Intrarater and interrater agreement and reliability of vestibular evoked myogenic potential triggered by galvanic vestibular stimulation (galvanic-VEMP) for HTLV-1 associated myelopathy testing

Abstract

BackgroundThe vestibular evoked myogenic potential triggered by galvanic vestibular stimulation (galvanic-VEMP) has been used to assess the function of the vestibulospinal motor tract and is a candidate biomarker to predict and monitor the human T-cell lymphotropic virus type 1 (HTLV-1) associated myelopathy (HAM). This study determined the agreement and reliability of this exam.MethodsGalvanic-VEMP was performed in 96 participants, of which 24 patients presented HAM, 27 HTLV-1-asymptomatic carriers, and 45 HTLV-1-negative asymptomatic controls. Galvanic vestibular stimulation was achieved by passing a binaural and bipolar current at a 2 milliamperes (mA) intensity for 400 milliseconds (ms) between the mastoid processes. Galvanic-VEMP electromyographic wave responses of short latency (SL) and medium latency (ML) were recorded from the gastrocnemius muscle. Intrarater (test-retest) and interrater (two independent examiners) agreement and reliability were assessed by standard error of measurement (SEM), coefficient of repeatability (CR), intraclass correlation coefficient (ICC), and Kappa coefficient.ResultsIn the total sample (n = 96), SL and ML medians were 56 ms (IQR 52–66) and 120 ms (IQR 107–130), respectively. The intrarater repeatability measures for SL and ML were, respectively: SEM of 6 and 8 ms; CR of 16 and 22 ms; ICC of 0.80 (p<0.001) and 0.91 (p<0.001); and a Kappa coefficient of 0.53 (p<0.001) and 0.82 (p<0.001). The interrater reproducibility measures for SL and ML were, respectively: SEM of 3 and 10 ms; CR of 8 and 27 ms; ICC of 0.95 (p<0.001) and 0.86 (p<0.001); and a Kappa coefficient of 0.77 (p<0.001) and 0.88 (p<0.001).ConclusionGalvanic-VEMP is a reliable and reproducible method to define the integrity of the vestibulospinal tract. Longitudinal studies will clarify its validity in the clinical context, aimed at achieving an early diagnosis and the monitoring of HAM.

Vestibular Evoked Myogenic Potential on Ocular, Cervical, and Soleus Muscles to Assess the Extent of Neurological Impairment in HTLV-1 Infection

“…In accordance with the present study, previous studies have already shown that ML is the best component to discriminate changes since this peak is easier to define with the best intrarater and interrater agreement and presents the best area under the ROC curve comparing to SL (47)(48)(49). Conversely, SL can be often indistinguishable from the baseline and its measurement has presented the worst interrater correlation comparing to ML (45,(47)(48)(49).…”

“…The changes in oVEMP have occurred only in HAM group, which indicates a midbrain involvement. This finding is precisely in accordance with the best knowledge about HAM physiopathology and reinforces the validity and accuracy of VEMP for clinical use (44)(45)(46)(47)(48)(49). In this study, the best contribution of VEMP in the evaluation of the HTLV-1 population was to the asymptomatic infection.…”

“…The sVEMP was a reliable and reproducible method to define the integrity of the vestibulospinal tract, with an excellent intrarater and interrater agreement and reliability. Both in HAM and SMR, the component ML was shown to be the most reliable to define alteration (47,48).…”

Center of gravity oscillations in HTLV-1-associated myelopathy/tropical spastic paraparesis

“…They are the main responsible for voluntary motricity [19]. Recent studies [6,21,22] have pointed to the involvement of the spinal cord and the brain in the loss of postural control. The loss of postural control may have its origin in the suprasegmental system.…”

Ocular vestibular evoked myogenic potential (VEMP) reveals mesencephalic HTLV-1-associated neurological disease

“…The subclinical spinal cord injury related to HAM has been already shown through VEMP of cervical and of lower limbs muscles, exams that are used to test the vestibulo-collic reflex [8,9,13,16,17]. The present study proposes the use of VEMP of the oculomotor system (ocular VEMP) to test the brainstem pathways associated with body balance to verify the extension of the HTLV-1-neurological damage.…”