Multiple Sclerosis (MS) is an unpredictable, often disabling disease of the central nervous system that disrupts the flow of information within the brain, and between the brain and body. Multiple Sclerosis (MS) involves an immune-mediated process in which an abnormal response of the body’s immune system is directed against the central nervous system (CNS), which is made up of the brain, spinal cord and optic nerves. The exact antigen — or target that the immune cells are sensitized to attack — remains unknown, which is why MS is considered by many experts to be “immune-mediated” rather than “autoimmune.”
Within the CNS, the immune system attacks myelin — the fatty substance that surrounds and insulates the nerve fibers — as well as the nerve fibers themselves. The damaged myelin forms scar tissue (sclerosis), which gives the disease its name. When any part of the myelin sheath or nerve fiber is damaged or destroyed, nerve impulses traveling to and from the brain and spinal cord are distorted or interrupted, producing a wide variety of symptoms.
The disease of MS is thought to be triggered in a genetically susceptible individual by a combination of one or more environmental factors. People with MS typically experience one of four disease courses, which can be mild, moderate or severe.
There are four types of MS: Relapsing-remitting (RRMS), Secondary-progressive (SPMS), Primary-progressive (PPMS) and Progressive-relapsing (PRMS). The above types are listed in most to least common and are characterized by how the disease progresses. Relapsing-remitting is defined by clearly identifiable attacks of “worsening neurologic function”.
Sometimes these attacks are called relapses, exacerbations or flare-ups and are followed by partial or even complete recovery periods. Around 85% of those with MS are initially diagnosed with relapsing-remitting and most eventually transition to secondary-progressive ms (SPMS). In this stage, MS will progress steadily (not necessarily more quickly) and may or may not be accompanied by relapses.
About 10% of those with MS are diagnosed with Primary-progressive MS (PPMS) which is characterized by the steady worsening of neurologic function with no distinct relapses or remissions. Progressive-relapsing MS (PRMS) is the least common type of MS and is defined by a steady progression from the onset, occasional relapses along the way and may or may not show signs of any recovery. This type of MS progresses without signs of remission.
The disease is progressive, there is no cure and the cause of MS is still unknown.