Electrodiagnostic Assessment of Motor Neuron Disease.

Motor neuron diseases involve degeneration of motor neurons in the brain (upper motor neurons), brain stem, and spinal cord (lower motor neurons). Symptoms vary depending on the degree of upper and lower neuron involvement, but progressive painless weakness is the predominant complaint. Motor neuron disease includes numerous specific disorders, including amyotrophic lateral sclerosis, spinal muscular atrophy, spinal bulbar muscular atrophy, and other inherited and acquired conditions. Abnormalities on nerve conduction studies, repetitive nerve stimulation, needle electromyography, and other electrodiagnostic techniques help to distinguish these disorders from each other, and from other disorders with progressive weakness.