hyperkinesis vs myoclonus

hyperkinesis

noun
  • Abnormally increased and sometimes uncontrollable activity or muscular movements. 

  • A condition especially of childhood characterized by hyperactivity. 

myoclonus

noun
  • The brief, involuntary twitching of a muscle or group of muscles. 

How often have the words hyperkinesis and myoclonus occurred in a corpus of books? (source: Google Ngram Viewer )