Multiple sclerosis is a chronic and disabling disease in which the body's immune response attacks a person's central nervous system, especially the spinal cord and brain. This leads to the demyelination of axons, which transmit the nerve impulses from the neuron body to the dentrites of another. Thus, multiple sclerosis impairs the ability of neurons (nerve cells) in the brain and spinal cord to link up with each other. Neurons communicate with each other via nerve impulses, or electrical signals, through fibers called axons, which are enveloped in a fatty insulating substance called myelin. In multiple sclerosis, the body's own immune system attacks and destroy the myelin, impairing the axons from effiently transmitting these electrical signals.
The term multiple sclerosis refers to scars (scleroses—better known as plaques or lesions) in the white matter of the brain and spinal cord, which is mainly composed of myelin. Although much is known about the mechanisms involved in the disease process, the cause remains unknown. Theories include genetics or infections. Different environmental risk factors have also been found.
The symptoms of this disease may be mild, like numbness in the limbs, or severe, such as paralysis or loss of vision. The progress, severity, and specific symptoms of multiple sclerosis are unpredictable and vary from one person to another. But almost any neurological symptom can appear with the disease; as it progresses, physical and cognitive disability and neuropsychiatric disorder might appear. Disease onset usually occurs in young adults, and it is more common in females.
Although the cause of multiple sclerosis is still not known, scientists believe that it is caused by a combination of several factors. Presently scientists are doing research in the areas of immunology and genetics in an effort to find the cause of the disease. But it is now generally accepted that multiple esclerosis involves an autoimmune process, which is an abnormal response of the body’s immune system that is directed against the myelin in the central nervous system, such as the brain, spinal cord and optic nerves. The exact antigen, or target that the immune cells are sensitized to attack, remains unknown.