial Pulsed Current Stimulation (tPCS) approaches such as Cranial Electrotherapy Stimulation (CES) descended from Electrosleep (ES) through Cranial Electro-stimulation Therapy (CET), Transcerebral Electrotherapy (TCET), and NeuroElectric Therapy (NET) while others like Transcutaneous Cranial Electrical Stimulation (TCES) descended from Electroanesthesia (EA) through Limoge, and Interferential Stimulation. Prior to a contemporary resurgence in interest, variations of transcranial Direct Current Stimulation were explored intermittently, including Polarizing current, Galvanic Vestibular Stimulation (GVS), and Transcranial Micropolarization. The development of these approaches alongside Electroconvulsive Therapy (ECT) and pharmacological developments are considered. Both the roots and unique features of contemporary approaches such as transcranial Alternating Current Stimulation (tACS) and transcranial Random Noise Stimulation (tRNS) are discussed. Trends and incremental developments in electrode montage and waveform spanning decades are presented leading to the present day. Commercial devices, seminal conferences, and regulatory decisions are noted. We conclude with six rules on how increasing medical and technological sophistication may now be leveraged for broader success and adoption of tES.
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Affiliation(s)
- Berkan Guleyupoglu
- Neural Engineering Laboratory, Department of Biomedical Engineering, The City College of New York of CUNY, New York, NY 10031, USA
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Transmastoid galvanic stimulation does not affect the vergence-mediated gain increase of the human angular vestibulo-ocular reflex. Exp Brain Res 2012; 224:489-99. [PMID: 23150093 DOI: 10.1007/s00221-012-3330-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2012] [Accepted: 10/27/2012] [Indexed: 10/27/2022]
Abstract
Vergence is one of several viewing contexts that require an increase in the angular vestibular-ocular reflex (aVOR) response. A previous monkey study found that the vergence-mediated gain (eye/head velocity) increase of the aVOR was attenuated by 64 % when anodic currents, which preferentially lower the activity of irregularly firing vestibular afferents, were delivered to both labyrinths. We sought to determine whether there was similar evidence implicating a role for irregular afferents in the vergence-mediated gain increase of the human aVOR. Our study is based upon analysis of the aVOR evoked by head rotations, delivered passively while subjects viewed a near (15 cm) or far (124 cm) target and applying galvanic vestibular stimulation (GVS) via surface electrodes. We tested 12 subjects during 2-3 sessions each. Vestibular stimuli consisted of passive whole-body rotations (sinusoids from 0.05-3 Hz and 12-25°/s, and transients with peak ~15°, 50°/s, 500°/s(2)) and head-on-body impulses (peak ~30°, 150°/s, 3,000°/s(2)). GVS was on for 10 s every 20 s. All polarity combinations were tested, with emphasis on uni- and bi-lateral anodic inhibition. The average stimulus current was 5.9 ± 1.6 mA (range: 3-9.5 mA), vergence angle (during near viewing) was 22.6 ± 2.8° and slow-phase eye velocity caused by left anodic current stimulation with head stationary was -3.4 ± 1.1°/s, -0.2 ± 0.6°/s and 2.5 ± 1.4°/s (torsion, vertical, horizontal). No statistically significant GVS effects were observed, suggesting that surface electrode GVS has no effect on the vergence-mediated gain increase of the aVOR at the current levels (~6 mA) tolerated by most humans. We conclude that clinically practical transmastoid GVS does not effectively silence irregular afferents and hypothesize that currents >10 mA are needed to reproduce the monkey results.
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Laube R, Govender S, Colebatch JG. Vestibular-dependent spinal reflexes evoked by brief lateral accelerations of the heads of standing subjects. J Appl Physiol (1985) 2012; 112:1906-14. [DOI: 10.1152/japplphysiol.00007.2012] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
An impulsive acceleration stimulus, previously shown to activate vestibular afferents, was applied to the mastoid. Evoked EMG responses from the soleus muscles in healthy subjects ( n = 10) and patients with bilateral vestibular dysfunction ( n = 3) were recorded and compared with the effects of galvanic stimulation (GVS). Subjects were stimulated while having their eyes closed, head rotated, and while tonically activating their soleus muscles. Rectified EMG responses were recorded from the leg contralateral to the direction of head rotation. Responses were characterized by triphasic potentials that consisted of short-latency (SL), medium-latency (ML), and long-latency (LL) components beginning at (mean ± SD) 54.2 ± 4.8, 88.4 ± 4.7, and 121 ± 7.1 ms, respectively. Mean amplitudes for the optimum stimulus rise times were 9.05 ± 3.44% for the SL interval, 16.70 ± 4.41% for the ML interval, and 9.75 ± 4.89% for the LL interval compared with prestimulus values. Stimulus rise times of 14 and 20 ms evoked the largest ML amplitudes. GVS evoked biphasic responses (SL and ML) with similar latencies. Like GVS, the polarity of the initial interval was determined by the polarity of the stimulus and the evoked EMG response was attenuated when subjects were seated. There was no significant EMG response evoked when subjects were stimulated using 500-Hz vibration or in patients with bilateral vestibular dysfunction. Our study demonstrates that a brief lateral acceleration, likely to activate the utricle, can evoke spinal responses with properties similar to those previously shown for vestibular activation by GVS. The triphasic nature of the responses may allow the nervous system to respond differently to short compared with long-duration linear accelerations, consistent with their differing significance.
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Affiliation(s)
| | - Sendhil Govender
- Neuroscience Research Australia, University of New South Wales, Randwick, Sydney, New South Wales, Australia
| | - James G. Colebatch
- Prince of Wales Clinical School and
- Neuroscience Research Australia, University of New South Wales, Randwick, Sydney, New South Wales, Australia
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Muise SB, Lam CK, Bent LR. Reduced input from foot sole skin through cooling differentially modulates the short latency and medium latency vestibular reflex responses to galvanic vestibular stimulation. Exp Brain Res 2012; 218:63-71. [PMID: 22278107 DOI: 10.1007/s00221-012-3002-2] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2011] [Accepted: 01/07/2012] [Indexed: 11/24/2022]
Abstract
Sensory afferent information from the skin of the foot sole and information from the vestibular system converge within the central nervous system; however, their mode of interaction remains unknown. The purpose of this study was to investigate the effect of reduced cutaneous foot sole information on the ability of the vestibular system to evoke short latency (SL) and medium latency (ML) lower limb muscle reflex responses. Galvanic vestibular stimulation (GVS; bipolar; binaural; 25 ms; 2 mA square-wave pulse) was applied to standing human subjects (four women, eight men, average age 21.1 ± 3.0 years) both before and after cooling the foot soles in 1°C ice water (15 min initially, followed by 5 min between blocks of 200 GVS pulses). Changes in soleus reflex amplitude were examined. Following ice water immersion, there was a 35.16% increase in the size of the ML response in the soleus muscle when expressed as a percentage of pre-stimulus electromyographic (EMG) activity (control 26.48 ± 4.91%; ice 36.16 ± 6.52%) with no change in size of the SL response (control 7.42 ± 1.12%; ice 8.72 ± 1.10%). These results support the previously proposed dissociation of the SL and ML responses with respect to their circuitry and functions. The results also suggest a greater role for cutaneous-vestibular interaction in the modulation of the ML than the SL response and at a location prior to the motoneuron pool.
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Affiliation(s)
- Stephanie B Muise
- Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, ON N1G 2W1, Canada
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Reflex responses of masseter muscles to sound. Clin Neurophysiol 2010; 121:1690-9. [DOI: 10.1016/j.clinph.2009.11.093] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2009] [Revised: 10/19/2009] [Accepted: 11/09/2009] [Indexed: 11/18/2022]
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Mian OS, Dakin CJ, Blouin JS, Fitzpatrick RC, Day BL. Lack of otolith involvement in balance responses evoked by mastoid electrical stimulation. J Physiol 2010; 588:4441-51. [PMID: 20855437 DOI: 10.1113/jphysiol.2010.195222] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Passing current through mastoid electrodes (conventionally termed galvanic vestibular stimulation; GVS) evokes a balance response containing a short- and a medium-latency response. The origins of these two responses are debated. Here we test the hypotheses that they originate from net signals evoked by stimulation of otolith and semi-circular canal afferents, respectively. Based on anatomy and function, we predicted the directions of the stimulus-evoked net head rotation vector from the canals and the linear acceleration net vector from the otoliths. We tested these predictions in healthy adults by obtaining responses with the head in strategic postures to alter the relevance of the signals to the balance system. Cross-covariance between a stochastic waveform of stimulating current and motor output was used to assess the balance responses. Consistent with the canal hypothesis, with the head pitched down the medium-latency EMG response was abolished while the short-latency EMG response was maintained. The results, however, did not support the otolith hypothesis. The direction of the linear acceleration signal from the otoliths was predicted to change substantially when using monaural stimuli compared to binaural stimuli. In contrast, short-latency response direction measured from ground-reaction forces was not altered. It was always directed along the inter-aural axis irrespective of whether the stimulus was applied binaurally or monaurally, whether the head was turned in yaw through 90 deg, whether the head was pitched down through 90 deg, or combinations of these manipulations. We conclude that a net canal signal evoked by GVS contributes to the medium-latency response whilst a net otolith signal does not make a significant contribution to either the short- or medium-latency responses.
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Affiliation(s)
- Omar S Mian
- Sobell Department of Motor Neuroscience and Movement Disorders, University College London Institute of Neurology, Queen Square, London WC1N 3BG, UK.
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Day BL, Marsden JF, Ramsay E, Mian OS, Fitzpatrick RC. Non-linear vector summation of left and right vestibular signals for human balance. J Physiol 2009; 588:671-82. [PMID: 20026614 DOI: 10.1113/jphysiol.2009.181768] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
The left and right vestibular organs always transduce the same signal of head movement, and with natural stimuli can only be activated simultaneously. To investigate how signals from the left and right vestibular organs are integrated to control human balance we electrically modulated the firing of vestibular afferents from each labyrinth independently and measured the resulting balance responses. Stimulation of one side at a time (monaural) showed that individual leg muscles receive equal inputs from the two labyrinths even though a single labyrinth appeared capable of signalling 3-D head motion. To deduce principles of left-right integration, balance responses to simultaneous stimulation of both sides (binaural) were compared with responses to monaural stimuli. The binaural whole-body response direction was compatible with vector summation of the left and right monaural responses. The binaural response magnitude, however, was only 64-74% that predicted by the monaural sum. This probably reflects a central non-linearity between vestibular input and motor output because stimulation of just one labyrinth revealed a power law relationship between stimulus current and response size with exponents 0.56 (force) and 0.51 (displacement). Thus, doubling total signal magnitude either by doubling monaural current or by binaural stimulation produced equivalent responses. We conclude that both labyrinths provide independent estimates of head motion that are summed vectorially and transformed non-linearly into motor output. The former process improves signal-to-noise and reduces artifactual common-mode changes, while the latter enhances responses to small signals, all critical for detecting the small head movements needed to control human balance.
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Affiliation(s)
- Brian L Day
- Sobell Department of Motor Neuroscience and Movement Disorders, UCL Institute of Neurology, Queen Square, London WC1N 3BG, UK.
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Abstract
OBJECTIVE To determine if a sound evoked myogenic potential could be obtained from the triceps with the recording and stimulus parameters routinely used to obtain a vestibular evoked myogenic potential (VEMP) from the sternocleidomastoid. STUDY DESIGN Prospective study of myogenic potentials recorded from the triceps in healthy subjects. We used a monaural acoustic stimulus and measured the unrectified myogenic potential using surface electromyography electrodes, using response-triggered averaging, on the triceps of 18 subjects. SETTING University-affiliated otoneurology clinic. PATIENTS Eighteen healthy adult volunteers (11 women and 7 men), age ranging between 27 and 36 years. MAIN OUTCOME MEASURES Latencies and amplitudes of the first two waves of the evoked response. RESULTS : The P1 latency was 36.83 +/- 8.42 ms (range, 26.34-57.99 ms; 95% confidence interval [CI], 33.53-40.14 ms), the N1 latency was 43.74 +/- 8.80 ms (range, 34.67-66.32 ms; 95% CI, 40.29-47.19 ms), the P1-N1 interlatency was 6.90 +/- 1.23 ms (range, 5.21-9.79 ms; 95% CI, 6.42-7.39 ms), and the P1-N1 interamplitude was 93.23 +/- 51.25 microV (range, 16.33-206.62 microV; 95% CI, 73.14-113.32 V). CONCLUSION A monaural sound stimulus elicits a robust and reproducible surface myogenic potential in triceps muscles.
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Lowrey CR, Bent LR. Modulation of the soleus H-reflex following galvanic vestibular stimulation and cutaneous stimulation in prone human subjects. Muscle Nerve 2009; 40:213-20. [PMID: 19367637 DOI: 10.1002/mus.21275] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Catherine R Lowrey
- Neurophysiology Laboratory, Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario N1G 2W1, Canada
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Abstract
OBJECTIVE To determine if an evoked myogenic potential could be obtained from the gastrocnemius of the leg with similar recording and stimulus parameters to those routinely used to obtain vestibular-evoked myogenic potentials from the sternocleidomastoid (SCM) of the neck. STUDY DESIGN Prospective study in which we recorded evoked myogenic potentials from the gastrocnemius and compared it with the response obtained at the SCM. SETTING University-affiliated hearing clinic. PATIENTS Twelve healthy adult volunteers and 1 patient with bilateral vestibular loss were studied. Ages of the healthy subjects ranged between 18 and 54 years. MAIN OUTCOME MEASURE(S) Myogenic potentials evoked by tone-burst stimuli (95 dB hearing level, 500 Hz) were recorded with surface electrodes over each gastrocnemius and SCM muscle and averaged. Latencies and amplitudes of the responses were measured. RESULTS Responses were obtained in the gastrocnemius, both ipsilateral and contralateral to the acoustic stimulus. The response consisted of 2 biphasic waves (P1-N1 and P2-N2), although not all subjects exhibited both components. The most reliable wave was P2-N2, which was measured ipsilaterally in 81% of the subjects and contralaterally in 68%. Responses were smaller and later than those in the SCM. CONCLUSION An acoustically evoked myogenic potential can be recorded from the leg using the same stimulus that is routinely used to obtain a vestibular-evoked myogenic potential response from the SCM. The presence of this response in the leg ipsilateral and contralateral to the stimulated ear suggests that the response travels via crossed and uncrossed pathways in the spinal cord.
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Ghanim Z, Lamy JC, Lackmy A, Achache V, Roche N, Pénicaud A, Meunier S, Katz R. Effects of galvanic mastoid stimulation in seated human subjects. J Appl Physiol (1985) 2008; 106:893-903. [PMID: 19095754 DOI: 10.1152/japplphysiol.90594.2008] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The vestibular responses evoked by transmastoid galvanic stimulation (GS) in the rectified soleus electromyogram (EMG) in freely standing human subjects disappear when seated. However, a GS-induced facilitation of the soleus monosynaptic (H and tendon jerk) reflex has been described in few experiments in subjects lying prone or seated. This study addresses the issue of whether this reflex facilitation while seated is of vestibulospinal origin. GS-induced responses in the soleus (modulation of the rectified ongoing EMG and of the monosynaptic reflexes) were compared in the same normal subjects while freely standing and sitting with back and head support. The polarity-dependent biphasic responses in the free-standing position were replaced by a non-polarity-dependent twofold facilitation while seated. The effects of GS were hardly detectable in the rectified ongoing voluntary EMG activity, weak for the H reflex, but large and constant for the tendon jerk. They were subject to habituation. Anesthesia of the skin beneath the GS electrodes markedly reduced the reflex facilitation, while a similar, although weaker, facilitation of the tendon jerk was observed when GS was replaced with purely cutaneous stimulation, a tap to the tendon of the sternomastoid muscle, or an auditory click. The stimulation polarity independence of the GS-induced reflex facilitation argues strongly against a vestibular response. However, the vestibular afferent volley, insufficient to produce a vestibular reflex response while seated, could summate with the GS-induced tactile or proprioceptive volley to produce a startle-like response responsible for the reflex facilitation.
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Affiliation(s)
- Z Ghanim
- Université Pierre et Marie Curie-Paris 6, Unité Mixte de Recherche, Paris
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Liechti M, Müller R, Lam T, Curt A. Vestibulospinal responses in motor incomplete spinal cord injury. Clin Neurophysiol 2008; 119:2804-12. [PMID: 18842452 DOI: 10.1016/j.clinph.2008.05.033] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2006] [Revised: 05/13/2008] [Accepted: 05/16/2008] [Indexed: 11/18/2022]
Abstract
OBJECTIVE Postural instability limits ambulatory capacity in patients with spinal cord injury (SCI). Galvanic vestibular stimulation (GVS) was used to investigate the integrity of vestibulospinal pathways and related changes in postural responses in SCI. METHODS Binaural bipolar galvanic stimuli of 400 ms duration and 3 mA intensity were applied in 8 motor incomplete SCI and 8 control subjects who stood facing towards the left. EMG responses were recorded from the right soleus muscle and the trajectory of the centre of pressure (CoP) was measured with a force plate. RESULTS There was no difference in excitability and amplitude of the responses between the groups. However, the latency and duration of the medium latency EMG response and all CoP responses were significantly longer in the SCI group. Additionally, postural stability was reduced in the SCI group, as shown by a greater tendency to fall due to GVS. CONCLUSIONS Despite early EMG responses proving the basic connectivity of the direct vestibulospinal pathways, the delayed GVS responses suggest a vestibulospinal deficit in the SCI subjects. SIGNIFICANCE GVS can be applied in incomplete SCI to supplement the neurological examination by revealing changes in vestibulospinal responses and impairment of postural stability.
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Affiliation(s)
- M Liechti
- Balgrist University Hospital, Spinal Cord Injury Center, Forchstrasse 340, 8008 Zurich, Switzerland
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Son GML, Blouin JS, Inglis JT. Short-duration galvanic vestibular stimulation evokes prolonged balance responses. J Appl Physiol (1985) 2008; 105:1210-7. [PMID: 18669937 DOI: 10.1152/japplphysiol.01398.2006] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The application of galvanic vestibular stimulation (GVS) evokes distinct responses in lower limb muscles involved in the control of balance. The purpose of this study was to investigate the balance and lower limb muscle responses to short-duration GVS and to determine whether these responses are modulated by small changes in center of gravity (CoG) and baseline muscle activity occurring during quiet standing. Twelve subjects stood quietly on a force plate with their feet together and were instructed to look straight ahead. One thousand twenty-four GVS stimuli (4 mA, 20-ms pulses) were delivered bilaterally to the mastoid processes in a bipolar, binaural configuration. Bilateral surface electromyography (EMG) from soleus (Sol) and tibialis anterior (TA) and ground reaction forces were recorded. EMG and force responses were trigger averaged at the onset of the GVS pulse. Short-duration GVS applied during quiet standing with the head facing forward evoked characteristic balance responses and biphasic modulation of all muscles with the same polarity for ipsilateral Sol and TA. The amplitude of the GVS-evoked muscle responses was modulated by both the estimated position of the subject's CoG and the background activation of the recorded muscle. Muscle-dependent modulations of the GVS-evoked muscle responses were observed: the Sol responses decreased, while the TA responses increased when the CoG position shifted toward the heels. The well-defined balance responses evoked by short-duration GVS are important to acknowledge when studying the vestibulo-motor responses in healthy subjects and patient populations.
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Schlosser HG, Guldin W, Fritzsche D, Clarke AH. Transcranial Doppler ultrasound during galvanic labyrinth polarization depicts central vestibular processing, demonstrating bilateral vestibular projection. Eur J Neurosci 2008; 28:372-8. [DOI: 10.1111/j.1460-9568.2008.06331.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Deriu F, Ortu E, Capobianco S, Giaconi E, Melis F, Aiello E, Rothwell JC, Tolu E. Origin of sound-evoked EMG responses in human masseter muscles. J Physiol 2007; 580:195-209. [PMID: 17234698 PMCID: PMC2075422 DOI: 10.1113/jphysiol.2006.123240] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Sound is a natural stimulus for both cochlear and saccular receptors. At high intensities it evokes in active masseter muscles of healthy subjects two overlapping reflexes: p11/n15 and p16/n21 waves, whose origin has not yet been demonstrated. Our purpose was to test which receptor in the inner ear is responsible for these reflexes. We compared masseter EMG responses induced in normal subjects (n = 9) by loud clicks (70-100 dB normal hearing level (NHL), 0.1 ms, 3 Hz) to those evoked in subjects with a selective lesion of the cochlea (n = 5), of the vestibule (n = 1) or with mixed cochlear-vestibular failure (n = 5). In controls, 100 dB clicks induced bilaterally, in the unrectified mean EMG (unrEMG), a clear p11 wave followed by a less clear n15 wave and a subsequent n21 wave. Lowering the intensity to 70 dB clicks abolished the p11/n15 wave, while a p16 wave appeared. Rectified mean EMG (rectEMG) showed, at all intensities, an inhibitory deflection corresponding to the p16/n21 wave in the unrEMG. Compared to controls, all deaf subjects had a normal p11 wave, together with more prominent n15 wave; however, the p16/n21 waves, and their corresponding inhibition in the rectEMG, were absent. The vestibular patient had bilaterally clear p11 waves only when 100 dB clicks were delivered bilaterally or to the unaffected ear. Stimulation of the affected ear induced only p16/n21 waves. Data from mixed patients were consistent with those of deaf and vestibular patients. We conclude that click-induced masseter p11/n15 waves are vestibular dependent, while p16/n21 waves depend on cochlear integrity.
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Affiliation(s)
- Franca Deriu
- Department of Biomedical Sciences, Section of Human Physiology and Bioengineering, Viale San Pietro 43/b, 07100--Sassari, Italy.
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Bacsi AM, Colebatch JG. Evidence for reflex and perceptual vestibular contributions to postural control. Exp Brain Res 2005; 160:22-8. [PMID: 15322784 DOI: 10.1007/s00221-004-1982-2] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Vestibular signals are known to have an important role in stance under specific conditions. Potentially these effects could be modulated by vestibular reflexes or by voluntary responses to perceived vestibular signals. Our preliminary aim was to confirm that vestibulospinal reflexes change in parallel with sway under different postural conditions, and then to determine whether any relationship was present between these reflexes and body sway within fixed postural conditions. Sixteen subjects (eight male, eight female) were tested in conditions assessing the effects of vision (eyes open or closed), support surface (firm or compliant), external support (with or without) and stance width (feet apart or together). Sway (centre of pressure) in the anteroposterior (AP) and mediolateral planes was measured using a force platform. A subgroup of 11 subjects (five male, six female) underwent testing to measure short (SL) and medium latency (ML) reflexes from soleus. Bipolar, transmastoid galvanic stimulation (1 mA, 200 ms) was administered while subjects stood in the most unstable of our conditions (eyes closed, compliant surface and feet together). In the final part, to assess possible perceptual contributions to body sway, short duration AP sway levels were measured and expressed in angular terms (sway in mrad, velocity in mrad s(-1)) in the 11 subjects for both our baseline (eyes open, firm surface and feet apart) and most unstable conditions. Average sway levels increased more than seven-fold between conditions and had significant, positive correlations with reported changes in mean vestibulospinal reflexes under similar conditions (overall r = 0.75, P < 0.001). However, the SL reflex for the subgroup of 11 subjects had a significant negative correlation (r = -0.71; P = 0.014) with the degree of AP sway in the condition with maximum reliance on vestibular inputs (eyes closed, compliant surface, and feet together). Under baseline conditions, 5/125 (4%) of the short-term AP sway displacements were above the threshold previously reported for the detection of imposed sway. In the unstable condition, when sway was increased, 43/138 (31%) of the short-term AP sway movements were above the threshold for perception of imposed body sway based on vestibular signals. Our results confirm that vestibulospinal reflexes appear to be acutely facilitated as body sway increases. For the most unstable condition, when non-vestibular information was absent or attenuated, subjects with larger SL reflexes had less AP sway, suggesting that the SL reflex acted to attenuate sway. Under the same condition, short duration sway levels increased such that 31% were above the previously published threshold for detection using vestibular afferents. We conclude that both vestibular reflexes and perceptual signals appear to have a specific role in the maintenance of upright stance, under conditions in which other sources of postural information are attenuated or absent.
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Affiliation(s)
- Ann M Bacsi
- Institute of Neurological Sciences and UNSW Clinical School, Prince of Wales Hospital, Randwick, 2031 Sydney, NSW, Australia
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Abstract
OBJECTIVES To examine vestibular control of balance in those who recovered the ability to stand after middle cerebral artery (MCA) stroke. METHODS Sixteen patients with MCA stroke were compared with 10 age matched controls. Two additional patients were studied with isolated corticospinal tract lesions, one each at the level of the pons and medulla. Vestibular evoked postural responses were obtained using galvanic vestibular stimulation (GVS) while patients stood with their eyes closed and head facing forwards, equally loading both legs. The GVS response was characterised by measuring the amplitude of the stimulus evoked lateral forces acting through each leg and the lateral displacement of the axial skeleton. RESULTS Lateral displacement and net lateral force following GVS were significantly larger after stroke. Unlike controls, the lateral forces in the stroke group were asymmetrical, being enhanced on the side of the non-paretic limb and small on the side of the paretic limb. The degree of GVS evoked asymmetry correlated with corticospinal damage assessed using transcranial magnetic stimulation. A similar asymmetrical response was seen in the patient with the pontine lesion but not the patient with the medullary lesion. CONCLUSIONS MCA stroke may disrupt corticobulbar projections to brainstem output pathways involved in vestibular control of balance. These projections are either collaterals of the corticospinal tract or lie close to that tract and terminate in the pons/upper medulla. This hypothesis accounts for the association between corticospinal tract damage and GVS response asymmetry, and the lack of GVS evoked asymmetry with corticospinal lesions below the rostral medulla.
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Affiliation(s)
- J F Marsden
- MRC Human Movement Group, Sobell Department of Movement Disorders and Motor Neuroscience, Institute of Neurology, Queen Square, London WCIN 3BG, UK.
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Deriu F, Tolu E, Rothwell JC. A Sound-Evoked Vestibulomasseteric Reflex in Healthy Humans. J Neurophysiol 2005; 93:2739-51. [PMID: 15601734 DOI: 10.1152/jn.01005.2004] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Averaged responses to loud clicks were recorded in the unrectified and rectified masseter electromyogram (EMG) of 18 healthy subjects. Unilateral clicks (0.1 ms, 3 Hz, 70–100 dB NHL), delivered during a steady masseter contraction, evoked bilateral responses that appeared to consist of 2 components on the basis of threshold, latency, and their appearance in rectified EMG. The lowest threshold response appeared as a p16 wave (onset 11–13 ms) in the unrectified EMG and corresponded with a 10- to 12-ms period of inhibition in the rectified EMG. Higher-intensity clicks recruited an earlier p11 response in the unrectified EMG (onset 7.0–9.2 ms) that sometimes appeared as an initial increase in the rectified EMG before suppression. The amplitude of the p11 wave scaled with background EMG level and was asymmetrically modulated by 30° tilt of the whole body. The threshold of the early p11/n15 wave in masseter was the same as the threshold for click-induced vestibulocollic reflexes. Single motor unit recordings demonstrated that responses in masseters corresponded to a silent period in unit firing that began earlier and lasted longer at 100 dB than at 80 dB. We propose that loud clicks induce 2 partially overlapping short-latency reflexes in masseter muscle EMG: a p11/n15 response, which we suggest is of vestibular origin, and a p16/n21 response, which we suggest is equivalent to the previously described jaw–acoustic reflex.
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Affiliation(s)
- Franca Deriu
- Department of Biomedical Sciences, Section of Human Physiology and Bioengineering, University of Sassari, Italy.
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Dependence of the Magnitude of Postural Reactions in Humans on the Strength of Unilateral Galvanic Anodal and Cathodal Vestibular Stimulations. NEUROPHYSIOLOGY+ 2005. [DOI: 10.1007/s11062-005-0058-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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31
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Abstract
Galvanic vestibular stimulation (GVS) is a simple, safe, and specific way to elicit vestibular reflexes. Yet, despite a long history, it has only recently found popularity as a research tool and is rarely used clinically. The obstacle to advancing and exploiting GVS is that we cannot interpret the evoked responses with certainty because we do not understand how the stimulus acts as an input to the system. This paper examines the electrophysiology and anatomy of the vestibular organs and the effects of GVS on human balance control and develops a model that explains the observed balance responses. These responses are large and highly organized over all body segments and adapt to postural and balance requirements. To achieve this, neurons in the vestibular nuclei receive convergent signals from all vestibular receptors and somatosensory and cortical inputs. GVS sway responses are affected by other sources of information about balance but can appear as the sum of otolithic and semicircular canal responses. Electrophysiological studies showing similar activation of primary afferents from the otolith organs and canals and their convergence in the vestibular nuclei support this. On the basis of the morphology of the cristae and the alignment of the semicircular canals in the skull, rotational vectors calculated for every mode of GVS agree with the observed sway. However, vector summation of signals from all utricular afferents does not explain the observed sway. Thus we propose the hypothesis that the otolithic component of the balance response originates from only the pars medialis of the utricular macula.
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Affiliation(s)
- Richard C Fitzpatrick
- Prince of Wales Medical Research Institute, Easy St., Randwick, Sydney, NSW 2031, Australia.
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32
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Jankelowitz SK, Colebatch JG. Galvanic evoked vestibulospinal and vestibulocollic reflexes in stroke. Clin Neurophysiol 2004; 115:1796-801. [PMID: 15261858 DOI: 10.1016/j.clinph.2004.03.021] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/24/2004] [Indexed: 11/25/2022]
Abstract
OBJECTIVE Following stroke, the startle reflex, mediated via the reticulospinal tract, is often facilitated. Vestibulospinal reflexes are another bulbospinal reflex, abnormalities of which may contribute to impaired body posture and stance following stroke. We recorded galvanic evoked vestibulospinal and vestibulocollic reflexes to assess whether these showed similar changes to those for startle following stroke affecting the pons and above. METHODS Twenty-four stroke subjects (aged 40-82) were studied in the vestibulospinal part of the study, 21 stroke subjects (aged 40-81 years) were studied in the vestibulocollic part, including 18 studied in both. Transmastoid galvanic (DC) current was used to stimulate the vestibular nerve. Vestibulocollic responses were recorded from the sternocleidomastoid muscles and vestibulospinal responses from over soleus in standing subjects. RESULTS Vestibulocollic reflex amplitudes and latencies showed no significant differences between the two sides. Similarly short latency (SL) and medium latency (ML) vestibulospinal reflexes did not differ significantly in frequency, latency or amplitude between the affected and unaffected legs. CONCLUSIONS Vestibular reflexes are not facilitated by stroke at or above the pontine level. The exaggeration of startle by stroke may be specific to this reflex.
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Affiliation(s)
- S K Jankelowitz
- Department of Neurology, Institute of Neurological Sciences, Prince of Wales Hospital, Sydney 2031, Australia
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33
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Kennedy PM, Cresswell AG, Chua R, Inglis JT. Galvanic vestibular stimulation alters the onset of motor unit discharge. Muscle Nerve 2004; 30:188-94. [PMID: 15266634 DOI: 10.1002/mus.20074] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
We have previously shown that galvanic vestibular stimulation (GVS) can modulate the amplitude of the passive soleus H-reflex. This study examined whether the response resulted from a general change in excitability of the motoneuron pool or a specific modulation of individual motor units (MUs). Subjects performed slow isometric plantarflexor actions in a prone lying and kneeling position until the discharge of a single gastrocnemius MU was detected. During randomly selected trials, a 1-mA bipolar, binaural galvanic stimulus was triggered just prior to the start of plantarflexor activity. With the knee extended and the medial gastrocnemius (MG) at a long muscle length, GVS did not have an effect on MU activity. However, when the knee was flexed and the MG muscle was shortened, GVS significantly modified the onset of activation and the initial firing frequency of MUs. This may reflect a change in the gain of the presynaptic inhibitory mechanisms that act on the motoneuron pool once a muscle reaches a shortened, nonoptimal force-producing length. Thus, GVS may provide an important research tool for activating descending vestibulospinal pathways that act on lower-limb motoneurons and may be applied to test the integrity of the spinal cord.
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Affiliation(s)
- Paul M Kennedy
- School of Human Kinetics, The University of British Columbia, 210-6081 University Boulevard, Vancouver, British Columbia V6T 1Z1, Canada
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34
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Kennedy PM, Cresswell AG, Chua R, Inglis JT. Vestibulospinal influences on lower limb motoneurons. Can J Physiol Pharmacol 2004; 82:675-81. [PMID: 15523524 DOI: 10.1139/y04-080] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Galvanic vestibular stimulation (GVS) is a research tool used to activate the vestibular system in human subjects. When a low-intensity stimulus (1–4 mA) is delivered percutaneously to the vestibular nerve, a transient electromyographic response is observed a short time later in lower limb muscles. Typically, galvanically evoked responses are present when the test muscle is actively engaged in controlling standing balance. However, there is evidence to suggest that GVS may be able to modulate the activity of lower limb muscles when subjects are not in a free-standing situation. The purpose of this review is to examine 2 studies from our laboratory that examined the effects of GVS on the lower limb motoneuron pool. For instance, a monopolar monaural galvanic stimulus modified the amplitude of the ipsilateral soleus H-reflex. Furthermore, bipolar binaural GVS significantly altered the onset of activation and the initial firing frequency of gastrocnemius motor units. The following paper examines the effects of GVS on muscles that are not being used to maintain balance. We propose that GVS is modulating motor output by influencing the activity of presynaptic inhibitory mechanisms that act on the motoneuron pool.Key words: galvanic vestibular stimulation, h-reflex, motor unit, vestibulospinal, human.
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Affiliation(s)
- Paul M Kennedy
- School of Human Kinetics, University of British Columbia, Vancouver, BC V6T 1Z1, Canada.
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35
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Monobe H, Murofushi T. Vestibular testing by electrical stimulation in patients with unilateral vestibular deafferentation: galvanic evoked myogenic responses testing versus galvanic body sway testing. Clin Neurophysiol 2004; 115:807-11. [PMID: 15003760 DOI: 10.1016/j.clinph.2003.11.035] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/13/2003] [Indexed: 10/26/2022]
Abstract
OBJECTIVE To investigate the agreement of a lesion site as indicated by two different vestibular tests with electrical stimulation, galvanic body sway testing (GBST) and galvanic evoked myogenic responses (galvanic vestibular evoked myogenic potential; galvanic VEMP) testing, in patients with unilateral vestibular deafferentation. METHODS Nineteen patients with unilateral vestibular deafferentation were studied, and the criteria for patient selection were as follows: (1) absence of a caloric response to ice water on the affected side in a supine position, and (2) absence of VEMP to 95 dBnHL clicks on the affected side. We assessed the postural response of the subjects to long duration galvanic stimulation (1 mA, 5 s) by measuring the lateral displacement at the center of foot pressure with a cathode electrode on the forehead, and an anode electrode on the mastoid (GBST). We also recorded the electromyographic (EMG) activities of the sternocleidomastoid muscle (SCM) to short duration galvanic stimulation (3 mA, 1 ms) (galvanic VEMP) with a cathode electrode on the mastoid, and an anode electrode on the forehead. RESULTS In 18 of the 19 patients, the lesion site indicated by GBST was identical to that indicated by galvanic VEMP. Fourteen patients had abnormal results in both tests while 4 patients had normal results in both tests. One patient with acoustic neuroma had normal results in GBST but abnormal results in galvanic VEMP. CONCLUSIONS These results suggest that electrical stimulation in these two tests stimulates the same area of the peripheral vestibular afferent system, although the duration of stimulation was different, and that the estimate of the lesion site indicated by these tests in patients with complete or nearly complete unilateral vestibular damages is reliable. SIGNIFICANCE These results suggest that short-duration galvanic stimulation as well as long-duration galvanic stimulation stimulates the vestibular system at the same level.
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Affiliation(s)
- Hiroko Monobe
- Department of Otolaryngology, Faculty of Medicine, University of Tokyo, 7-3-1 Hongo Bunkyo-ku, Tokyo 113-8655, Japan
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36
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Deriu F, Tolu E, Rothwell JC. A short latency vestibulomasseteric reflex evoked by electrical stimulation over the mastoid in healthy humans. J Physiol 2003; 553:267-79. [PMID: 12949229 PMCID: PMC2343496 DOI: 10.1113/jphysiol.2003.047274] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
We describe EMG responses recorded in active masseter muscles following unilateral and bilateral electrical vestibular stimulation (EVS, current pulses of 5 mA intensity, 2 ms duration, 3 Hz frequency). Averaged responses in unrectified masseter EMG induced by unilateral EVS were examined in 16 healthy subjects; effects induced by bilateral (transmastoid) stimulation were studied in 10 subjects. Results showed that unilateral as well as bilateral EVS induces bilaterally a clear biphasic response (onset latency ranging from 7.2 to 8.8 ms), that is of equal amplitude and latency contra- and ipsilateral to the stimulation site. In all subjects, unilateral cathodal stimulation induced a positive-negative response termed p11/n15 according to its mean peak latency; the anodal stimulation induced a response of opposite polarity (n11/p15) in 11/16 subjects. Cathodal responses were significantly larger than anodal responses. Bilateral stimulation induced a p11/n15 response significantly larger than that induced by the unilateral cathodal stimulation. Recordings from single motor units showed that responses to cathodal stimulation corresponded to a brief (2-4 ms) silent period in motor unit discharge rate. The magnitude of EVS-induced masseter response was linearly related to current intensity and scaled with the mean level of EMG activity. The size of the p11/n15 response was asymmetrically modulated when subjects were tilted on both sides; in contrast head rotation did not exert any influence. Control experiments excluded a possible role of cutaneous receptors in generating the masseter response. We conclude that transmastoid electrical stimulation evokes vestibulomasseteric reflexes in healthy humans at latencies consistent with a di-trisynaptic pathway.
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Affiliation(s)
- Franca Deriu
- Department of Biomedical Sciences, Section of Human Physiology and Bioengineering, University of Sassari, Sassari, Italy.
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Latt LD, Sparto PJ, Furman JM, Redfern MS. The steady-state postural response to continuous sinusoidal galvanic vestibular stimulation. Gait Posture 2003; 18:64-72. [PMID: 14654209 DOI: 10.1016/s0966-6362(02)00195-9] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Galvanic vestibular stimulation (GVS) applied between the mastoids during quiet standing elicits postural sway. The aim of this study was to characterize the postural sway response to continuous sinusoidal GVS across various stimulus frequencies and amplitudes. Binaural bipolar sinusoidal GVS was applied to the skin overlying the mastoid processes of 10 subjects while they stood on a force plate with eyes closed. The position of the center of pressure (COP) at the feet was recorded from a forceplate, while the head displacement was measured with a magnetic position tracking system. The stimulus conditions included four frequencies (0.1, 0.25, 0.45, and 1.1 Hz) and five peak amplitudes (0.05, 0.1, 0.25, 0.5, and 1.0 mA). Each subject experienced one trial at each amplitude-frequency pair. Additionally, each subject underwent three trials in which a dual-frequency stimulus (0.1 plus 0.45 Hz at a peak of 0.5 mA each) was presented. The stimuli elicited sway in the frontal plane in all subjects, as evidenced by changes in the displacement of the COP and head. Sway magnitude decreased with increasing stimulus frequency and increased with increasing stimulus amplitude. However, the response magnitude saturated at higher stimulus amplitudes. Phase lag increased with increasing stimulus frequency. The response to the dual-frequency stimulus was reduced at 0.1 Hz and nearly equal at 0.45 Hz in comparison with the single-frequency responses. This study suggests that the postural sway response is nonlinear due to saturation and violation of the principle of superposition.
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Affiliation(s)
- L D Latt
- Department of Otolaryngology, University of Pittsburgh, Pittsburgh, PA, USA
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Watson SRD, Welgampola MS, Colebatch JG. EMG responses evoked by the termination of galvanic (DC) vestibular stimulation: 'off-responses'. Clin Neurophysiol 2003; 114:1456-61. [PMID: 12888028 DOI: 10.1016/s1388-2457(03)00121-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
OBJECTIVE Vestibular responses in soleus electromyography (EMG) evoked by the sudden onset of galvanic (DC) stimulation ('on-responses') have been described in detail previously. The aim of the present study was to describe responses in soleus triggered by the termination of galvanic stimulation ('off-responses'). METHODS In 10 healthy human subjects, we studied responses to transmastoid (bilateral) stimuli of 200 ms and 2 s average duration and 3 or 4 mA intensity. We obtained both on- and off-responses using the same raw data. EMG activity was recorded onto tape while current pulses of systematically varying duration were delivered. Averaged on-responses were obtained by triggering from the beginning of the current pulses. Averaged off-responses were obtained by triggering from the termination of the current pulses. RESULTS Short-latency (SL) and medium latency (ML) off-responses were both obtained in all but one study. The SL and the ML components of the off-responses were present and had similar latencies and amplitudes, but opposite excitability, to the on-responses obtained with the same stimuli. CONCLUSIONS Off-responses to galvanic vestibular stimulation can be recorded from soleus EMG. Our findings imply that vestibular SL and ML reflex responses in the legs are dependent on the change in the rate of vestibular nerve discharge, not its absolute level. Both on- and off-responses have properties appropriate to a role in maintaining body stability.
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Affiliation(s)
- S R D Watson
- Institute of Neurological Sciences, Sydney, NSW, Australia
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Bacsi AM, Colebatch JG. Anodal vestibular stimulation does not suppress vestibular reflexes in human subjects. Exp Brain Res 2003; 150:525-8. [PMID: 12739094 DOI: 10.1007/s00221-003-1489-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2003] [Accepted: 04/03/2003] [Indexed: 11/28/2022]
Abstract
Anodal current applied to the vestibular apparatus has previously been found to inhibit discharge from irregular vestibular afferents in squirrel monkeys. We wished to investigate whether anodal currents applied over the mastoid processes of human subjects would significantly reduce ongoing vestibular activity and thereby the size of galvanic-evoked vestibulospinal reflexes, measured by soleus electromyogram. Nine subjects were tested, of whom six subjects (five females, one male) provided data for the final analysis. Tonic anodal current was applied over one mastoid at 0 (baseline), 2, 4, 6 and 8 mA. The cathode was placed at C7. Superimposed on each intensity of tonic current were separate, short anodal currents of 4 mA, duration 20 ms, presented as 128 stimuli to the same side, and used to test vestibular responsiveness. These trials were then repeated with the anode overlying the contralateral mastoid. Short latency (SL) and medium latency (ML) reflexes were measured from the right soleus muscle. All six subjects used in the final analysis had readily identifiable reflexes to all stimuli. One-way ANOVA revealed no significant difference in the magnitude of the SL ( P=0.99) or ML ( P=0.96) components of the vestibulospinal reflexes across the group. Despite surface anodal currents of up to 8 mA, there was no consistent effect on the size of galvanic-evoked vestibulospinal reflexes. As 8 mA is close to the maximum intensity tolerated by volunteer subjects, our results indicate that anodal current applied over the mastoids is unlikely to be a useful means of suppressing vestibular function in human subjects.
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Affiliation(s)
- Ann M Bacsi
- Institute of Neurological Sciences and UNSW Clinical School, Prince of Wales Hospital, Randwick, NSW 2031, Sydney, Australia
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Bacsi AM, Watson SRD, Colebatch JG. Galvanic and acoustic vestibular stimulation activate different populations of vestibular afferents. Clin Neurophysiol 2003; 114:359-65. [PMID: 12559245 DOI: 10.1016/s1388-2457(02)00376-0] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
OBJECTIVE To deduce whether similar or distinct populations of vestibular afferents are activated by acoustic and galvanic vestibular stimulation by comparing the effectiveness of 'matched' stimuli in eliciting vestibulospinal reflexes. METHODS Twelve subjects (5 men, 7 women) underwent individual 'matching' of 2 ms tone burst and galvanic stimuli, using vestibulocollic reflexes so that corrected reflex amplitudes to tone burst and galvanic stimuli were within 10% of each other. These same intensities were then administered using 20 ms durations to determine whether they were equally effective in evoking vestibulospinal responses. RESULTS Corrected reflex amplitudes for vestibulocollic responses to tone burst and galvanic stimulation were not significantly different for the right (P=0.45) or left (P=0.68) sides. All subjects had vestibulospinal responses to galvanic stimulation (average intensity 4.0 mA for both sides). The short latency (SL) and medium latency (ML) components of the vestibulospinal reflexes were larger after galvanic compared to tone burst stimulation in 11 of 12 subjects (P<0.01). CONCLUSIONS Despite evoking equal-sized vestibulocollic reflexes, there was a clear dissociation between the magnitude of tone burst and galvanic-induced vestibulospinal reflexes. Galvanic stimulation evoked SL and ML reflexes in all subjects. Tone burst stimuli evoked only small SL reflexes and, in most cases, no ML reflexes. Acoustically-evoked vestibulocollic reflexes are likely to be due to saccular excitation. The limited effectiveness of longer tone burst stimuli to evoke ML vestibulospinal reflexes suggests that saccular afferents have, at most, only a minor role in the production of these reflexes. We conclude that galvanic stimulation is more effective in eliciting vestibulospinal reflexes than tone burst stimulation, and that the two methods activate different populations of vestibular afferents.
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Affiliation(s)
- Ann M Bacsi
- Institute of Neurological Sciences and UNSW Clinical School, Prince of Wales Hospital, Randwick, Sydney, NSW 2031, Australia
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Ali AS, Rowen KA, Iles JF. Vestibular actions on back and lower limb muscles during postural tasks in man. J Physiol 2003; 546:615-24. [PMID: 12527747 PMCID: PMC2342524 DOI: 10.1113/jphysiol.2002.030031] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
The vestibular system was activated by galvanic electrical stimulation in 19 normal subjects. With the head turned to one side so that the stimulating anode was on the posterior mastoid process, stimulation caused standing subjects to sway backwards in the sagittal plane. Electromyography showed bilateral activation of erector spinae, gluteus maximus, biceps femoris, soleus and intrinsic foot (toe flexor) muscles. When head direction or electrode polarity was reversed so that the anode was anterior, all those muscles became less active and the subjects swayed forwards. With the head facing forward, stimulation caused sideways sway in the coronal plane, towards the anode, with excitation of the erector spinae on the anode side and reduced activity on the cathode side. The limb muscles were activated on the side opposite the anode and showed complex responses on the anode side. Responses were detectable in the erectores spinae muscles in sitting subjects. No responses in limb muscles were detected in the sitting posture. Subject responses in erector spinae recorded at L3/L4 had latencies from 59 to 110 ms, using a 2 mA stimulus. Latencies in lower limb muscles were longer. The results suggest a role for the vestibular system and descending brain stem motor pathways to the erectores spinae muscles in the control of postural orientation of the back when sitting and standing. The conduction velocity in the motor pathway was estimated to be 13 +/- 10 m s(-1) (mean +/- S.D., n = 12 subjects).
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Affiliation(s)
- Alima S Ali
- Department of Zoology, University of Oxford, South Parks Road, Oxford OX1 3PS, UK
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Kennedy PM, Inglis JT. Interaction effects of galvanic vestibular stimulation and head position on the soleus H reflex in humans. Clin Neurophysiol 2002; 113:1709-14. [PMID: 12417223 DOI: 10.1016/s1388-2457(02)00238-9] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
OBJECTIVES The objective of this study is to measure the influence of galvanic vestibular stimulation and head-on-body alignment on the soleus H-reflex in prone human subjects. METHODS We studied changes in the amplitude of the right soleus H-reflex to monopolar monaural galvanic stimulation in 10 healthy prone lying subjects. Trials were randomly administered according to head position (left or right) and stimulus polarity (anode or cathode). We also investigated the influence of the conditioning stimuli by examining the amplitude of the H-reflex based on head position without galvanic stimulation. A one-way and two-way repeated measures analysis of variance were used to compare the mean amplitudes of the test and conditioned H-reflexes. RESULTS The greatest facilitation was observed when the head was turned to the left and coupled with cathodal stimulation. The largest inhibitory effect was found when the head was turned to the right and paired with anodal stimulation. However, when head left was paired with anodal stimulation or head right was coupled with cathodal stimulation, only minimal changes in amplitude were observed. CONCLUSIONS The results demonstrate that there is an interaction between head position and galvanic stimulus polarity when measuring the excitability of the soleus motoneuron pool in prone lying subjects.
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Affiliation(s)
- Paul M Kennedy
- School of Human Kinetics, The University of British Columbia, Vancouver, BC, Canada
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Abstract
It is generally accepted that human bipedal upright stance is achieved by feedback mechanisms that generate an appropriate corrective torque based on body-sway motion detected primarily by visual, vestibular, and proprioceptive sensory systems. Because orientation information from the various senses is not always available (eyes closed) or accurate (compliant support surface), the postural control system must somehow adjust to maintain stance in a wide variety of environmental conditions. This is the sensorimotor integration problem that we investigated by evoking anterior-posterior (AP) body sway using pseudorandom rotation of the visual surround and/or support surface (amplitudes 0.5-8 degrees ) in both normal subjects and subjects with severe bilateral vestibular loss (VL). AP rotation of body center-of-mass (COM) was measured in response to six conditions offering different combinations of available sensory information. Stimulus-response data were analyzed using spectral analysis to compute transfer functions and coherence functions over a frequency range from 0.017 to 2.23 Hz. Stimulus-response data were quite linear for any given condition and amplitude. However, overall behavior in normal subjects was nonlinear because gain decreased and phase functions sometimes changed with increasing stimulus amplitude. "Sensory channel reweighting" could account for this nonlinear behavior with subjects showing increasing reliance on vestibular cues as stimulus amplitudes increased. VL subjects could not perform this reweighting, and their stimulus-response behavior remained quite linear. Transfer function curve fits based on a simple feedback control model provided estimates of postural stiffness, damping, and feedback time delay. There were only small changes in these parameters with increasing visual stimulus amplitude. However, stiffness increased as much as 60% with increasing support surface amplitude. To maintain postural stability and avoid resonant behavior, an increase in stiffness should be accompanied by a corresponding increase in damping. Increased damping was achieved primarily by decreasing the apparent time delay of feedback control rather than by changing the damping coefficient (i.e., corrective torque related to body-sway velocity). In normal subjects, stiffness and damping were highly correlated with body mass and moment of inertia, with stiffness always about 1/3 larger than necessary to resist the destabilizing torque due to gravity. The stiffness parameter in some VL subjects was larger compared with normal subjects, suggesting that they may use increased stiffness to help compensate for their loss. Overall results show that the simple act of standing quietly depends on a remarkably complex sensorimotor control system.
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Affiliation(s)
- R J Peterka
- Neurological Sciences Institute, Oregon Health & Science University, Portland, Oregon 97006, USA.
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Rosengren SM, Colebatch JG. Differential effect of current rise time on short and medium latency vestibulospinal reflexes. Clin Neurophysiol 2002; 113:1265-72. [PMID: 12140006 DOI: 10.1016/s1388-2457(02)00121-9] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
OBJECTIVES To investigate the effect of varying current rise time on galvanic-evoked short (SL) and medium (ML) latency vestibulospinal reflexes. METHODS We recorded the soleus EMG of standing subjects in response to 3 mA direct current transmastoid stimulation with a series of current ramps with rise times of 0-300 ms. RESULTS Longer current rise times significantly delayed the onset of both SL (P<<0.001) and ML (P<<0.001) vestibulospinal responses, by approximately 20 and 39 ms, respectively. The SL response amplitude was reduced with increasing rise time (P<<0.001), whereas the ML response amplitude was relatively unaffected by stimulus rise time. With very slow rise times a prolonged ML response alone was evoked. CONCLUSIONS Both SL and ML reflexes can be evoked by changes in vestibular activity produced by transmastoid galvanic stimulation with a ramp onset. We found a differential effect of current rise time on SL and ML vestibulospinal reflexes, suggesting different potential functional roles for the two reflexes. SL reflexes can participate in the response to abrupt disturbances only. ML reflexes are evoked by both fast and slow changes in vestibular discharge and may be particularly effective for slowly-changing disturbances.
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Affiliation(s)
- S M Rosengren
- Institute of Neurological Sciences and Clinical School, The Prince of Wales Hospital, Randwick, Australia
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Andersson G, Magnusson M. Neck vibration causes short-latency electromyographic activation of lower leg muscles in postural reactions of the standing human. Acta Otolaryngol 2002; 122:284-8. [PMID: 12030575 DOI: 10.1080/000164802753648169] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
To study how quickly cervical proprioceptive information induced muscular responses in the lower leg to control posture in the standing human we investigated lower leg muscle electromyography and force-plate data from 10 healthy normal subjects, when perturbed by posterior neck muscle vibration. At the onset of vibration the tibialis anterior muscle was activated at latencies of 70-100 ms whilst the triceps surae muscle was inhibited at the same latencies. At offset the opposite pattern was observed. These findings suggest that a short-latency integrative system, rather than a direct reflex, mediates the cervical influence on posture. The short latencies also imply that activation of postural muscles in response to vibration towards the neck muscles occurs faster than would be expected if it was caused only by a perceptive illusion of movement.
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Affiliation(s)
- G Andersson
- Department of Clinical Neurophysiology, Lund University Hospital, Sweden
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Murofushi T, Takegoshi H, Ohki M, Ozeki H. Galvanic-evoked myogenic responses in patients with an absence of click-evoked vestibulo-collic reflexes. Clin Neurophysiol 2002; 113:305-9. [PMID: 11856636 DOI: 10.1016/s1388-2457(01)00738-6] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
OBJECTIVES To show that galvanic-evoked responses on the sternocleidomastoid muscle (SCM) are useful for differentiating labyrinthine lesions from retro-labyrinthine lesions in patients with an absence of click-evoked vestibulo-collic reflexes. METHODS We studied the average responses in the unrectified electromyographic (EMG) activities of the SCM to galvanic stimulation (3mA, 1ms). The cathodal electrode was on the mastoid, and the anodal electrode was on the forehead. Twenty-two healthy subjects and 28 patients with vestibular disorders were studied. All of the 28 patients showed the unilateral absence of vestibulo-collic reflexes evoked by 95dBnHL clicks on the affected side. RESULTS In healthy subjects mastoid-forehead galvanic stimulation produced a positive-negative biphasic EMG response at short latency on the SCM ipsilateral to the cathodal electrode. All patients with labyrinthine lesions showed biphasic EMG responses even in the affected side. In contrast, almost all patients with retro-labyrinthine lesions (16/18) showed no response or a decreased response on the affected side. CONCLUSIONS These results suggest that galvanic-evoked myogenic responses on the SCM may be useful in the differential diagnosis of labyrinthine lesions from retro-labyrinthine lesions in patients with an absence of vestibulo-collic reflexes evoked by clicks.
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Affiliation(s)
- Toshihisa Murofushi
- Department of Otolaryngology, Faculty of Medicine, University of Tokyo, 7-3-1 Hongo, Tokyo 113-8655, Japan.
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Kennedy PM, Inglis JT. Modulation of the soleus H-reflex in prone human subjects using galvanic vestibular stimulation. Clin Neurophysiol 2001; 112:2159-63. [PMID: 11682356 DOI: 10.1016/s1388-2457(01)00665-4] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
OBJECTIVES To determine if vestibular-evoked modulation of the soleus H-reflex can be achieved in a muscle that is not being used for postural support. METHODS Ten healthy subjects lay prone while the right leg was supported. In this position soleus H-reflex amplitudes were measured with the head facing forward, coupled with ipsilateral monopolar monaural galvanic stimulation (anode or cathode). To evaluate the interval between the onset of the galvanic stimulus and tibial nerve stimulation, the timing was varied between 0 and 200 ms in 20 ms intervals. A two-way ANOVA and student's t-test was performed to compare the mean amplitudes of the test and conditioned H-reflexes. RESULTS Galvanic stimulation significantly modified the amplitude of the H-reflex in a prone lying subject (P<0.05). Furthermore, the peak inhibitory and facilitatory effect occurred when the galvanic vestibular stimulus was delivered 100 ms prior to the H-reflex stimulus. CONCLUSIONS The results of this study demonstrate that galvanic stimulation can modulate the excitability of the soleus motoneuron pool when the muscle is not being used posturally. This suggests that in certain situations, it may be possible to use this type of vestibular stimulation to examine the integrity of descending vestibulospinal pathways in prone human subjects.
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Affiliation(s)
- P M Kennedy
- School of Human Kinetics, The University of British Columbia, 210-6081 University Boulevard, British Columbia, V6T 1Z1, Vancouver, Canada
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Watson SR, Fagan P, Colebatch JG. Galvanic stimulation evokes short-latency EMG responses in sternocleidomastoid which are abolished by selective vestibular nerve section. ELECTROENCEPHALOGRAPHY AND CLINICAL NEUROPHYSIOLOGY 1998; 109:471-4. [PMID: 10030677 DOI: 10.1016/s0924-980x(98)00033-2] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
OBJECTIVE To describe vestibulocollic responses in sternocleidomastoid (SCM) evoked by transmastoid galvanic (DC) stimulation. METHODS We studied the averaged responses in the unrectified EMG of SCM to transmastoid galvanic stimulation (5 mA/2 ms) and also to 100 dB clicks. Two patients with Meniere's disease were studied both before and after unilateral selective vestibular nerve section. RESULTS Transmastoid galvanic stimulation produced a positive-negative biphasic EMG response at short latency in the SCM ipsilateral to the side of cathode placement, which resembled that which followed vestibular activation by loud clicks (p13/n23). Selective unilateral vestibular nerve section abolished this galvanic-evoked response. CONCLUSIONS Galvanic-evoked vestibulocollic responses can be recorded in SCM. This is a new method of studying vestibular reflex function which may have application in the clinical assessment of vestibular disorders.
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Affiliation(s)
- S R Watson
- Institute of Neurological Sciences, The Prince of Wales Hospital, Randwick, Sydney, Australia
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Watson SR, Colebatch JG. Vestibulocollic reflexes evoked by short-duration galvanic stimulation in man. J Physiol 1998; 513 ( Pt 2):587-97. [PMID: 9807006 PMCID: PMC2231297 DOI: 10.1111/j.1469-7793.1998.587bb.x] [Citation(s) in RCA: 111] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
1. Vestibular-dependent responses in leg muscles following transmastoid galvanic stimulation have been well characterized. Here we describe the properties of vestibulocollic responses evoked by transmastoid galvanic stimulation. 2. In twelve healthy human subjects we examined the averaged responses in unrectified sternocleidomastoid (SCM) EMG evoked by transmastoid stimulation using current pulses of 4 mA intensity and 2 ms duration. In ten subjects we also examined the effects of unilateral vestibular stimulation with the indifferent electrode at the vertex. In further experiments we studied the effects of different levels of background muscle activation, head position, current intensity and current duration. We compared these responses with click-evoked vestibulocollic responses in SCM. 3. A clearly defined biphasic response, beginning with a surface positivity, was recorded in the SCM ipsilateral to the side of cathode placement in all subjects. We refer to this as the p13/n23 [g] (galvanic) response, given the close similarity, in terms of waveform and latencies, to the previously described click-evoked p13/n23 vestibulocollic response. The amplitude of this response was linearly related to background muscle activation, current intensity and current duration, but independent of head position. Unilateral galvanic stimulation revealed the p13/n23 [g] response to be solely generated by the cathode. 4. A biphasic response beginning with a surface negativity (n12/p20 [g]) contralateral to the cathode was seen in all subjects and was generated by both the cathode contralaterally and the anode ipsilaterally. 5. Both the p13/n23 [g] and n12/p20 [g] potentials were abolished by selective vestibular nerve section and unaffected by severe sensorineural deafness. 6. We conclude that galvanic stimulation evokes short-latency vestibulocollic reflexes. These vestibulocollic reflexes have properties that are distinct from those described for galvanic-evoked vestibular reflexes in leg muscles, and which may be related to their differing physiological roles.
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Affiliation(s)
- S R Watson
- Institute of Neurological Sciences, Prince of Wales Hospital, Randwick, Sydney 2031, Australia
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