Electromyography

Needle recording of the electrical activity of skeletal muscle at rest and during voluntary contraction. After nerve injury it shows fibrillation potentials from denervated fibres (from one to four weeks), the loss or return of voluntary motor units and reinnervation potentials, complementing nerve conduction studies in localising the lesion and quantifying axon loss.

Related terms

• Investigation

  Nerve conduction studies

  Electrodiagnostic investigation that measures distal motor latency, sensory nerve action potential amplitude, and conduction velocity along peripheral nerves. In carpal tunnel syndrome, prolonged distal motor latency and reduced sensory nerve action potential amplitude define disease severity.

• Investigation

  Fibrillation potentials

  Spontaneous electrical discharges of individual denervated muscle fibres recorded on needle electromyography. They appear one to four weeks after an axonal nerve injury, later for proximal lesions, and their amplitude declines over the following year, which helps date an injury of uncertain age.

Articles mentioning this term

1. FESSH preparation · 26 September 2026

   Peripheral nerve injury and repair

   Peripheral nerve injury for FESSH candidates: degeneration, Seddon and Sunderland grades, electrodiagnosis, timing, grafts, conduits and nerve transfers.

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