Complex Repetitive Discharges

Sweep speed = 10 ms/div; Sensitivity = 0.1mV/div
Bursts of recurrently firing complex muscle action potentials
  • Discharges of individual, and groups of, muscle fibers
    • Origin: Muscle fiber groups
    • Activated ephaptically: From muscle fiber to muscle fiber
    • Time linked
    • May be recurrent
    • Persist with neurmuscular junction blockade
    • Onset
      • Stimulus: Spontaneous or with Muscle irritation
    • 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
      • Rarely or never the only abnormality on EMG
  • 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
from M. Al-Lozi

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