Multiple sclerosis (MS) is an autoimmune disease in which the body’s own immune cells mistakenly attack and damage the myelin sheath, the fatty covering that surrounds and protects nerve cells in the brain and spinal cord. Loss of myelin, referred to as demyelination, interferes with the transmission of nerve signals and triggers a wide range of unpredictable symptoms, including blurred vision, loss of balance, poor coordination, slurred speech, tremors, numbness, extreme fatigue, problems with memory and concentration, paralysis, stiffness, bladder problems and blindness. Fever, hot baths, sun exposure, and stress can trigger or worsen attacks
MS can be diagnosed at any age, but is most commonly diagnosed between ages 20 and 40 and affects women more than men. The cause of MS is unknown, but viruses, gene defects and environmental factors may all play a role. It affects more than 400,000 people in the U.S. and 2.5 million worldwide.
There is no cure at present, but multiple medications now on the market slow progression and help control symptoms. Promising therapies being developed include stem cell therapies that may halt the autoimmune process and regenerate myelin.
Several subtypes, or patterns of progression, have been described. Subtypes use the past course of the disease in an attempt to predict the future course. They are important not only for prognosis but also for therapeutic decisions. In 1996 the United States National MS Society standardized four subtype definitions:
- Relapsing Remitting
Relapsing-remitting MS is characterized by unpredictable relapses (attacks) followed by periods of months to years of relative quiet (remission) with no new signs of disease activity. Loss of function suffered during attacks may either resolve or result in some disability (deficit), the latter being more common as a function of time. This describes the initial course of 80% of individuals with MS. When deficits always resolve between attacks, this is sometimes referred to as benign MS, although patients will still accrue some degree of disability in the long term.
- Secondary Progressive
Secondary progressive MS (sometimes called “galloping MS”) develops in about 65% of those patients initially diagnosed with relapsing-remitting MS. Progressive neurological decline occurs between acute attacks without any definite periods of remission, although minor remissions may appear. The median time between disease onset and conversion from relapsing-remitting to secondary progressive MS is about 19 years.
- Primary Progressive
Primary progressive MS describes the approximately 10 –15% of individuals who never experience remission after their initial MS symptoms. It is characterized by progression of disability from onset, with no, or only occasional and minor, remissions and improvements. The age of onset for primary progressive MS is later than for the relapsing-remitting, generally around age 40.
- Progressive Relapsing
Progressive relapsing MS describes those individuals who experience steady neurologic decline from the beginning, but also suffer clear superimposed attacks. This is the least common of all subtypes.
Nearly 4% of the world’s population is affected by one of more than 80 different autoimmune diseases, the most common of which include type 1 diabetes, multiple sclerosis, rheumatoid arthritis, lupus, Crohn’s disease, psoriasis and scleroderma.