Increased neuromuscular transmission instability and motor unit remodelling with diabetic neuropathy as assessed using novel near fibre motor unit potential parameters

Objective: To assess the degree of neuromuscular transmission variability and motor unit (MU) remodelling in patients with diabetic polyneuropathy (DPN) using decomposition-based quantitative electromyography (DQEMG) and near fibre (NF) motor unit potential (MUP) parameters. Methods: The tibialis anterior (TA) muscle was tested in 12 patients with DPN (65 +/- 15 years) and 12 controls (63 +/- 15 years). DQEMG was used to analyze electromyographic (EMG) signals collected during voluntary contractions. MUP and NF MUP parameters were analyzed. NF MUPs were obtained by high-pass filtering MUP template waveforms, which isolates contributions of fibres that are close to the needle detection surface. NF MUP parameters provided assessment of motor unit size (NF area), fibre density (NF fibre count) and contribution dispersion (NF dispersion) and neuromuscular transmission instability (NF jiggle). Results: DPN patients had larger (+45% NF area), more complex (+30% NF fibre count), and less stable (+30% NF jiggle) NF MUPs (p < 0.05). No significant relationships were found between NF MUP stability and denervation, or strength; however NF MUP complexity was positively related to TA denervation in the DPN group (r = 0.63; p < 0.05). NF MUP complexity and instability were positively related in DPN patients (r = 0.46; p < 0.05). Conclusions: DPN is associated with neuromuscular transmission instability and MU remodelling that can be assessed using DQEMG. Significance: DQEMG-derived NF MUP parameters may be useful in identifying patients in early stages of neuromuscular dysfunction related to DPN. (C) 2014 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.