By Charles Smith, MD, Scripps Health
Multiple sclerosis is a chronic autoimmune disease that disrupts nerve impulses in the central nervous system (brain, optic nerves and spinal cord) by attacking the protective coverings around nerve fibers known as myelin, and often damaging the nerve fibers (axons) themselves. Consequently, it can cause a diverse range of symptoms including numbness, weakness, spasticity, gait disturbances, bladder problems, cognitive and memory problems, speech disorders, vision problems and others.
Often referred to simply as MS, multiple sclerosis is believed to affect more than 2.5 million people worldwide, including approximately 400,000 people in the U.S. Another 200 are newly diagnosed in the U.S. every week. It is three times more common in women than men, and is most often diagnosed between the ages of 20 and 50, although rarely has it been shown to affect infants and elderly people.
The cause of MS is unknown, but genetics and environmental factors may influence its onset. Though it is not directly inherited from a parent, the risk of developing MS is greater in people who have a close relative, such as a parent or sibling, with the disease. It is more common among Caucasians than other ethnic groups. Because women are affected more often than men, researchers are studying whether hormones may play a role. Worldwide, MS is more common in areas farther from the equator, which has led researchers to conclude that exposure to sunlight and low vitamin D levels influence the development of MS. Another confirmed environmental factor is smoking.
Most researchers believe the disease is triggered by exposure to a virus — Epstein Barr virus is the current leading candidate — but proof is not yet available.
MS is often not diagnosed right away because so many of its symptoms may be caused by other conditions. In most cases, a neurologist will diagnose the disease after a thorough physical examination and a brain MRI, which will reveal abnormalities on the brain. Lumbar puncture (spinal tap) is often included in the work up to confirm that the diagnosis is indeed MS.
Once treatment is initiated, a brain MRI is usually done annually to ensure treatment is maximally effective.
Because MS is most frequently an episodic disease, patients experience relapses and remissions, and symptoms can vary from one episode to the next. Major symptoms may disappear completely between relapses. In severe cases, symptoms such as speech or vision problems or paralysis may become permanent.
Treatment focuses on relieving symptoms and reducing the frequency of relapses and preventing disability. Historically, MS patients who receive no treatment have had an average of about one relapse (exacerbation) per year. New treatments discovered over the past two decades have shown significant progress in reducing the relapse rate and disability progression. Moreover, the earlier treatment is started, the more effective it may be. The first drugs approved for MS were immunomodulators. These so-called “platform drugs” for MS were approved in the 1990s and include interferons, such as Betaseron, Avonex and Rebif. Copaxone, another platform treatment, is in a separate class.