Below is an instruction from Human. Write a response.
    ### Instruction:
    How to diagnose Alzheimer's Disease ?
    ### Response:
    The only definitive way to diagnose Alzheimer's disease is to find out whether plaques and tangles exist in brain tissue. To look at brain tissue, doctors perform a brain autopsy, an examination of the brain done after a person dies. Doctors can only make a diagnosis of "possible" or probable Alzheimers disease while a person is alive.
    