Multiple Sclerosis


The name itself is revealing: multiple, more than one, and sclerosis, which refers to areas of sclerotic (scarred) tissue. Multiple sclerosis is a demyelinating disease of the white matter of the central nervous system.

These areas of sclerosis, also referred to as lesions or plaques, occur in the white matter of the central nervous system. Gray matter consists primarily of nerve cells. Axons (nerve fibers) are the connections between the cell body and the muscles, sensory organs, and primary organs such as the heart. These nerve cells are the communication system both within the central nervous system and between it and the rest of the body. Axons are sheathed in myelin, a white substance (hence the term "white matter") that insulates them and speeds transmission of impulses along the cell fibers. Electrical impulses move along the nerve fiber to the synapse (the connection point between cells) to the next nerve cell.

The lesions or plaques of multiple sclerosis are areas of tissue damage arising from inflammation, which occurs when white blood cells and fluid accumulate around blood vessels. This inflammation causes destruction of myelin. After the fragments are cleared away, a scar is formed--the lesion--in the area of demyelinization. The cause-and-effect process of inflammation and demyelinization is unclear. These lesions impede conduction of signals by blocking or slowing communication, either completely or partially and from time to time. The process can be thought of as similar to an electrical short circuit. The symptoms of multiple sclerosis result from that loss or diminution of signal conduction.

MS is the most common demyelinating disease of the central nervous system. In the United States alone, there are at least 250,000 cases. For reasons that remain unclear, it is more prevalent in northern temperate zones and affects noticeably more women than men. The average age of onset is thirty years.

Research into the underlying causes and processes of MS is ongoing, and in recent years, advances in virology and immunology have rapidly increased knowledge and understanding of the disease. However, its etiology remains unclear. Epidemiological studies indicate that an environmental factor, perhaps exposure to a virus, when combined with a genetic predisposition to the disease, may well control occurrence of the disease. MS is not a genetically transmitted disease. MS may also be or involve a defect of some kind in the body's autoimmune system--some part of the body may, in effect, attack itself.

Diagnosis of MS is difficult. A medical history and clinical examination must show at least two separate lesions that have occurred at more than one time. Obviously, any other possible causes must be ruled out. Because of the difficulty of diagnosis, the presence of MS is usually deemed to be either definite, probable, or possible. There is no one specific diagnostic test that can either confirm or rule out its presence. A neurological examination can indicate lesions through the presence or absence of various signs and reflexes. A sign is an abnormality detected through examination, while a symptom is a subjective complaint noted by the patient. There is not necessarily a correlation between symptoms and signs. Signs may confirm symptoms or they may be asymptomatic. Symptoms may exist in the absence of signs. Computerized tomographic (CT) scans will show some lesions. Magnetic resonance imaging usually reveals many more lesions than the CT scan, including some that may be subclinical, that is, they are not detectable through examination and may have no associated symptoms. An autopsy will usually show many more lesions than were ever suggested by either symptoms or signs. These lesions are probably the result of subclinical attacks of the disease. Computerized testing of evoked potentials tests the brain's electrical responses to various forms of stimulation of the eyes, ears, or other parts of the body. Delays in these responses may indicate lesions that are clinically silent (producing no symptoms) and can sometimes firm up a questionable diagnosis from probable to definite MS. Testing of the cerebrospinal fluid for protein content, the number and type of white blood cells, and the amount of Ig6, a gamma globulin, can also support a diagnosis.

Symptoms of MS vary enormously, both from patient to patient and, over time, in one patient. Symptoms may include tingling, pins and needles, numbness, double or blurred vision, clumsiness of fine movements or of walking, frequency and urgency of urination, muscle weakness and spasms, pain or paralysis, incoordination, and mood or