Pilot study: quantification of motor unit stability, or “jiggle”, in amyotrophic lateral sclerosis (731.11)

Abstract

Loss of motor units (MUs) have been found in aging, neuropathies, and motor neuron diseases. With MU loss, subsequent collateral reinnervation results in unstable motor unit potentials (MUPs) with variability in firing times and generation of muscle fiber action potentials. Jiggle is a measure of MUP stability, which can be calculated using Decomposition‐based Quantitative Electromyography (DQEMG). Two previous studies have attempted to measure jiggle, but both studies were limited by the EMG decomposition algorithms used. The purpose of this study is to measure jiggle in the upper trapezius muscle of 11 amyotrophic lateral sclerosis (ALS) patients compared to age‐matched healthy controls. Jiggle will be calculated using the normalized value of the median consecutive amplitude difference (CAD). Jiggle will also be compared to other MUP parameters including motor unit number estimation (MUNE), mean surface MUP (S‐MUP) size, MUP amplitude, and near fiber count. As a result of denervation and incomplete reinnervation, we expect to see significantly higher jiggle values in patients with ALS relative to controls. We also expect jiggle to be negatively correlated with MUNE, and positively correlated with mean S‐MUP size, MUP amplitude, and near fiber count. If successful, jiggle may be a valuable diagnostic parameter or outcome measure in age‐related sarcopenia, neuropathies, or motor neuron diseases such as ALS.