Multiple sclerosis (MS) is the most common chronic inflammatory disease of the central nervous system and it affects more than 2 million people worldwide (over 400,000 in the U.S.). It is currently incurable. It is characterized by fully or partially reversible episodes of neurologic disability, often lasting days to weeks. Symptoms typically include loss of vision in one eye caused by optic neuritis (inflammation of the optic nerve), limb weakness or numbness (inflammation of spinal nerves), double vision (brainstem dysfunction), and ataxia (wobbly gait due to cerebellar inflammation). After 10 to 20 years, many people with MS develop a progressive course characterized by impaired mobility and cognition while about 15 percent of patients have this progressive course from the onset of the disease. More than a dozen medications are available that reduce the frequency of neurologic flare-ups, however there are no medications that prevent or reverse the progressive neurologic impairment most commonly characterized by impaired mobility, loss of bladder control, and cognitive impairment. The annual economic cost of MS in the U.S. is about $10 billion.
The main consequence of MS is demyelination of nerves. Myelin is a protein that surrounds nerves, much like the plastic insulation on copper electrical wires. When the myelin disappears, the nerves do not function properly. More simply put, the nerves short-circuit similar to bare copper wires touching each other. The demyelination process causes protein build-ups in the central nervous system. These protein build-ups are called plaques and can be seen in the brain and spinal cord by using imaging studies like MRI and CT scans. Sequential scans can follow disease progression. 150 years ago, long before scanning technologies were available, it was recognized that disseminated plaque-like sclerosis was the hallmark of MS. This was discovered by using autopsies to examine the central nervous systems of those who had MS symptoms. In addition, the cerebrospinal fluid (CSF) of those with MS contains abnormal proteins not found in the CSF of people without MS.
Three quarters of those with MS are women, as is common in diseases that are considered autoimmune. The cause of MS is unknown although there is a familial factor. People with a first-degree relative with MS have about a 4 percent risk of developing it and identical twins have a 50 percent risk. There is an environmental factor as well as MS is more common in temperate zones as opposed to tropical zones leading to speculation that Vitamin D from sunlight plays a preventative role. Smoking, obesity, and a history of mononucleosis also lead to an increased risk of MS. Much research into treatment is ongoing with an increased focus on immunotherapies and stem cell transplants. Meaningful advances in immunology, myelin biology, and neuroscience, together with a global focus on halting progressive disability have opened the promise of better understanding of, and therapeutic attack on, multiple sclerosis.
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