The reorganization of motor units in motor neuron disease

• Published in: Muscle & nerve Vol. 20; no. 3; pp. 306 - 315
• Main Authors: Emeryk-Szajewska, Barbara, Kopeć, Jerzy, Karwanska, Anna
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc., A Wiley Company 01.03.1997; Wiley
• Subjects: Action Potentials; Adaptation, Physiological; Adolescent; Adult; Aged; amyotrophic lateral sclerosis; Biological and medical sciences; concentric needle electromyography; Degenerative and inherited degenerative diseases of the nervous system. Leukodystrophies. Prion diseases; Electromyography; Female; Humans; Male; Medical sciences; Middle Aged; motor neuron disease; Motor Neuron Disease - physiopathology; Motor Neurons - physiology; Nerve Degeneration; Nerve Regeneration; Neurology; recruitment order; Reference Values; reinnervation; Human; Nervous system diseases; Pathophysiology; Motor neuron disease; Action potential; Amyotrophic lateral sclerosis; Striated muscle; Motor unit; Genetic disease; Recruitment; Electrodiagnosis; Central nervous system disease; Degenerative disease; Electromyography; Reinnervation; Spinal cord disease
• ISSN: 0148-639X; 1097-4598
• DOI: 10.1002/(SICI)1097-4598(199703)20:3<306::AID-MUS7>3.0.CO;2-F

We studied 78 patients with motor neuron disease (MND) using concentric needle electromyography. Analysis on weak and maximal effort was performed using our own, fully automated, computer method, EMG‐LAB. In addition to the conventional parameters of single motor unit action potentials (MUAPs) and interference pattern, new criteria were applied: the range of the acting motor units and the functional recruitment order. A total of 375 muscles of MND patients and 120 control muscles were investigated. The electromyographic data were analyzed separately in five groups of muscles, classified A, B, C, D, and E according to their clinical condition. Those results allowed us to discern six neurophysiological stages (N 0, 1, 2, 3, 4, 5) from the early to the most advanced phase. It has been confirmed that reinnervation in MND is adequate to compensate for the loss of over 50% of motor neurons but it is only a transitory phase in the morbid course. At stages N0–5, the electrophysiological data reflect structural and functional integrity of the functioning motor units. Evaluation of not only single MUAPs but also of the full range of acting motor units and their recruitment order allowed a deeper look into the underlying pathophysiological mechanisms. © 1997 John Wiley & Sons, Inc. Muscle Nerve, 20, 306–315, 1997.