The electrophysiological changes of lower limbs in subjects with spinal cord injury

Objective:To investigate the electrophysiological changes of peripheral nerves and muscles of lower limbs in patients with spinal cord injury(SCI).Method:Standard sensory and motor nerve conductions examination were performed in tibial nerve,peroneal nerve to analyze distal motor latency,compound muscle action potential(CMAP),sensory nerve conduction velocity(SNCV) and Sensory nerve action potential(SNAP).Concentric needle electromyography was used in examination of bilateral tibial anterior,vastus medialis,lateral gastrocnemius and paraspinal musles at L4—S1 level to record spontaneous activities(SA).Result:①Characteristics of nerve conduction:94.7% patients had abnormal motor nerve conduction with decreased CMAP amplitude,prolonged distal motor latency(DML) and absent response.Abnormal sensory conductions were found in 15.8% patients,including slowed SNCV,low SNAP amplitude and no response.②Tibial nerve:Simple abnormal motor conductions were found in 47.4% patients and abnormal motor and sensory conductions coexisted in 10.5% patients.Abnormal motor conductions were seen in both sides(no response,decreased CMAP amplitude and/or prolonged DML).The characteristics of sensory conduction were unilaterally slowed SNCV and decreased SNAP amplitude.③Peroneal nerve:Simple abnormal motor conductions were found in 78.9% patients and abnormal motor and sensory conduction coexist in 15.8% patients.84.2% patients had bilaterally abnormal motor conductions with no response and/or decreased CMAP amplitude.Unilaterally abnormal conductions were seen in 10.5% patients with decreased CMAP amplitude and delayed DML.The characteristics of sensory conduction showed slowed SNCV,decreased SNAP amplitude and no response in one or both sides(15.8%).④Compared to cervical level SCI,the ratio of abnormal conduction of tibial(66.7%:42.9%) and peroneal nerve(100%:85.7%) in thoracolumbar level SCI increased significantly.⑤SA,including fibrillations and positive sharp waves,were noted at variable degrees in all muscles examined.Conclusion:Axonal motor neuropathy and abnormal SA in lower extremities were the main electrophysiological characteristics in patients with SCI.And there was no correlation between SA and the electrophysiological changes of peripheral nerves.The ratio of abnormal nerve conduction of lower extremities with thoracolumbar level SCI was higher than that with cervical level.