Multiple Sclerosis (abbreviated MS, also known as disseminated sclerosis orencephalomyelitis disseminata) is a chronic inflammotory demyelinating disease. that affects the central nervous system(CNS).
Multiple sclerosis (MS) is a nervous system disease that affects your brain and spinal cord. It damages the myelin sheath, the material that surrounds and protects your nerve cells.
Multiple sclerosis attacks neurons, the cells of the brain and spinal cord that carry information, create thought and perception, and allow the brain to control the body. Surrounding and protecting these neurons is a layer of fat, called myelin, which helps neurons carry electrical signals. MS causes gradual destruction of myelin (demyelination) in patches throughout the brain and/or spinal cord. Myelin not only protects nerve fibers, but makes their job possible. When myelin or the nerve fiber is destroyed or damaged, the ability of the nerves to conduct electrical impulses to and from the brain is disrupted, and this produces the various symptoms of MS.
The name multiple sclerosis refers to the multiple scars (or scleroses) on the myelin sheaths. MS results from attacks by an individual’s immune system on his or her own nervous system, and it is therefore categorized as an autoimmune disease.
Multiple sclerosis can take several different forms, with new symptoms occurring in discrete attacks or slowly accruing over time. Between attacks symptoms may resolve completely, but permanent neurologic problems often persist. Although much is known about how MS causes damage, the exact cause of MS remains unknown. MS primarily affects adults, with an age of onset typically between 20 and 40 years, and is more common in women than in men.
Symptoms of Multiple Sclerosis
Individuals with multiple sclerosis may experience a wide variety of symptoms. The initial attacks are often transient, mild (or asymptomatic), and self-limited. They often do not prompt a health care visit and sometimes are only identified in retrospect once the diagnosis has been made based on further attacks. The most common initial symptoms reported are: changes in sensation in the arms, legs or face (33%), complete or partial vision loss (optic neuritis) (16%), weakness (13%), double vision (7%), unsteadiness when walking (5%), and balance problems (3%). Fifteen percent of individuals have multiple symptoms when they first seek medical attention. Most people find their initial MS symptoms occur over a period of hours to weeks. For some people the initial MS attack is preceded by infection, trauma or strenuous physical effort.
Other symptoms and physical findings common in MS are flickering eye movements (nystagmus), speech difficulties, tremor, clumsiness of the hands, abnormal muscle spasms, bladder and bowel difficulties, and sexual dysfunction. Cognitive impairments are also common, such as difficulty performing multiple tasks at once, difficulty following detailed instructions, loss of short term memory, emotional instability, and fatigue. Emotional symptoms are common and can be the normal response to having a debilitating disease or the result of damage to the nerves that generate and control emotions. The most common condition, clinical depression, is a product of both causes. Feelings such as anger, anxiety, frustration, and hopelessness are also common, and suicide is a very real threat.
This damage slows down or blocks messages between the brain and body, leading to the symptoms of MS. MS can cause a variety of symptoms including-
- Changes in sensation (in arms, legs or face). Sensations such as numbness, prickling, or “pins and needles”
- Visual problems (complete or partial vision loss and double vision)—optic neuritis, nystagmus or diplopia.
- Muscle weakness.
- Depression,thinking and memory disturbances.
- Difficulties with coordination and speech.
- Severe fatigue.
- Cognitive impairment.
- Problems with balance (ataxia).
- Overheating, and pain.
- Bladder and bowel difficulties.
- Impaired mobility and disability in more severe cases.
The initial attacks are often transient , mild(asymptomatic) and self limited. The atacks are generally preceeded by infection, trauma or sternous physical activities.
Multiple sclerosis affects neurons, the cells of the brain and spinal cord that carry information, create thought and perception, and allow the brain to control the body. Surrounding and protecting some of these neurons is a fatty layer known as the myelin sheath, which helps neurons carry electrical signals. MS causes gradual destruction of myelin sheath (demyelination) and transection of neuron axons in patches throughout the brain and spinal cord. The name multiple sclerosis refers to the multiple scars (or scleroses) on the myelin sheaths. This scarring causes symptoms which vary widely depending upon which signals are interrupted.
The predominant theory today is that MS results from attacks by an individual’simmune system on the nervous system and it is therefore usually categorized as anautoimmune disease. There is a minority view that MS is not an autoimmune disease, but rather a metabolically dependent neurodegenerative disease. Although much is known about how MS causes damage, its exact cause remains unknown.
Causes of Multiple Sclerosis
Although many risk factors have been identified but no definite cause has been found. MS most likely occurs as a result of combination of both environmental and genetic factors.Some accept autoimmune expalnations too.
The most popular hypothesis is that a viral infection or retroviral reactivation primes a susceptible immune system for an abnormal reaction later in life.
Since it seems to be more common in people who live farther from the equator, another theory proposes that decreased sunlight exposure and so decreased Vit – D production may help causing it.
An imbalance between Th1 type of helper T- cells which fight infection , and the Th2 type,which are more active in allergy and more likely to atack the body provides other explanation.
Other theories describe MS as an immune response to a chronic infection.The association of MS with the Epstein-Barr virus suggests a potential viral contribution.Chlamydophila and Spirochetal bacterias are often found in association.
Severe stress may be a contributing factor.
Smoking has been shown to be an independent risk factor for developing MS.
MS is not considered a hereditary disease . But scientiic evidence suggests that genetics play a determining role in a person’s susceptibility to MS. In a population at large , the chance of developing MS is less then a tenth of one percent. However if one person in the family has MS , that person,s first degree relatives – parents , children and siblings – have a one to three percent chance of developing it.
Studies of families with multiple cases of MS and research comparing proteins expressed in humans with MS to those of mice suggests that an area related to MS susceptibility may be located on Chromosome 5. Other regions on chromosomes 2 , 3 , 7 , 11, 17 , 19, and X have been identified as possibly containing genes involved in the development of MS.
These studies strengthen the theory that MS is the result of a number of factors rather then a single gene or other agent. Development of MS is likely to be influenced by the interactions of a number of genes, each of which (individually) has a modest effect. Additional studies are needed to specifically pin point which genes are involved.
Disease sub-types of Multiple Sclerosis
The course is difficult to predict and the disease may at times either lie dormant or progress steadily. Several sub types , or, paterns of progression have been described.
Sub-types use the past course of the disease in an attempt to predict the future course.
Following four sub types are identified:
1) Relapsing – remitting
It describes the initial course of 85 – 90 % of individuals with MS. It is characterised by unpredictable attacks (relapses ) followed by periods of months to years of relative quiet (remission )with no new signs of disease activity. Deficits suffered during may either resolve or may be permanent . When deficits always resolve between attacks , this is referred to as benign .
2) Secondary progressive
Secondary progressive describes around 80% of those with initial relapsing – remitting MS,who then begin to have neurologic decline between their acute attacks without any definite periods of remission. This decline may include new neurologic symptoms , worsening cognitive function, or other deficits. Secondary progressive is the most common type of MS and causes the greatest amount of disability.
3) Primary progressive
It describes the approximately 10 % of individuals who never have remission after their initial MS symptoms . Decline occurs continously without clear attacks. The primary progressive sub type tends to affect people who are older at disease onset.
4) Progressive relapsing
It describes those individuals who , from the onset of their MS have a steady neurologic decline but also suffer superimposed attacks and is one of the less common types.
Factors triggering a relapse
Multiple sclerosis relapses are often unpredictable and can occur without warning with no obvious precipitating factors. Some attacks are however preeceded by common triggers. In general , relapses occur more frequently during spring and summer than during autumn and winter.Infections such as common cold , influenza and gastroenteritis increase the risk of the relapse.
Emoitional and physical stress may also trigger an atack. Stastistically there is no good evidence that either trauma or surgery trigger the relapses.People with MS can participate in sports but they should avoid extremely sternous exertion as heat can increase symptoms..This is known as Uhthoff’s phenomena.This is why some people avoid saunas or even hot showers if suffering from MS.
Pregnancy can directly affect the susceptibility for relapse. The last three months of pregnancy offer a natural protection against relapses. However during the first few months after delivery ,the risk for a relapse is increased 20 % – 40 % .Pregnancy does not seem to influence long term disability . Children born to mothers with MS are not at increased risk for birth defects or other problems.