Lower Motor Neuron Hyperexcitability in Amyotrophic Lateral sclerosis: Anaylsis Using Motor Evoked Potentials

Bae, Jong-Seok; Hong, Suk-Chan; Kim, Min-ky; Kim, Byoung-Joon

Ann Clin Neurophysiol > 2003 ;5(1) > Article

Ann Clin Neurophysiol. 2003; 5(1): 21-26.

Jong-Seok Bae, Suk-Chan Hong, Min-ky Kim, and Byoung-Joon Kim

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

ABSTRACT

Backgroun & Objectives : Hyperexciability of motor system is a well-established characteristic pathophysiologic finding of mayotrophic lateral sclerosis (ALS). Whereas little is known about the source of excitability according to the progression of the disease. We evaluated the excitability and its source in advanced ALS patients using transcranial magnetic stimulation(TMS). Material & Methods : Motor evoked potentials (MEP) by TMS were recorded for abductor pollicis brevis muscles in 20 patients, 11men and 9 women, with ALS. Mean age was 54.2?2.1 years, and mean disease duration was 13.9?3.4 years. Serial magnetic stimulations were applied to get the parameters; excitability threshold (ET), amplitude and latency of MEP. We also had a facilitated MEP (fMEP). Results : The parameters were analyzed according to the clinical setting. ET was higher in ALS(mean 63.5?8.1) than normal control (mean 46.0?.4 , p<0.01). Amplitudes of MEP were reduced I ALS (2.6?.6 mV ; control 6.5?.1mV, p<0.01). Duration of the disease and ET showed significant inverse correlation (Spearson correlation coefficient = -0.57, p<0.01). Duration of the disease and fMEP/MEP ratio showed less but also significant inverse correlation(Spearson correlation coefficient, r=-0,52, p<0.05). Conclusions : Lower ET in advanced ALS patients, in spite of decreased fMEP/MEP ratio, may indicate the hyperexcitability of lower motor neuron in these patients. This study suggests that lower motor neurons is hyperexciable due to upper motor neuron dysfunction at advanced stage.

Key words: Amyotrophic lateral sclerosis, Motor evoked potential, Hyperexcitability