Commonly observed or notable abnormal spontaneous activity
| Term | Description | Clinical significance |
|---|---|---|
| Fibrillation potentials and positive sharp waves | Spontaneous muscle fiber potentials recorded during rest; morphology and firing regularity determine categorization as fibrillation potentials or positive sharp waves | Muscle fibers are remaining without innervation, generally a sign of recent or ongoing denervation in neurogenic conditions In myopathic conditions, they may indicate inflammatory or necrotizing myopathies |
| Fasciculation potentials | Spontaneous, irregularly firing motor unit discharges | May be seen occasionally in chronic neurogenic conditions of any kind, but are seen more diffusely in disorders of the anterior horn cell and motor neuron disease |
| Myotonic discharges | Single muscle fiber firing repetitively in a waxing andwaning pattern at high frequency | When diffuse and prominent, indicates a myotonic disorder Can also rarely be seen in any chronic neurogenic or myopathic condition |
| Complex repetitive discharges | Time-locked repetitive firing of a group of muscle fibers, with sudden start and stop of bursts | Very chronic neurogenic or myopathic conditions |
| Neuromyotonic discharges | Single motor unit firing repetitively at a very high frequency | Typically, disorders of voltage-gated potassium channels |
| Myokymic discharges | Single motor unit firing in regularly recurring bursts | Most commonly associated with chronic demyelination and radiation plexopathy |