The electrophysiology of the motor neuron diseases.

The motor neuron diseases are a set of disorders associated with the selective degeneration of motor neurons. Amyotrophic lateral sclerosis (ALS) is the most common and confers the gravest prognosis. Although ALS occurs with known genetic causes in a small minority, other motor neuron disorders have well-defined genetic mutations. Electrodiagnostic testing is important to distinguish these various disorders. Electrodiagnostic testing is also crucial for distinguishing potential mimic syndromes, such as multifocal motor neuropathy and inclusion body myositis. Newer neurophysiology techniques have been developed in the past several years. What role these techniques will play in clinical practice is currently unknown.