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Laboratory Reference for Clinical Neurophysiology$
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Jay A. Liveson and Dong M. Ma

Print publication date: 1999

Print ISBN-13: 9780195129243

Published to Oxford Scholarship Online: March 2012

DOI: 10.1093/acprof:oso/9780195129243.001.0001

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Motor Unit Potential Studies

Motor Unit Potential Studies

(p.408) Chapter 23 Motor Unit Potential Studies
Laboratory Reference for Clinical Neurophysiology

Jay A. Liveson

Dong M. Ma

Oxford University Press

The discharge of an anterior horn cell causes an action potential to travel down its axon, producing an almost synchronous depolarization of the muscle fibers it innervates. This physiologic unit is the motor unit and the summated potential generated is the motor unit potential (MUP) or motor unit action potential. The first section of this chapter addresses the values of MUPs available in the literature. The values are classified by the type of needle used (concentric versus monopolar), then by the age of the subject. Values of specific muscles are given for the duration, amplitude, and percentage of polyphasia, which reflects configuration. In general, the MUPs in myopathies are of short duration, low amplitude, and possibly polyphasic configuration. This pattern is thought to reflect loss of muscle fibers. In contrast, in neuropathic processes, the MUPs are of long duration. This is thought to result from increased temporal dispersion in terminal nerve fibers.

Keywords:   anterior horn cell, depolarization, motor unit potential, motor unit action potential, polyphasia, temporal dispersion, myopathies

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