Cortical versus spinal dysfunction in amyotrophic lateral sclerosis.
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.
Attarian
Shahram
S
Department of Neurology and Neuromuscular Diseases, CHU La Timone, 264 rue Saint-Pierre, 13385 Marseille, France. sattarian@@ap-hm.fr
Vedel
Jean-Pierre
JP
Pouget
Jean
J
Schmied
Annie
A
D000293:Adolescent; D000328:Adult; D000690:Amyotrophic Lateral Sclerosis / Q000150:complications* / Q000503:physiopathology*; D001369:Axons / Q000473:pathology; D016022:Case-Control Studies; D019054:Evoked Potentials, Motor / Q000502:physiology / Q000528:radiation effects; D005260:Female; D006801:Humans; D008297:Male; D009044:Motor Cortex / Q000473:pathology / Q000503:physiopathology*; D009046:Motor Neurons / Q000473:pathology; D009134:Muscular Atrophy, Spinal / Q000503:physiopathology; D009213:Myography / Q000379:methods; D012044:Regression Analysis; D013122:Spinal Diseases / Q000209:etiology*; D013997:Time Factors; D050781:Transcranial Magnetic Stimulation / Q000379:methods