Below is an instruction from Human. Write a response.
    ### Instruction:
    What are the symptoms of Primary lateral sclerosis ?
    ### Response:
    What are the signs and symptoms of Primary lateral sclerosis? Primary lateral sclerosis (PLS) causes weakness in the voluntary muscles, such as those used to control the legs, arms and tongue. PLS can happen at any age, but it is more common after age 40. A subtype of PLS, known as juvenile primary lateral sclerosis, begins in early childhood.
    