T127. Electrophysiological study on selecting damage of fast motor neuron in early stage of ALS

Introduction The motor neuronal damage is selective in the early stage of amytrophic lateral sclerosis (ALS), and the large motor neurons with rapid conduction may be the earliest involved. The purpose of this study is based on the analysis of the correlation between the changes of F wave minimum latencies, distal motor latencies (DML) and the compound muscle action potentials (CMAP) and negative area of CMAP to seek for the evidence supporting preferential vulnerability of fast motor neuron in early stage of ALS. Methods This study enrolled the definite and probable diagnosis ALS (according to revised EI criteria) patients in our outpatient clinic from January 2016 to October 2017. The inclusion criteria of early ALS patients: the strength of upper limbs higher than 3/5 MRC levels and revised ALS-FRS score greater than 25 points. In addition, the matched healthy people were selected as the control group. All participants were evaluated by physical examination, nerve conduction studies, and standard needle EMG and we focused on the values including DML, CMAP (from the baseline to negative wave peaks), negative peak area and F wave of minimum latencies in the median nerve. Results Forty-five patients (27 male) of ALS group, mean 55.8 ± 11.9 years, height 165.8 ± 6.7 cm,duration of disease 12.3 ± 6.3 months, revised ALS-FRS score 31.5 ± 4.1. The site of symptom onset from upper limb was 27 (60%), and from bulbar was 18 (40%). In the normal control group, there were 46 (27 male) subjects, mean 56.3 ± 12.0 years, height 164.6 ± 7.4 cm. Age, gender and height matched with ALS group. DML in the median showed no significant difference ( P  = 0.138) between control and ALS group, meanwhile the median nerve conduction velocity showed in normal range. But the minimal latencies of F wave revealed more longer ( P P P R  = −0.593, P  ± 0.001; R  = −0.530, P  = 0.001), and did the same pattern to the F wave minimum latency ( R  = −0.635, P  = 0.001; R  = 0.634, P  = 0.001). Conclusion Based on the evidence of negative correlation between mildly prolonged the minimal latency of the F wave and decreased CMAP or negative wave area, the fast motor neurons show preferentially vulnerable in the early stage of ALS.