Abstract
PurposeVestibular Myogenic Evoked Potential (VEMP) evaluates vestibulo-ocular and vestibulo-collic reflexes involved in the function of the otolithic organs and their afferent pathways. We compared the results of cervical and ocular VEMP in HTLV-1 associated myelopathy (HAM) and HTLV-1-asymptomatic infection.Participants and methodsThis cross-sectional study included 52 HTLV-1-infected individuals (26 HAM and 26 asymptomatic carriers) and 26 seronegative controls. The groups were similar regarding age and gender. Participants underwent simultaneous ocular and cervical VEMP. The stimulus to generate VEMP was a low-frequency tone burst sound tone burst, with an intensity of 120 decibels normalized hearing level, bandpass filter from 10 to 1,500 Hertz (Hz), with 100 stimuli at 500 Hz and 50 milliseconds recording time. The latencies of the electrophysiological waves P13 and N23 for cervical VEMP and N10 and P15 waves for ocular VEMP were compared among the groups. The absence or delay of the electrophysiological waves were considered abnormal results.ResultsOcular VEMP was similar among the groups for N10 (p = 0.375) and different for P15 (p≤0.001). Cervical VEMP was different for P13 (p = 0.001) and N23 (p = 0.003). About ocular VEMP, in the HTLV-1-asymptomatic group, normal waves were found in 23(88.5%) individuals; in HAM group, normal waves were found in 7(26.9%). About cervical VEMP, 18(69.2%) asymptomatic carriers presented normal waves and only 3(11.5%) patients with HAM presented normal waves. Abnormalities in both VEMPs were found in 1(3.8%) asymptomatic carrier and in 16(61.5%) patients with HAM.ConclusionNeurological impairment in HAM was not restricted to the spinal cord. The mesencephalic connections, tested by ocular VEMP, have been also altered. Damage of the oculomotor system, responsible for eye stabilization during head and body movements, may explain why dizziness is such a frequent complaint in HAM.
Highlights
The Human T-cell lymphotropic virus type 1 (HTLV-1) infection affects approximately 5–10 million people worldwide [1]
About ocular vestibular evoked myogenic potential (VEMP), in the HTLV-1-asymptomatic group, normal waves were found in 23(88.5%) individuals; in HTLV-1-associated myelopathy (HAM) group, normal waves were found in 7(26.9%)
About cervical VEMP, 18 (69.2%) asymptomatic carriers presented normal waves and only 3(11.5%) patients with HAM presented normal waves. Abnormalities in both VEMPs were found in 1(3.8%) asymptomatic carrier and in 16(61.5%) patients with HAM
Summary
The Human T-cell lymphotropic virus type 1 (HTLV-1) infection affects approximately 5–10 million people worldwide [1]. The host genetic and immunological factors seem to be related to the development of HTLV-1-associated diseases [1,2]. The range of neurological manifestations of HTLV-1-associated myelopathy (HAM) includes the spine, with the classical motor limitations affecting the lower limbs, and the autonomic dysfunction [3]. The complaint of dizziness has proven to be frequent in patients with HAM and can be one of the first symptoms of HTLV-1-neurological impairment [8,9]. Individuals infected with HTLV-1 may present vague complaints, with no motor, sensitive, or autonomic abnormalities [4,5,6]. HAM diagnosis is based on clinical criteria that reveals established neurological damage [10]
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