Multiple sclerosis (MS) is an autoimmune disease that causes your immune system to attack myelin in your nerves. Myelin is an insulating sheath that protects the axon, which is the part of a neuron responsible for transmitting electrical signals throughout your nervous system. When myelin is damaged, these signals become disrupted, leading to symptoms that can affect the functions of your spinal cord, brain, and eyes.
Multiple sclerosis may affect your vision at first; in fact, optic neuritis can often be a warning sign of MS. Other symptoms include fatigue, loss of coordination, muscle spasms or weakness, tingling, and numbness. When someone experiences an initial episode of multiple sclerosis symptoms, they may initially be diagnosed with clinically isolated syndrome (CIS). Not everyone who receives this diagnosis necessarily develops MS.
People who are diagnosed with MS typically have relapsing-remitting MS (RRMS), in which symptoms periodically flare up; this can later become secondary progressive MS (SPMS), in which symptoms are more constant due to cumulative nerve damage, though flare-ups can still occur. Some people diagnosed with MS have primary progressive MS (PPMS), in which symptoms are constant and gradually worsen over time without flare-ups.
