Myoclonus

Myoclonus is the shock-like contraction of a muscle or a group of muscles. Often contractions occur symmetrically in muscles on opposite sides of the body.

Likely causes depend on whether the myoclonus is generalised, or focal and localised to one part of the body:

• generalised myoclonus:
  • certain encephalopathies, e.g. occurring in metabolic disorders, encephalitis lethargica
  • epilepsy
  • benign essential myoclonus: this condition may be autosomal dominant and may have an onset in childhood.
    
    
• focal myoclonus:
  • viral myelitis
  • rarely, if disruption of the deep nuclear connections of the cerebellum