Dear Dr. Roach: I was diagnosed with relapsing-remitting multiple sclerosis (RRMS) at the age of 46. The course of the disease was mild for me with only three identifiable MS attacks (in both my spine and brain). Although I initially resisted treatment, I took Copaxone shots for seven years before my neurologist believed that it was safe to discontinue treatment. Since this time, I haven’t had any new attacks, only some occasional balance issues and lingering weakness in my left leg.

My concern is secondary progressive MS (SPMS) and the possible consequences of an occurrence. I’ve recently read about therapeutic plasma exchange as a disease prevention option. It’s an extremely expensive treatment, so I’m curious about your thoughts regarding its effectiveness for the possible prevention of SPMS. — S.G.

Answer: MS is a disease where the immune system attacks the myelin coating that protects the nerves in the brain and spinal cord. There are different patterns of disease activity, with RRMS being the most common.

People (much more often women) have acute attacks of symptoms that stop, and a person recovers partially or completely until the next flare-up. The major symptoms of MS include sensory changes in the limbs, visual loss or double vision, gait changes, weakness, and bladder problems, although there are many other symptoms that any given person with MS might have.

Primary progressive MS (PPMS) only represents about 10% of MS cases and is equally likely to happen to men or women. In these cases, the disease is progressive, although there may be some relapses or temporary minor improvements. Some people who initially have RRMS will eventually convert to progressive MS, most commonly about 10 years after their diagnosis.

I completely understand why you’d be interested in treatments that might reduce your risk of developing secondary progressive MS, as this has a worse prognosis. Plasma exchange is useful for acute relapses in symptoms, but unfortunately, the data on plasma exchange don’t show effectiveness at preventing the conversion of RRMS to SPMS.

Therapies that have been proven to reduce the conversion to SPMS include the medication that your neurologist prescribed you — glatiramer acetate (Copaxone). The most effective treatments were fingolimod (Gilenya and others), natalizumab (Tysabri), and alemtuzumab (Lemtrada).