Potencial evocado miogênico vestibular como marcador de progressão da mielopatia associada ao HTLV-1: seguimento de 10 anos

Abstract

Introduction: Human T-lymphotropic virus type 1-associated myelopathy (HAM) is a chronic inflammation of the spinal cord that results in posture and gait impairment. The diagnosis of HAM is typically delayed, and galvanic vestibular-evoked myogenic potential (G-VEMP) may serve as a promising tool to aid in the early diagnosis of HAM. Objectives: To assess the role of G-VEMP as a progression marker for HAM based on the vestibulospinal reflex response. Methods: This is a longitudinal study involving asymptomatic individuals infected with HTLV1 and those with possible HAM (p-HAM) followed from 2012/13 to 2022/23. All participants underwent neurological evaluation, application of the Motor Disability Scale (OMDS), and GVEMP at the beginning of the study (T0), after 4 years (T1), and after 10 years from the first assessment (T2). The defined outcome was the confirmed diagnosis of HAM. Galvanic stimulation was applied to the mastoid processes, and G-VEMP was recorded bilaterally in the gastrocnemius muscle. Considered parameters of G-VEMP were latency and amplitude of short-latency (SL) and medium-latency (ML) responses. Study variables were compared using the Friedman test and Cochran's Q test. A significance level of 0.05 was considered for statistical significance. Results: The study included 31 participants. At T0, the average age was 58 years, with 21 (68%) being women. At the beginning of follow-up, individuals were allocated into two groups: asymptomatic (26/31) and p-HAM (5/31). Over 10 years of followup, the comparative analysis of OMDS showed a difference between T0xT2 (p=0.001) and T1xT2 (p=0.003) indicating clinical deterioration. Regarding G-VEMP parameters, both SL and ML latency increased (p<0.001), and amplitude decreased (p<0.001). Among asymptomatic individuals at T0 (n=26), 5/26 (19%) showed altered G-VEMP. Of these, 4/5 progressed to p-HAM, and 1/5 progressed to HAM (1/26; 4%) at T2. In the p-HAM group at T0 (n=5), all (100%) had altered G-VEMP. Of these, 2/5 progressed to HAM at T1, and 1/5 at T2, totaling 3/5 HAM (60%). Over the 10-year follow-up, G-VEMP accuracy in predicting progression to HAM was 93%, with a sensitivity of 83% and specificity of 100%. Conclusion: G-VEMP served as a marker for myelopathy progression as the potential changed before HAM became clinically evident. Therefore, it can assist in predicting which asymptomatic individuals are at a higher risk of evolving into HAM