title: Contribution of Galvanic Vestibular Stimulation for the Diagnosis of HTLV-1-Associated Myelopathy/Tropical Spastic Paraparesis.
abstract: OBJECTIVE
  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.
authors.affiliation: Faculty of Medicine, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil.
authors.forename: Luciana Cristina
authors.initials: LC
authors.lastname: Matos Cunha
authors.forename: Maurício
authors.initials: M
authors.lastname: Campelo Tavares
authors.forename: Carlos Julio
authors.initials: CJ
authors.lastname: Tierra Criollo
authors.forename: Ludimila
authors.initials: L
authors.lastname: Labanca
authors.forename: Clarissa
authors.initials: C
authors.lastname: Cardoso Dos Santos Couto Paz
authors.forename: Henrique
authors.initials: H
authors.lastname: Resende Martins
authors.forename: Anna Bárbara
authors.initials: AB
authors.lastname: de Freitas Carneiro-Proietti
authors.forename: Denise
authors.initials: D
authors.lastname: Utsch Goncalves
keywords: HAM/TSP; electrophysiology; galvanic vestibular stimulation; spinal cord diseases; vestibular-evoked myogenic potentials