Chapter 14 Motor unit number estimation (MUNE) with nerve conduction studies

Publisher Summary Motor unit number estimates (MUNE) provide a quantitative measure of the number of motor units in a muscle or group of muscles by comparing the size of the surface recorded, single motor unit potentials (SMUP) with the compound muscle action potential (CMAP). If there are only a few motor units making up the CMAP, the single motor unit potentials can be counted individually with graded stimuli that activate individual units in an all-or-none fashion. When there are more than a few SMUP, a sample of SMUP is used to estimate the size of all the SMUP. A number of methods have been developed to estimate the size of SMUP. They vary in their approach and to some extent in their ease of application, but give comparable values for MUNE in individual muscle groups. The size and shape of both the compound muscle action potential and single motor unit potentials are a function of the location of the recording electrodes. The combination of MUNE with the tracking of SMUP has provided an additional tool for measuring the physiologic natural history of changes in the number and physiology of motor units.