Multiple Sclerosis Health Article

Definition

Multiple sclerosis is an inflammatory demyelinating disease of the central nervous system. The disease results in injury to the myelin sheath (the fatty matter that covers the axons of the nerve cells), the oligodendrocytes (the cells that produce myelin) and, to a lesser extent, the axons and nerve cells themselves. The symptoms of multiple sclerosis vary, depending in part on the location of plaques (areas of thick scar tissue) within the central nervous system. Common symptoms include weakness and fatigue, sensory disturbances in the limbs, bladder or bowel dysfunction, problems with sexual function, and ataxia (loss of coordination). Although the disease may not be cured or prevented at this time, treatments are available to reduce severity and delay progression.

Description

Multiple, or disseminated, sclerosis (MS) is a slowly progressive disease of the central nervous system (CNS), that comprises the brain and spinal cord. In 1868, French physician Jean-Martin Charcot (1825–1893) produced his lectures on "Sclerose en plaques," providing the first detailed clinical description of the disease. The cause of multiple sclerosis is unknown, and it cannot be prevented or cured. Great progress, however, is being made in treating and identifying underlying mechanisms that trigger the disease. The primary characteristic of MS is the destruction of myelin, a fatty insulation covering the nerve fibers. The end results of this process, called demyelination, are multiple patches of hard, scarred tissue called plaques. Another important feature in the disease is destruction of axons, the long filaments that carry electric impulses away from a nerve cell, which is now considered to be a major factor in the permanent disability that occurs with MS.

Multiple sclerosis is usually characterized by a relapsing remitting course in the early stages, with full or nearly full recovery initially. In the early stages, there may be little damage to axons. Over time, the disease enters an irreversible progressive phase of neurological deficit. Each relapse causes further loss of nervous tissue and progressive dysfunction. In some cases there may be chronic progression without remission or acute disease rapidly leading to death.

MS is a diverse disease. No two affected persons are the same and each will experience different combinations of symptoms with differing severity. The most common form is relapsing-remitting multiple sclerosis (RRMS), which affects 80–85% of people with MS. These patients develop disease relapses, often without a specific trigger, but possibly associated with infections. Disease relapses can last between 24 hours and several months, and the person may, or may not, completely recover. The disease is stable between relapses, although affected persons can have residual symptoms and disability.

After several years, the majority (70%) of persons with MS will develop secondary progressive multiple sclerosis (SPMS), whereby they experience a progressive neurological deterioration. They may still suffer from superimposed relapses. A subcategory of RRMS patients (around 20%) has benign MS. These patients have rare and mild relapses and a long course of disease with minimal or no disability. If patients have a steady neurological decline from the onset, without relapses, they are described as having primary-progressive multiple sclerosis (PPMS). This comprises approximately 15–20% of people with the disease

A fourth, rare type of MS is progressive-relapsing multiple sclerosis (PRMS), which is considered a variant of PPMS with similar prognosis. In patients with PRMS, there is a gradual neurological decline from the beginning. It is similar to PPMS, but has superimposed, acute relapses.

Demographics

According to the National Multiple Sclerosis Society, approximately 400,000 Americans acknowledge having MS, and every week about 200 people are diagnosed. Worldwide, MS may affect 2.5 million individuals. The usual age of onset is within the third and fourth decades, although the disease can begin in childhood and also above the age of 60 years. Overall, MS occurs more frequently in women than in men, and the female-to-male ratio is approximately of 2:1. This female predominance is less defined in patients with PPMS, which typically develops at a later age.

There is a variation in the worldwide distribution of MS, with the highest prevalence in the northern and central Europe, northern North America and southeastern

Australia. Clusters, or areas with more than the expected amount, occur. There are also racial differences, with a low prevalence in Asians and Africans or people of African descent, and a higher frequency in Caucasians, especially of northern European descendent. MS is rare between the equator and latitudes 30°–35° north and south. The prevalence of MS increases proportionally with increased distance from the equator. There is no satisfactory explanation of this phenomenon, although certain variables have been researched. These include environmental factors, such as climate, humidity, hours of daily sunshine, resistance to certain viruses, and even consumption of cow's milk.