Vestibular Evoked Myogenic Potential (VEMP) Triggered by Galvanic Vestibular Stimulation (GVS): A Promising Tool to Assess Spinal Cord Function in Schistosomal Myeloradiculopathy

BACKGROUND: Schistosomal myeloradiculopathy (SMR), the most severe and disabling ectopic form of Schistosoma mansoni infection, is caused by embolized ova eliciting local inflammation in the spinal cord and nerve roots. The treatment involves the use of praziquantel and long-term corticotherapy. The assessment of therapeutic response relies on neurological examination. Supplementary electrophysiological exams may improve prediction and monitoring of functional outcome. Vestibular evoked myogenic potential (VEMP) triggered by galvanic vestibular stimulation (GVS) is a simple, safe, low-cost and noninvasive electrophysiological technique that has been used to test the vestibulospinal tract in motor myelopathies. This paper reports the results of VEMP with GVS in patients with SMR. METHODS: A cross-sectional comparative study enrolled 22 patients with definite SMR and 22 healthy controls that were submitted to clinical, neurological examination and GVS. Galvanic stimulus was applied in the mastoid bones in a transcranial configuration for testing VEMP, which was recorded by electromyography (EMG) in the gastrocnemii muscles. The VEMP variables of interest were blindly measured by two independent examiners. They were the short-latency (SL) and the medium-latency (ML) components of the biphasic EMG wave. RESULTS: VEMP showed the components SL (p = 0.001) and ML (p<0.001) delayed in SMR compared to controls. The delay of SL (p = 0.010) and of ML (p = 0.020) was associated with gait dysfunction. CONCLUSION: VEMP triggered by GVS identified alterations in patients with SMR and provided additional functional information that justifies its use as a supplementary test in motor myelopathies.