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LETTER TO EDITOR
Year : 2010  |  Volume : 58  |  Issue : 5  |  Page : 796-797

Magnetic augmented translumbosacral stimulation coil stimulation method for accurate evaluation of corticospinal tract function in peripheral neuropathy


1 Department of Neurology, Division of Neuroscience, Graduate School of Medicine, The University of Tokyo, Japan
2 Department of Neurology, School of Medicine, Fukushima Medical University, Japan

Date of Acceptance27-Jul-2010
Date of Web Publication28-Oct-2010

Correspondence Address:
Hideyuki Matsumoto
Department of Neurology, Division of Neuroscience, Graduate School of Medicine, The University of Tokyo
Japan
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0028-3886.72183

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How to cite this article:
Matsumoto H, Shirota Y, Ugawa Y. Magnetic augmented translumbosacral stimulation coil stimulation method for accurate evaluation of corticospinal tract function in peripheral neuropathy. Neurol India 2010;58:796-7

How to cite this URL:
Matsumoto H, Shirota Y, Ugawa Y. Magnetic augmented translumbosacral stimulation coil stimulation method for accurate evaluation of corticospinal tract function in peripheral neuropathy. Neurol India [serial online] 2010 [cited 2019 Oct 13];58:796-7. Available from: http://www.neurologyindia.com/text.asp?2010/58/5/796/72183


Sir,

The limitation of magnetic stimulation is that the prolongation of the central motor conduction time (CMCT) does not exactly indicate the involvement of the corticospinal tract when the spinal nerves are involved, because magnetic stimulation over the spinal enlargements activates the spinal nerves at the neuro-foramina level. [1] Especially for leg muscles, the conduction delay of long spinal nerves (i.e., cauda equina) readily contributes to CMCT prolongation. Recently, we have developed a novel method to activate the most proximal cauda equina around the conus medullaris using a magnetic augmented translumbosacral stimulation (MATS) coil [Figure 1]. [2] We have also reported that the conduction time from the motor cortex to the conus medullaris (cortico-conus motor conduction time, CCCT) can be assessed using the MATS coil in healthy subjects. [3] Here, we demonstrate that the CCCT is hardly affected even when the nerve conduction of peripheral nerves is severely delayed.
Figure 1 :L1 level - MATS coil stimulation method The MATS coil should be placed on the side opposite the recorded muscle. The edge of the MATS coil should be positioned over the first lumbar spinous process for inducing currents to flow upward

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The patient was a 28-year-old man who presented with muscle weakness, sensory disturbance and areflexia. He had no complaint or symptom related to corticospinal tract. He has been diagnosed as a case of Charcot-Marie-Tooth (CMT) disease type 1 after gene analysis, a mutation of myelin protein zero. Nerve conduction studies showed severe slowing of conduction (<10 m/s) in the upper and lower extremities. A MATS coil stimulation study was performed to measure CCCT [Figure 2]. Motor-evoked potentials were recorded from the right biceps femoris muscle. This proximal muscle was selected because it was intact, compared to the distal muscles with severe muscular atrophy. Transcranial magnetic stimulation was performed during voluntary contraction of the target muscle. The cortical latency was severely prolonged [133.2 ms; normal value is 21.8±1.0 ms (mean±SD, the data of age- and body height-matched 10 normal subjects)]. Subsequent L1 level MATS coil stimulation performed during relaxation showed that the L1 level latency was also severely prolonged (119.8 ms; normal value, 8.9±0.8 ms). In contrast, the CCCT was within normal limits (13.4 ms; normal value, 12.9±1.1 ms).

In CMT disease, peripheral motor conduction is uniformly involved both proximally and distall, [4] although the central motor conduction is intact. Indeed, the CCCT was normal. Therefore, we consider that the CCCT obtained using the MATS coil stimulation method is a useful parameter to evaluate the accurate corticospinal tract function, even in patients with severe peripheral neuropathy. In earlier reports of hereditary neuropathies, a possibility of involvement of central pathways has been raised, [5] which could have been caused by a faulty technique of CMCT measurement. Furthermore, methods to measure CMCT using F-waves or tendon reflex latency (T-response) also are unreliable in cases of proximal nerve conduction delay. For reliability of the direct activation of the most proximal cauda equina, we propose that the central motor conduction be evaluated using the MATS coil stimulation method in patients with peripheral neuropathy.
Figure 2 :MATS coil stimulation study of a patient with Charcot-Marie- tooth disease type 1 (a); and a normal subject (b) The upper trace shows motor-evoked potentials elicited by transcranial magnetic stimulation (cortical latency); and lower trace, L1 level MATS coil stimulation (L1 level latency). The CCCT is obtained by subtracting the L1 level latency from the cortical latency

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  Acknowledgments Top


We are grateful to Drs. Ritsuko Hanajima, Masashi Hamada and Yasuo Terao (Department of Neurology, The University of Tokyo, Japan) for advice in this investigation.

 
  References Top

1.Ugawa Y, Rothwell JC, Day BL, Thompson PD, Marsden CD. Magnetic stimulation over the spinal enlargements. J Neurol Neurosurg Psychiatry 1989;52:1025-32.  Back to cited text no. 1
[PUBMED]  [FULLTEXT]  
2.Matsumoto H, Octaviana F, Terao Y, Hanajima R, Yugeta A, Hamada M, et al. Magnetic stimulation of the cauda equina in the spinal canal with a flat, large round coil. J Neurol Sci 2009;284:46-51.  Back to cited text no. 2
[PUBMED]  [FULLTEXT]  
3.Matsumoto H, Hanajima R, Shirota Y, Hamada M, Terao Y, Ohminami S, et al. Cortico-conus motor conduction time (CCCT) for leg muscles. Clin Neurophysiol 2010;121:1930-1933.  Back to cited text no. 3
[PUBMED]  [FULLTEXT]  
4.Kaku DA, Parry GJ, Malamut R, Lupski JR, Garcia CA. Uniform slowing of conduction velocities in Charcot-Marie-Tooth polyneuropathy type 1. Neurology 1993;43:2664-7.  Back to cited text no. 4
[PUBMED]    
5.Sartucci F, Sagliocco L, Murri L. Central motor pathway evaluation using magnetic coil stimulation in hereditary motor and sensory neuropathy type I (HMSN type I, Charcot-Marie-Tooth disease). Int J Neurosci 1997;92:145-59.  Back to cited text no. 5
[PUBMED]    


    Figures

  [Figure 1], [Figure 2]

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