Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) multiple sclerosis ?
    ### Response:
    Multiple sclerosis is a condition characterized by areas of damage (lesions) on the brain and spinal cord. These lesions are associated with destruction of the covering that protects nerves and promotes the efficient transmission of nerve impulses (the myelin sheath) and damage to nerve cells.
    