Cortical versus spinal dysfunction in amyotrophic lateral sclerosis

• Published in: Muscle & nerve Vol. 33; no. 5; pp. 677 - 690
• Main Authors: Attarian, Shahram, Vedel, Jean-Pierre, Pouget, Jean, Schmied, Annie
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc., A Wiley Company 01.05.2006; Wiley
• Subjects: Adolescent; Adult; amyotrophic lateral sclerosis; Amyotrophic Lateral Sclerosis - complications; Amyotrophic Lateral Sclerosis - physiopathology; Axons - pathology; Biological and medical sciences; Case-Control Studies; Degenerative and inherited degenerative diseases of the nervous system. Leukodystrophies. Prion diseases; Evoked Potentials, Motor - physiology; Evoked Potentials, Motor - radiation effects; Female; Humans; Kennedy's disease; Male; Medical sciences; Motor Cortex - pathology; Motor Cortex - physiopathology; Motor Neurons - pathology; motor unit; Muscular Atrophy, Spinal - physiopathology; Myography - methods; Neurology; Regression Analysis; Spinal Diseases - etiology; Time Factors; transcranial magnetic stimulation; Transcranial Magnetic Stimulation - methods; Human; Nervous system diseases; Transcranial magnetic stimulation; Variability; Discharge pattern; Electrophysiology; Axon; Amyotrophic lateral sclerosis; Motor neuron; Electromechanical coupling; Motor unit; Kennedy's disease; Dysfunction; Central nervous system disease; Degenerative disease; Spinal cord disease
• ISSN: 0148-639X; 1097-4598
• DOI: 10.1002/mus.20519

Little is known about the possible link between cortical and spinal motor neuron dysfunction in amyotrophic lateral sclerosis (ALS). We correlated the characteristics of the responses to transcranial magnetic stimulation (TMS) with the electromechanical properties and firing pattern of single motor units (MUs) tested in nine ALS patients, three patients with Kennedy's disease, and 15 healthy subjects. In Kennedy's disease, 19 of 22 MUs were markedly enlarged with good electromechanical coupling and discharged with great variability. Their excitatory responses increased with MU size. In ALS, 17 of 34 MUs with excitatory responses behaved as in Kennedy's disease. By contrast, 28 MUs with nonsignificant responses showed poor electromechanical coupling and high firing rates, whereas 28 MUs with inhibitory responses showed moderate functional alterations. This result indicates that in ALS as in Kennedy's disease, sprouting of corticospinal axons may occur on surviving motoneurons. A clear relationship exists between the responsiveness of MUs to TMS and their functional state. Muscle Nerve, 2006