Abstract
During the voluntary contraction of target muscles, a silent period is observed immediately after the motor evoked potential (MEP) is elicited by transcranial magnetic stimulation. In this study, the silent period was recorded from bilateral abductor digiti minimi (ADM) and abductor hallucis (AH) in 30 normal healthy subjects (120 extremities) and 30 patients with cervical myelopathy (120 extremities). In normal subjects, the silent period was 142.3±41.0 ms (mean±SD) for ADM, and 83.6±42.3 ms for AH. When stimulus intensity was increased from 60% to 95%, the length of the silent period increased, reaching almost maximal level. The length of the silent period correlated with stimulus intensity, but not with the contraction force of voluntary muscles. In patients with cervical myelopathy, the silent period was 69.2±27.8 ms (mean±SD) for ADM and 48.3±17.0 ms for AH, significantly shorter than in the normal subjects. We believe that the length of the silent period can be a useful parameter for indicating the function of the spinal inhibitory system.
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Suyama, N., Shindo, H. & Iizuka, T. Study of the silent period following motor evoked potential by magnetic stimulation method. J Orthop Sci 1, 301–306 (1996). https://doi.org/10.1007/BF02348839
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DOI: https://doi.org/10.1007/BF02348839