Detecting neuropathy using measures of motor unit activation extracted from standard concentric needle electromyographic signals

Objective: Motor unit loss associated with neuropathic disorders affects motor unit activation. Quantitative electromyographic (EMG) features of motor unit activation estimated from the sequences of motor unit potentials (MUPs) created by concurrently active motor units can support the detection of neuropathic disorders. Interpretation of most motor unit activation feature values are, however, confounded by uncertainty regarding the level of muscle activation during EMG signal detection. A set of new features circumventing these limitations are proposed, and their utility in detecting neuropathy is investigated using simulated and clinical EMG signals. Methods: The firing sequence of a motor neuron was simulated using a compartmentalized Hodgkin-Huxley based model. A pool of motor neurons was modelled such that each motor neuron was subjected to a common level of activation. The detection of the firing sequence of a motor neuron using a clinically detected EMG signal was simulated using a model of muscle anatomy combined with a model representing muscle fiber electrophysiology and the voltage detection properties of a concentric needle electrode. Significance: Findings are based on simulated EMG data representing 30 normal and 30 neuropathic muscles as well as clinical EMG data collected from the tibialis anterior muscle of 48 control subjects and 30 subjects with neuropathic disorders. These results demonstrate the possibility of detecting neuropathy using motor unit recruitment and mean firing rate feature values estimated from standard concentric needle detected EMG signals.