MS is the abbreviation for multiple sclerosis. The MS definition alone does not answer the question – what is MS? Answers to some related questions with a focus on certain aspects of the disease are the best answer.
MS is an autoimmune demyelinating disease of the central nervous system. It mainly involves the white matter of the brain and/or spinal cord. By definition, there must be dissemination of lesions in space and time. This means there must be objective evidence of two or more demyelinating lesions occurring on two or more occasions in time. Evidence of the lesions can be in the form of physical signs, symptoms, or brain MRI scan findings. The lesions must be in two or more areas of the brain or spinal cord that the disease typically affects.
Multiple sclerosis prevalence
The prevalence of MS varies by geography. The rate of occurrence among a population is proportional to how far it is to the north or south of the equator. Hence, MS is more common in colder climates.
Approximately four hundred thousand people in the U.S. population have the disease. This is a rate of roughly ninety out of a hundred thousand. It afflicts approximately 2.5 million people worldwide.
MS symptoms can begin anywhere between the ages of 10 and 80. But they most commonly began between 20 and 40 years of age. The average age at which symptoms begin is 32.
Multiple sclerosis pathophysiology and pathology
A succinct discussion of the pathophysiology (what goes wrong in the body) of MS is an integral part of the answer to the question – what is MS? The earliest pathology is recurrent bouts of inflammation. That inflammation leads to damage and destruction of myelin that covers the axons of nerves. Involvement is not limited to myelin in white matter though. According to research, it also can involve the small amounts of myelin in the gray matter of the cortex of the brain. The myelin in that area covers the axons that connect brain cells in that region. Varying degrees of damage also occurs to the axons themselves as well as the nerve cell bodies and dendrites that form the gray matter of the cortex of the brain. The latter explains the loss of brain volume in some patients, even in the early stages of the disease.
The classic structural lesion of MS in its latter stages is the presence of scattered plaques in various parts of the brain and spinal cord. The name, multiple sclerosis is based on the fact that these plaques which contain scar tissue are visible in multiple areas on inspection of the brain with the naked eye. Based on findings within early and late plaques, the disease seems to start with T lymphocytes and macrophages attacking the myelin. They presumably recruit and direct other types of immune cells that also participate. The end result is inflammation, damage and destruction. The actual trigger of the attack is unknown though.
The signs and symptoms of MS in a given person depend on the number of nerves involved; the severity of the pathology; the part of the brain or spinal cord affected; and the degree to which glial cells can mount a response to repair damage caused by the attack. Proof of this theory is not absolute, but the interrelationship between these opposing processes probably accounts for the different types of MS based on the course the disease follows.
What causes MS?
The answer to the question – what causes MS – is speculative. But it involves an answer to the related question – is MS genetic? First of all, a number of theories exist as to what triggers immune cells to attack myelin. The different theories mention sundry environmental factors thought to be involved. They all lack proof though. A popularly held theory is that a virus triggers the attack. Some think it is one particular virus. Others think it might be any one of several viruses.
The cause of MS is not genetic in terms of being an inherited disorder passed on by one or both parents. Based on research though, one’s genetic makeup does appear to affect susceptibility to it. Research studies of two variant genes seem to bear out this notion. Also, observations have shown an increased risk among first, second, or third-degree relatives. The risk is highest in the identical twin of a person with the disease. The incidence is not as high, but is still higher in other first-degree relatives of a person who has the disease.
In light of the regional differences in the prevalence of MS and the genetic data from research and observations, most experts are of the belief that environmental and genetic factors are both involved. They deem environmental factors as the trigger and genetic factors as determinants of susceptibility.
Types of MS
There are 4 main types of MS based on the course the disease follows. They are the following:
- relapsing-remitting multiple sclerosis
- secondary-progressive multiple sclerosis
- primary[progressive multiple sclerosis
- progressive-relapsing multiple sclerosis
Relapsing-remitting Multiple Sclerosis (RRMS)
RRMS is the most common type of MS. Between 80% and 85% of people have this form when first diagnosed. Its course fluctuates. Patients with it experience new symptoms or worsening of existing symptoms at unpredictable times. Names for these episodes of worsening are attacks, exacerbations or relapses. They may last from days to months. Total or partial recovery eventually follows the attacks. Remission (recovery) might last for months to years, during which time the person might appear to be free of disease.
Secondary-Progressive Multiple Sclerosis (SPMS)
SPMS is a form of MS in which patients start out having relapses and remissions. At some point though, some of their symptoms start to steadily worsen. Relapses and remissions of other symptoms might continue. But the net disease course is progression of disability. Most patients with RRMS eventually convert to this type.
Primary-Progressive Multiple Sclerosis (PPMS)
PPMS is a form of the disease in which there is progression of symptoms from the outset. There are no actual relapses or remissions. But the rate of progression of symptoms might vary over time. There might also be occasional plateaus or minor improvements. This type accounts for approximately 10% of the cases.
Progressive-Relapsing Multiple Sclerosis (PRMS)
PRMS is the least common form of the disease. Its course is one of progression from the outset. Occasional exacerbations occur along the way; but there is no true recovery; and progression is the rule.
What-is-MS summarizing highlights
MS is a chronic inflammatory disease of the brain and spinal cord. It attacks myelin but can also cause damage to the axons and other parts of the nerve cells. Its cause is unknown; but environmental and genetic factors appear to be involved. There are four main courses that it can follow. It is not acutely life threatening. But it does lead to long-term disability.
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