Multiple Sclerosis explained

Multiple sclerosis (MS) is a chronic, sometimes disabling, disease of the central nervous system affecting an estimated 2.5 million people worldwide. In the UK, about one per 1,000 of the population is affected by MS. It affects twice as many women as men. It is principally a disease of young people, with an average age of onset around 30 years of age.

In multiple sclerosis, the myelin sheath - the fatty insulation surrounding nerve cells in the brain and spinal cord - becomes inflamed. Myelin, which acts like the rubber insulation found in an electric cable, facilitates the smooth transmission of high-speed messages between the brain and the spinal cord and the rest of the body. As areas of myelin are affected, messages are not sent efficiently or never get through.

Eventually there is a build-up of scar tissue (sclerosis) in multiple places; hence the disease is termed multiple sclerosis. These plaques or scarred areas, which are only a fraction of inch in diameter, can interfere with signal transmission. The underlying nerve may also be damaged, further worsening symptoms and reducing the degree of recovery experienced. The disease can manifest itself in many different ways. Sometimes the diseased areas cause no apparent symptoms and sometimes they cause many; this is why the severity of problems varies greatly among persons affected with MS.

Misguided attack
MS is classified as an autoimmune disease. In MS, the immune system - for reasons still not understood - attacks and destroys myelin and the oligodendrocytes (oligo-few, dendro-branches, cytes-cells) that produce it. Certain types of white blood cells called T-lymphocytes and killer T-cells appear to attack and consume myelin. Though the body usually sends in immune cells to fight off bacteria and viruses, in MS they misguidedly attack the body's own healthy nervous system, thus the term autoimmune disease. MS is similar to other autoimmune conditions such as rheumatoid arthritis and lupus. Multiple sclerosis usually strikes in the form of attacks or exacerbations. This is when at least one symptom occurs, or worsens, for more than 24 hours. The symptom(s) can last for days, weeks, months, or indefinitely.