Needle EMG · Advanced

Myotonia and peripheral nerve hyperexcitability

Myotonic vs neuromyotonic discharges

Similar names can describe activity from different physiological sources.

3 learning sectionsCompiled 2026-09-08English edition · Traditional Chinese available

01Myotonic discharges

  • Repetitive muscle-fiber activity often waxes and wanes in frequency and amplitude.
  • It occurs in myotonic disorders and other myopathies; clinical delayed relaxation is not always present.

02Neuromyotonia and myokymia

  • Neuromyotonic activity consists of high-frequency motor-unit trains, often with declining frequency or amplitude.
  • Myokymia consists of grouped motor-unit discharges. Interpret the distribution and clinical context.

03Differentiation

  • CRDs tend to repeat a fixed complex with abrupt onset and offset. Sound analogies alone are insufficient.
  • Associated neurogenic or myopathic features guide etiology better than the discharge name alone.

Pause and explain

Explain in your own words: “Ask whether a single muscle fiber or a whole motor unit is firing.” Then think of a situation in which it could be misinterpreted.

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References and further reading

Educational synthesis; independent neuromuscular specialist review is pending. Publication dates and compilation dates are distinct. This is an original teaching synthesis; consult the source for complete methods and criteria.