Macro-EMG and MUNE changes in patients with amyotrophic lateral sclerosis: one-year follow up

OBJECTIVE: We assessed changes in Motor Units (MU) and extent of MU loss using macro-electromyography (macro-EMG) and Motor Unit Number Estimation (MUNE). METHODS: We applied these techniques to a sample of 61 Amyotrophic Lateral Sclerosis (ALS) patients basally (T0) and after 4 (T1), 8 (T2), and 12 (T3) months. Macro Motor Unit Potentials (macro-MUPs) were derived from Biceps Brachii (BB) muscle; MUNE was performed both in BB and Abductor Digiti Minimi (ADM) muscles of the same side. RESULTS: Macro-MUPs area resulted in progressive increase at T1, T2, and T3 with respect to T0. Fiber density (FD) at T3 decreases a bit than at T2. Functioning MUS number decreased in both the muscles throughout the entire follow-up with respect to T0 and the rate of MU decrease was similar in both the muscles, but steeper distally. CONCLUSIONS AND SIGNIFICANCE: Macro-EMG increase and FD decrease suggest that a process of MU rearrangement begins to fall after 8 months of disease course. Combined use of macro-EMG and MUNE techniques in ALS patients allows to track over time changes in muscle MU features and number in face of progressive anterior horn cells death during disease's evolution.