Invited review: electrodiagnostic assessment and monitoring of motor unit changes in disease.

The motor unit characteristics change dynamically with disease. This is the basis for the use of neurophysiologic methods for diagnostic purposes and for long-term monitoring. A great variety of nerve conduction and EMG parameters are available to study the motor unit. They reflect different aspects of motor unit function. Therefore, the electromyographer must choose his technique and optimal parameters depending on the situation, type of condition, whether the purpose is diagnosis or monitoring, and so on. In this presentation the relationship between EMG parameters and physiologic and morphologic counterparts in some pathologic conditions will be discussed.