Complex Repetitive Discharges (CRDs)
- General description
- Complex of muscle fiber action potentials
- Firing pattern: Repeated, Regular
- Onset or Cessation: Abrupt
- Features: Discharges of individual, and groups of, muscle fibers
- Origin: Muscle fibers
- Groups (Neighboring fibers)
- Membranes have lower threshold for generating recurring action potentials
- Activated ephaptically: From muscle fiber to muscle fiber
- Other properties
- Time linked
- May be recurrent
- Persist with neurmuscular junction blockade
- Onset
- Stimulus: Spontaneous or with Muscle irritation
- Firing Rate
- Range: 5 to 150 Hz
- Most common frequencies: 30 to 40 Hz
- More consistent during burst than myotonia
- Patterns
- Usual: Firing in a regular pattern
- Occasional: Abrupt change in frequency; Irregular firing
- Abrupt onset & end
- Non-rhythmic bursts
- Single fiber EMG: Low jitter
- Associations
- Usual: Occur in presence of other EMG abnormalities
- Few patients: Only abnormality on EMG
1
- Muscle involvement
- Legs: Tensor fasciae latae, Gluteus maximus
- Arms: Biceps brachii, Pronator teres
- Associated lesions: L5; C6
- Clinical syndrome: Pain, radicular or limb
- Pathologic associations
- Chronic partial denervation: Grouped atrophy of muscle fibers,
Large & Small
- Plexopathy or Radiculopathy
- Spinal muscular atrophy
- Motor neuron disease
- Not common in: Mononeuropathy; Acute disorders
- Myopathies
- May produce muscle hypertrophy: Unilateral or Asymmetric
- Pharmacology: Corticosteroids may suppress CRDs
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