Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) spinal and bulbar muscular atrophy ?
    ### Response:
    Spinal and bulbar muscular atrophy, also known as Kennedy disease, is a disorder of specialized nerve cells that control muscle movement (motor neurons). These nerve cells originate in the spinal cord and the part of the brain that is connected to the spinal cord (the brainstem).
    