Motor Nerve Conduction Study of Lumbosacral Spinal Stenosis with Magnetic Stimulation

Han, Tai Ryoon; Bang, Moon Suk; Kwon, Bum Sun

Abstract

The diagnostic value of nerve conduction study of spinal stenosis is far limited due to its deeply located lesion and its very short length of diseased nerve compared to the relatively long length of total conduction distance. Recently it became possible to stimulate the deep sited spinal nerve roots non-invasively with magnetic stimulation. The authors made a new method to calculate the motor nerve conduction time of lumbar spinal root using magnetic stimulation and planned to verify the delayed conduction time in patients with spinal stenosis who didn't show any abnormalities in the conventional electrophysiologic studies(peripheral nerve conduction velocity, F-wave and needle EMG). Three steps of magnetic stimulation were applied to vertex(transcortical stimulation), T12 spinous process(thoracic stimulation) and S1 spinous process(sacral stimulation), and three channel recording were performed at rectus abdominis(RA), right and left abductor hallucis(AH) simultaneously. Central motor conduction time(CMCT) was calculated by time difference between vertex and spinal stimulation at RA and AH. Lumbar-segment motor conduction time(LMCT) was defined as conduction time by subtracting CMCT of RA from CMCT of AH. The results as follows; LMCT was delayed in the group of patients with spinal stenosis(5.36+/-2.11 msec) compared to the normal control group(4.05+/-1.23 msec), but the range of LMCT was not quite different individually. Dividing the patients group into multi-level and single-level spinal stenosis group, LMCT in the multi-level spinal stenosis group was 6.12+/-1.95 msec which was significantly different from that of single-level(4.48+/-1.96 msec). The authors conclude that LMCT, the short segmental motor nerve conduction study of lumbosacral nerve root, is useful to confirm the entrapment of spinal nerve root across the lumbosacral spinal canal and is also non- invasive, simple and applicable to any other spinal nerve roots.