Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Dystonia 8 ?
    ### Response:
    Paroxysmal nonkinesigenic dyskinesia is a disorder of the nervous system that causes periods of involuntary movement. Common symptoms include 1 to 4 hour long episodes of irregular, jerking or shaking movements, prolonged contraction of muscles, chorea, and/or writhing movements of the limb.
    