Contribution of Galvanic Vestibular Stimulation for the Diagnosis of HTLV-1-Associated Myelopathy/Tropical Spastic Paraparesis

Abstract

Background and PurposeGalvanic 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.MethodsBipolar 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).ResultsThe 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.ConclusionsA 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.

Aplicações dos potenciais evocados miogênicos vestibulares: revisão sistemática de literatura

“…The studies about VEMP with auditory stimulation have evidenced this test as an assisting tool for the diagnosis of several types of peripheral vestibular disorders, predominantly Meniere's disease (5,6,29,40) and superior semicircular canal dehiscence (SSCD) (8)(9)(10)(11)32) , as well as diseases related to central vestibular disorders, such as motor myelopathies (19)(20)(21)(22)(23)(24)(25) and Parkinson's disease (15,(41)(42)(43) .…”

“…As galvanic stimulation reaches the terminal axons of the vestibular nerve in the junction with the vestibular nucleus, when comparing the response to VEMP using auditory stimulation with that of VEMP using galvanic stimulation in the same patient, it is possible to differentiate whether the lesion is vestibular or retrovestibular (42,(45)(46)(47) . For example, in the presence of peripheral vestibular neuropathy, VEMP with auditory stimulation will show altered results, whereas VEMP with galvanic stimulation will present normal result (25) .…”

“…VEMP with galvanic stimulation has been proved to be an important tool for the subclinical diagnosis of motor myelopathies (20,21,25) and for the definition of the level of spinal cord involvement (19)(20)(21) . For instance, when assessing patients with motor or traumatic myelopathy and submitting them to VEMP with galvanic stimulation with the response recorded in different postural muscles (e.g.…”

“…The VEMP has been utilized to study a variety of vestibular diseases. Among peripheral diseases, Meniere's disease (5,6) , vestibular neuritis (7) , superior semicircular canal dehiscence (8)(9)(10) , large vestibular aqueduct syndrome (11) , and vestibular schwannoma (12,13) are highlighted, whereas among central vestibular diseases, vestibular migraine (14) , Parkinson's disease (15) , central ischemic lesions (16)(17)(18) , and motor myelopathies (19)(20)(21)(22)(23)(24)(25) stand out.…”

Electrophysiological Analysis Shows Dizziness as the First Symptom in Human T Cell Lymphotropic Virus Type-Associated Myelopathy/Tropical Spastic Paraparesis

“… 4 , 5 Thus, it is expected that the reflexes related to body balance may be altered in HAM/TSP. 4 Actually, frequent complaints of dizziness among individuals with HAM/TSP has been reported 6 , 7 and damage of the vestibulospinal pathway was identified through vestibular-evoked myogenic potential (VEMP) as a precocious electrophysiological alteration of individuals who afterward developed HAM/TSP. 6 , 8 , 9 However, dizziness as a clinical manifestation has not yet been correlated with the electrophysiological alterations of the vestibulospinal pathway and had not yet been analyzed as a prognostic marker of HAM/TSP.…”