myoclonus vs spasm

myoclonus

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

spasm

noun
  • A sudden, involuntary contraction of a muscle, a group of muscles, or a hollow organ. 

  • A sudden and temporary burst of energy, activity, or emotion. 

  • A violent, excruciating seizure of pain. 

verb
  • To produce and undergo a spasm or series of spasms. 

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