Multiple Sclerosis (MS) Both mutliple sclerosis and Guillain-Barre Syndrome are diseases that cause demyelination of the nerves; however, the demyelination in the condition of Multiple Sclerosis occurs in CNS (central nervous system), like in the brain and spinal cord, while in the condition of Guillain-Barre Syndrome, the demylination occurs in the peripheral nervous system; such as in the limbs and skin!