Motor unit number estimation by decomposition‐enhanced spike‐triggered averaging: Control data, test–retest reliability, and contractile level effects

Abstract

Decomposition-enhanced spike-triggered averaging (DE-STA) has been developed as a method for obtaining a motor unit number estimate (MUNE). We describe the method and report control data for the first dorsal interosseous/adductor pollicis and thenar muscles and reliability in the thenar muscles. Seventeen subjects (ages 20-50 years) took part in the study. The maximum M potential was elicited with supramaximal stimulation of the ulnar or median nerve at the wrist. Surface and intramuscularly detected electromyographic signals were then collected simultaneously during mild to moderate contractions. Decomposition algorithms were used to detect and sort the individual motor unit potential (MUP) occurrences of several concurrently active motor units in the needle-detected signals. The MUP occurrences were used as triggering sources to estimate their corresponding surface-detected MUPs (S-MUPs) using STA. The mean S-MUP size was calculated and divided into the maximum M-potential size to derive a MUNE. The MUNE values were consistent with those previously reported with other methods, and thenar MUNEs for the two trials were similar (249 +/- 78 and 246 +/- 90), with high test-retest reliability (r = 0.94, P < 0.05). DE-STA thus appears to be a valid and reliable method to obtain MUNEs.

Assessment of Motor Units in Neuromuscular Disease

“…These methods enabled more proximal muscles to be studied [44,45]. Modifications such as decomposition spike-triggered averaging used a computerized algorithm to analyze multiple individual motor unit potentials.…”

Motor unit number estimation may be a useful method to evaluate motor function recovery after spinal cord transection in rats

“…10,11 The compound muscle action potential of the MG muscle was obtained using a supramaximal stimulation (20-25% above the maximal intensity). 12,13 The cathode of the stimulating electrodes was inserted subcutaneously close to the sciatic nerve at the proximal thigh, and the anode was placed subcutaneously 1 cm proximally. Individual motor unit responses were obtained by adjusting the stimulating electrode and isolating threshold responses with distinct morphologies.…”

A neurophysiological approach to nerve transfer to restore upper limb function in cervical spinal cord injury

“…Isolating the target muscle can be achieved by recording with the needle electrode shaft (macro-EMG, 50 Conmac, 28 or concentric cannula) rather than the surface electrode. At our center, we have used a macro-EMG needle (macro-MUNE), described and validated by de Koning et al in 1988 18 using the spike-triggered average 3,5 (STA) MUNE approach. If the muscle is large, then we sample at intervals of 0.5 cm perpendicular to the motor point.…”