Resposta eletromiográfica á estimulação vestibular galvânica na avaliação da lesão medular de pacientes com a mielorradiculopatia da esquitossomose mansônica

Abstract

Introduction: Myeloradiculopathy is the most severe ectopic form of mansonic schistosomiasis. Diagnosis is based on clinical evidence of myeloradiculopathy, evidence of exposure to Schistosoma mansoni, demonstration of inflammatory spinal cord injury in cerebrospinal fluid analysis and on magnetic resonance imaging (MRI) and exclusion of other spinal cord diseases. Treatment involves the use of schistosomicidal drugs and corticosteroids. Evaluation of therapeutic response is based on neurological examination and MRI. However, MRI may normalize even in the persistence of clinical abnormalities. In this context, neurophysiology tests, like evoked potentials, may be useful since they are more sensitive than MRI and more objective than neurological examination. Vestibular evoked myogenic potential with galvanic stimulation (VEMP-G) is a safe, inexpensive and easy to perform exam that tests the reticulospinal and vestibulospinal tracts, which are damaged in motor myelopathies. It had never been studied before in patients with schistosomal myeloradiculopathy (SMR). Objective: This study aimed at assessing the value of VEMP-G in diagnosing spinal cord injury in patients with SMR. Methodology: A cross-sectional comparative study was conducted with 22 SMR patients and 22 healthy control subjects. All participants (n=44) were submitted to clinical examination, neurological examination, VEMP-G and eleven patients also underwent MRI. The VEMP-G parameters studied were time of onset of short-latency (SL) and medium-latency (ML) electromyographic responses to vestibular galvanic stimulation, recorded in gastrocnemius muscle. Patients age ranged from 20 to 70 years (median: 42; p25: 28; p75: 52); 17 were male and five were female; time of SMR diagnosis ranged from one month to 16 years. Control individuals age ranged from 19 to 70 years (median: 30; p25: 26; p75: 44), being 12 male and 10 female. The groups were statistically similar regarding to age and sex (p=0.162 and p=0.203). Results: SL and ML, blindly measured, were augmented in patients compared to controls: 58.73ms (p25: 55.57; p75: 60.94) versus 63.77ms (p25: 59.68; p75: 74.18) for SL (p=0.001); 108.57ms (p25: 105.72; p75: 121.44) versus 137.57ms (p25: 122.43; p75: 152.71) for ML (p<0.001). Among patients, gait disturbance was the only neurologic abnormality associated to SL and ML delay (p=0.01 and p=0.024). Based on clinical examination as the gold standard, Receiving Operator Characteristics (ROC) curve showed area under the curve of 0.814 (p=0.001) for SL and 0.861 (p<0.001) for ML in the detection of spinal cord injury. Best cutoff points were 61.25ms (SL) and 120.54ms (ML). Sensitivity and specificity were, respectively, 79% and 77% (SL), 90% and 73% (ML). VEMP-G was more sensitive (S: 91%) than MRI (S: 9%) (p=0.004) in 11 patients that underwent both exams, all of them presenting abnormalities in clinical examination. Conclusion: VEMP-G was shown to detect spinal cord injury, including those not seen by MRI and may be of value for diagnosis and follow-up of SMR.