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Unclear Signals:
Understanding Multiple Sclerosis is First Step Towards a Cure
You pick up the telephone to call your best friend. You dial a number which will, in effect, let the phone know where to send the signals. But unbeknownst to you, something has worn away the rubber which covers and protects the wires within your phone. Some signals cannot get through, and the ones that do are ambiguous. As a result your important information does not get conveyed to your friend.
This is a circumstance similar to the process that occurs within the body of a person with Multiple Sclerosis, a disease of the spinal cord and brain which affects over 300,000 Americans. The onset of Multiple Sclerosis, or MS, usually occurs between the ages of 22 to 33 years of age and most frequently affects women between the ages of 30 and 50.(1) Yet Multiple Sclerosis is one of the few neurological diseases which is characterized by remission (the disappearance of symptoms for an extended period of time.) As a result, it is likely that scientists will be able to discover therapies for the disease because if they are able to figure out how and why the remission of Multiple Sclerosis occurs, they might be able to force the body into a state of constant remission.
Transmitting Signals: A Look at the Nervous System
Before taking a closer look at Multiple Sclerosis, it is important to understand the body's nervous system, which is composed of the central and peripheral nervous systems. The central nervous system, which is made of the brain and the spinal cord, is responsible for the integration of information. The peripheral nervous system, which is constituted by all additional nerve cells not in the central nervous system, is responsible for conveying information to and away from the central nervous system to various parts of the body.
Neurons, or the units of nerve cells, have extremely complex structures to assure maximum efficiency in transmitting information. Each neuron has a large cell body which contains the nucleus of the cell as well as other cellular organelles which help with maintenance functions of the cell. Dendrites, or fiber-like extensions which increase the surface area of the cell to increase effectiveness, receive information from other cells. Axons are larger extensions of the cell which transmit information away from the cell body towards other cells.
Each axon is enclosed by a chain of cells called Schwann cells which support the neuron. While these cells do not function in transmitting sensory information, they support the cells structurally and by controlling the passage of substances into the cells. Together these cells form an insulating layer around the neurons called the myelin sheath.
This myelin sheath is similar to the rubber which coats the wires of your telephone. Yet in a person with Multiple Sclerosis, the immune system mistakenly identifies some component of myelin as a foreign agent, or antigen. This elicits an auto-immune response in which the body attacks and slowly destroys this protective covering and replaces it with hard scar tissue. It also forms a series of lesions on different areas of the brain. The result is a temporary interruption of nerve transmission, or disordered transmission that is similar to what might occur if the wires in your telephone were stripped of their protection. The brain ceases to send the correct information to the rest of the body. The reason the immune system of an MS patient identifies its own myelin as foreign and attacks it is one of the many still unknown issues surrounding the disease.
The Result of Unclear Signals: Symptoms of MS
The jumbled set of nerve transmissions, like the telephone message which cannot get through as a result of the damaged protective covering, most frequently occurs in neural pathways connected with vision, sensation, and the use of limbs. It can occur, however, in all neural pathways. As a result, there is a wide range of symptoms for the disease, and these often vary from person to person. The intensity of symptoms and length that they last also varies greatly dependent upon which areas of the central nervous system have been affected and to what extent. This is analogous to the possible variations of your phone conversation with your friend which might occur depending on which wires were left unprotected.
In a person with Multiple Sclerosis, the signals sent by the brain arrive at the target site as ambiguous messages, just as the message you needed to tell your friend would not arrive clearly if the telephone wires lost their rubber coating. Among the most common symptoms as a result of such unclear signals are weakness and muscle spasticity, or muscle stiffness, which often affects walking and mobility. This is often accompanied by coordination and balance problems including loss of balance, tremors, ataxia (unstable walking), and limited use of limbs. MS patients also often encounter problems related to sensation including tingling (constant pins and needles feeling), paraesthesia (numbness), and lack of sensitivity or extreme sensitivity to heat. A large number of people with MS experience fatigue which is often debilitating and out of proportion with the amount of physical exertion they have done.
Some people with Multiple Sclerosis have difficulties in other areas as well. Many people have visual problems which may include blurred vision, double vision, optic neuritis, and involuntary rapid eye movement. Others have speech impediments and may slur words or speak at a slowed rate. Others still have difficulties with bladder control or sexuality which may include impotence or loss of sensation. A few people with MS experience cognitive problems as well, including lack of short term memory or concentration. Each of these symptoms occur because the signals the body sends out arrive as jumbled messages since they are not protected during transmission.
Many Mixed Signals: Types of MS
Just as the symptoms of Multiple Sclerosis are varied, so too are the forms of the disease. Symptoms of MS are often not present at all times and the disease is characterized by a serious of exacerbations, or "attacks," in which old symptoms recur and are often accompanied by the onset of new symptoms. Depending on severity and frequency of exacerbations, a person may have one of four forms of Multiple Sclerosis: benign, relapsing-remitting, secondary progressive, or primary progressive.
Benign MS is the least severe form of the disease. Approximately 20% of people with Multiple Sclerosis have this form of the disease.(2) A person with benign MS will often experience symptoms relating to optic nerves, and these symptoms will be less severe at the onset of the disease than in people with other forms of MS. Benign MS is also characterized by complete recovery after initial attacks, and a low frequency of reoccurrence of these exacerbations. In addition, a person with benign MS will not experience worsening of symptoms or frequency of attacks with time, and will have no permanent disability. Benign MS is similar to what might occur if one minor telephone wire lost its rubber coating; a few transmissions are jumbled, but not to the extent where total communication is impossible.
Relapsing-remitting MS occurs within 25% of Multiple Sclerosis patients.(3) A person with relapsing-remitting MS will experience attacks at unpredictable times. These exacerbations will be accompanied by new symptoms and/or an increase in severity of old symptoms. The frequency of attacks may or may not increase with time, but there will be remission (either partial or total) between attacks. This is like white might happen if the coating on several telephone wires was cut away and then partially repaired and then cut away again at random time intervals.
Secondary progressive MS is characterized by the development of a progressive disability. Approximately 40% of people with Multiple Sclerosis have this form of the disease.(4) A person with secondary progressive MS will experience relapses and frequent attacks, and is likely to experience more symptoms than a person with either benign or relapsing-remitting MS. Secondary progressive MS might be compared to the previous analogy of cutting away the rubber coating on the telephone wires at unpredictable time, but would probable involve the loss of a greater amount of the protective covering than for relapsing-remitting MS.
Primary progressive MS is the most severe form the disease takes. Only about 15% of people with Multiple Sclerosis are diagnosed with this type of the disease.(5) A person with primary progressive MS will not experience exacerbations which are distinct from one another. Instead such a person will have a slow onset of symptoms which will grow steadily worse. Like someone who has secondary progressive MS, a person with secondary progressive MS will often experience a wide range of symptoms. Primary progressive MS is similar to what might occur if slowly and steadily the rubber coating on the wires of your telephone were eaten away.
***Note: This is not a self-diagnostic test. If you think you or a family member might have Multiple Sclerosis, consult your doctor.***
Which Wires: A Look at Contributing Factors to MS
It is unclear as to why people develop different forms of Multiple Sclerosis, partially because it is still unclear as to exactly how people acquire the disease. It is also unknown as to why women and other specific communities, such as Caucasian populations,(6) are more likely to develop the disease. Multiple Sclerosis is not contagious, nor is it directly inherited. There are, however, some genetic links to the disease. Little is known about the exact genetic contribution, but since there is a markedly increased rate of Multiple Sclerosis in children of people with the disease, there is clearly some involvement of genetics in the disease.(7)
Currently there is a substantial amount of research being conducted to discover the precise contribution of genetics to acquiring Multiple Sclerosis. It is probable that MS is affected by the activity of several different genes. There is an area on chromosome six which contains a concentration of genes which are involved in actions relating to the immune system. Because Multiple Sclerosis is an attack on the myelin by the immune system, a deficiency or deformity in this area is likely to have some role in the acquisition of MS. To what extent these genes, and other gene areas on chromosomes 5, 7, 17, and 19 contribute to Multiple Sclerosis is still a point of contention for researchers.(8)
Yet, like many other diseases, genetic contribution is not the sole factor which determines whether or not a person will acquire Multiple Sclerosis. It is possible that in different populations or environments, different genes influence the onset of Multiple Sclerosis. This might help to explain some demographic information related to MS, including the fact that the closer a population is to the equator, the fewer cases of Multiple Sclerosis that can be found.(9)
Setting the Signals Straight: Drug Therapy Options
In addition to searching for the cause of Multiple Sclerosis, researchers are currently looking for drug therapy methods to halt the progression of the disease, to set the signals straight. As of yet no cure has been found, but in recent years there has been an upsurge in the drug treatments available to MS patients. Among the most exciting new drug therapy often prescribed to people with Multiple Sclerosis are drugs with the commercial names Betaseron, Avonex, Copaxone, Zanaflex, ACTH, and Corticosteroids. Each is taken for different symptoms that accompany MS and many are targeted only at one of the four forms of the disease. As a result of this, in addition to the exorbitant prices of many of these drugs, it is still difficult for a large number of MS patients to receive treatments that effectively combat the individualized form the disease has taken.
For a brief summary on the workings of these drugs, common side effects, and other relevant information, click below:
Permanent Repairs:Looking for a Cure
Though all of these drugs and hormones may be given to people with Multiple Sclerosis to halt the progression of the disease or to combat specific symptoms, as of yet there is no cure for MS. In addition, there is still no way of knowing the course the disease will take for any given individual. A person with MS can not know at what rate disability or symptoms will worsen, nor can such a person know the time span between exacerbations.
There is, however, hope that in the near future better treatment, and possibly even a cure for Multiple Sclerosis may be found. Research teams around the world, headed by groups in Canada, Israel, and the United States, are always searching for improved ways of understanding the mechanisms of Multiple Sclerosis. Perhaps when scientists are able to answer what is as of yet unknown about the disease they will be able to start working on methods to permanently cure the disease.
Some research groups are studying myelin basic protein, one of the major components of myelin which is thought to be a possible target of auto-immune attacks on myelin in people with Multiple Sclerosis. It is still unclear as to the exact function of myelin basic protein or how it is produced. Perhaps if this information is discovered and researchers are able to find a difference in the myelin basic protein of people with MS that might illicit such an auto-immune response, they will be able to find ways in which the myelin basic protein in people with MS can be altered or restructured so that the immune system no longer tags them as foreign agents and attacks them.(10)
Other promising research is related to current studies about the body's natural means of repairing myelin. There is evidence that the body repairs damage to the myelin sheath, especially during the early stages of Multiple Sclerosis. Studies into the workings of oligodendroyctes, the cells which produce myelin, should shed light on how myelin in assembled in the body, and will hopefully lead to a way of artificially manufacturing myelin or stimulating the body to repair its own damaged myelin.(11)
It is unlikely, however, that a total cure for Multiple Sclerosis will be found within the next year or so. There is still too much about the disease that is unknown. Questions ranging from how myelin is manufactured in the body to why Multiple Sclerosis takes such varied courses in different people are still unanswered. Yet people with Multiple Sclerosis continually have new drug treatments available to them that can help halt the progression of the disease, and many have hope that it will not be too long before a total cure for the disease is found.
