Disease patterns · Core

Recognize a myopathic pattern

Electrodiagnosis of myopathy

Understand what recruitment and distribution reveal, and what EMG cannot name alone.

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

01Common features

  • Short, low-amplitude MUAPs with early recruitment relative to force may support myopathy.
  • Sensory conduction is usually preserved. Severe myopathy may reduce CMAP amplitude.

02Spontaneous activity

  • Fibrillations, positive sharp waves and myotonic discharges occur in some inflammatory, necrotizing and inherited myopathies.
  • Some myopathies have nearly normal EMG. Spontaneous activity does not automatically indicate neurogenic disease.

03Next information

  • Integrate proximal/distal distribution, CK, medication history, imaging and appropriate genetic or pathological testing.
  • Coordinate biopsy selection to avoid local changes caused by recent needle sampling.

Pause and explain

Explain in your own words: “EMG can support a myopathic pattern but usually cannot name a specific myopathy alone.” Then think of a situation in which it could be misinterpreted.

Show a review prompt

Chronic myopathy and reinnervation can both have complex morphology.

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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.