Multiple Sclerosis Multiple sclerosis (MS) is an unpredictable, chronic disease of the central nervous system. Some people with MS may be mildly affected, but others may lose their ability to write, speak, or walk. Primary Progressive Multiple Sclerosis Multiple sclerosis (MS) is a disease that interferes with your brain's ability to operate your body. Relapsing-Remitting Multiple Sclerosis People who have relapsing-remitting MS have flare-ups of the disease, or relapses. Between these flare-ups, people have periods of recovery, or remissions. Optic Neuritis Optic neuritis is a condition that affects the eye and your vision, and occurs when the optic nerve is inflamed. Multiple Sclerosis and Pregnancy Pregnancy does not appear to speed up the course or worsen the effects of MS. Some studies have found that MS symptoms decrease in pregnancy and increase after delivery.