Multiple sclerosis (MS) is a chronic disease that affects the brain and spinal cord. MS can cause a variety of symptoms, including changes in sensation, visual problems, muscle weakness, depression, and difficulties with coordination and speech. Although many patients lead full and rewarding lives, MS can cause impaired mobility and disability in the more severe cases.
Multiple sclerosis affects neurons, the cells of the brain and spinal cord that carry information, create thought and perception and allow the brain to control the body. Surrounding and protecting these neurons is a fatty layer known as the myelin sheath, which helps neurons carry electrical signals. MS causes gradual destruction of myelin (demyelination) and transection of neuron axons in patches throughout the brain and spinal cord, causing various symptoms depending upon which signals are interrupted. The name multiple sclerosis refers to the multiple scars (or scleroses) on the myelin sheaths. It is thought that MS results from attacks by an individual’s immune system on the nervous system and is therefore categorized as an autoimmune disease.
Multiple sclerosis may take several different forms, with new symptoms occurring in discrete attacks or slowly accruing over time. Between attacks, symptoms may resolve completely, but permanent neurologic problems often persist. Although much is known about how MS causes damage, its exact cause remains unknown. MS currently does not have a cure, though several treatments are available which may slow the appearance of new symptoms. MS primarily affects adults, with an age of onset typically between 20 and 40 years, and is more common in women than in men.