Fibre density, amplitudes of macro-EMG motor unit potentials and conventional EMG recordings from the anterior tibial muscle in patients with amyotrophic lateral sclerosis. A study on 51 cases.

Fibre density and amplitudes of macro-EMG motor unit potentials were studied and compared with conventional EMG in the anterior tibial muscles from 51 patients with amyotrophic lateral sclerosis. The fibre density was increased in 46 muscles. Increased amplitudes of macro-EMG motor unit action potentials were found in 46 muscles, while the mean duration of motor unit potentials recorded with a concentric needle electrode was prolonged in only 26 muscles. Changes in the packing density of muscle fibres of surviving motor units are thought to influence the different electrophysiological parameters in different ways.