Motor Unit Number Estimation (Mune) as a Quantitative Measure of Disease Progression and Motor Unit Reorganization in Amyotrophic Lateral Sclerosis

Motor Unit Number Estimation (MUNE), a technique allowing to estimate the number of functioning Motor Units (MU) in single muscles, was used to score the disease's severity and progression rate in a group of 58 patients with Amyotrophic Lateral Sclerosis (ALS). All patients underwent MUNE in the abductor digiti minimi (ADM) muscle during the diagnostic work-up (T0), after three (T1) and six (T2) months. A significant loss [p < .001] of MU and a decrease [p < .001] of the maximal M wave area at T0 was found, whereas mean step area was increased [p < .001]. During the follow-up (T1 and T2), MU loss continued, maximal M wave decreased, and mean step area increased significantly. The results confirm that MUNE is a suitable tool to quantify the pathological changes in MU in patients with ALS.