Coherence and Phase Locking Disruption in Electromyograms of Patients with Amyotrophic Lateral Sclerosis

摘要

In motor neuron disease, the aim of therapy is to prevent or slow neuronal degeneration and early diagnosis is thus essential. Hypothesising that beta-band (15-30 Hz) is a measure of pathways integrity as shown in literature, coherence and phase locking factor (PLF) could be used as an electrophysiological indicator of upper and lower neuron integrity in patients with amyotrophic lateral sclerosis (ALS). In this work are applied such tools in different variable situations. Coherence and PLF analysis was computed for EMG signals registered from 2 groups: control subjects and ALS patients. The data was recorded during instants of steady contraction for both contra and ipsilateral acquisitions. Ipsilateral coherence and PLF was computed for one member of each group and results present significant differences between both groups. Contrarily, contralateral acquisitions were performed on 6 members of each group and both coherence and PLF results present no significant differences. So, while control subjects present no neuronal or muscular disorders and therefore higher synchrony and coherence for beta-band EMG signals, patients with ALS do not present synchronism or coherence in any frequency, specially for beta-band. All results allowed to conclude that contralateral coherence is not a good measure of corticospinal pathways integrity. However, ipsilateral acquisitions show promising results and it is possible to affirm that ipsilateral measurements may reflect neuronal degeneration. For future work is suggested a deeper analysis of PLF, that appear to have potential as a quantitative test of upper and lower neuron integrity related to ALS.