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Chapter 10 - Electromyography (EMG)

Published online by Cambridge University Press:  14 September 2023

John A. Jarratt
Affiliation:
Emeritus, Sheffield Teaching Hospitals NHS Foundation Trust
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Summary

Electromyography is used to differentiate primary muscle disease (myopathy) from abnormalities within the muscle resulting from pathology of its nerve supply (neuropathy). The diagnosis rests on the assessment of motor unit size and an estimate of motor unit numbers during voluntary activity, the recruitment pattern. That motor unit size is reflected in motor unit potential duration is explained and illustrated. Excessive polyphasic motor unit potentials are abnormal but do not, by themselves, distinguish between neuropathy and myopathy. The limitations of assessing motor unit numbers are acknowledged. Potentials may also be recorded from resting muscles. These may be normal as in end-plate potentials or end-plate noise, or abnormal as in fibrillation potentials, positive sharp waves, fasciculation potentials, myotonia, myokymia or complex repetitive discharges. Elegant examples of all of these are included.

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Publisher: Cambridge University Press
Print publication year: 2023

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  • Electromyography (EMG)
  • John A. Jarratt, Emeritus, Sheffield Teaching Hospitals NHS Foundation Trust
  • Book: Essential Electromyography
  • Online publication: 14 September 2023
  • Chapter DOI: https://doi.org/10.1017/9781009381055.011
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  • Electromyography (EMG)
  • John A. Jarratt, Emeritus, Sheffield Teaching Hospitals NHS Foundation Trust
  • Book: Essential Electromyography
  • Online publication: 14 September 2023
  • Chapter DOI: https://doi.org/10.1017/9781009381055.011
Available formats
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Save book to Google Drive

To save content items to your account, please confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account. Find out more about saving content to Google Drive.

  • Electromyography (EMG)
  • John A. Jarratt, Emeritus, Sheffield Teaching Hospitals NHS Foundation Trust
  • Book: Essential Electromyography
  • Online publication: 14 September 2023
  • Chapter DOI: https://doi.org/10.1017/9781009381055.011
Available formats
×