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What is Multiple Sclerosis?

 

"Ok then, what is Multiple Sclerosis?"

Multiple Sclerosis (MS) is an inflammatory disease of the Central Nervous System (CNS) - that's the brain and spinal cord. Predominantly, it is a disease of the "white matter" tissue. The white matter is made up of nerve fibres which are responsible for transmitting communication signals both internally within the CNS and between the CNS and the nerves supplying rest of the body.

In people affected by MS, patches of damage called plaques or lesions appear in seemingly random areas of the CNS white matter. At the site of a lesion, a nerve insulating material, called myelin, is lost. I shall explain this process in more detail later. Clinically, MS is a hard condition to characterise because it is very unpredictable and variable. Depending on which areas of the CNS are affected and how badly they are damaged, the type and severity of symptoms can vary greatly.

No two people get MS in exactly the same way and the expression of each individual's disease is as unique as their fingerprints. However, the different courses of the disease, both within an individual and within the whole population, principally differ in their timing, location and severity. Underneath similar processes (including demyelination and sometimes other forms of nerve degeneration) are going on.

Although recent research indicates that the biochemical make-up of lesions may vary between different forms of the disease, this is not the reason why people with MS (PwMS) have such widely differing symptoms - it's because nerve damage to one site usually causes completely different symptoms than damage to another.

In general, people with MS can experience partial or complete loss of any function that is controlled by, or passes through, the brain or spinal cord.

"That's sounds terrible - doesn't almost everything go through the brain?"

Well yes, MS can be and often is a very serious disease but almost nobody loses function in all possible areas and some people are affected much worse than others. People with MS can experience any of the following problems either fully or partially - numbness, tingling, pins and needles, muscle weakness, muscle spasms, spasticity, cramps, pain, blindness, blurred or double vision, incontinence, urinary urgency or hesitancy, constipation, slurred speech, loss of sexual function, loss of balance, nausea, disabling fatigue, depression, short term memory problems, other forms of cognitive dysfunction, inability to swallow, inability to control breathing ... you name it.

"Crikey, it sounds devastating"

Yes, but don't forget that it is usually a slowly progressing disease and few people, if any, experience all the possible symptoms. Three quarters of people with MS don't need to use a wheelchair and those that do find that it gives them greater freedom to do the things they want. Many people will require a cane after a number of years of disease activity. Other people will have only very mild and occasional symptoms. Still others have been found to have had MS as a result of an autopsy even though they never presented with any clinical symptoms during their lives. A minority of people with MS die as an indirect result of the disease in its later stages. The majority of PwMS will lie somewhere between these extremes. Adjustments have to be made, but most people with MS can live fulfilled and active lives.

"Can you catch MS from someone with it?"

Absolutely not. Studies have been done on children adopted into families where one of the parents has MS and they have been found to have the same incidence of the disease as the background population [Sadovnick, Ebers et al, 1999]. Other studies show that the number of husband-wife copresentations is almost exactly what you would expect for a non-contagious disease [Ebers, Sadovnick et al, 2000]. This is worth emphasising - you cannot catch MS from a person with the disease. Multiple sclerosis is not contagious nor infectious.

"Are their different types of MS?"

Yes, there are four main varieties as defined in an international survey of neurologists [Lubin and Reingold, 1996]. (All the graphs show level of disability over time - where two lines appear in the graph it denotes two possible courses of that form of MS.)

1. Relapsing/Remitting (RRMS):

This is characterised by relapses (also known as exacerbations) during which time new symptoms can appear and old ones resurface or worsen. The relapses are followed by periods of remission, during which time the person fully or partially recovers from the deficits acquired during the relapse. Relapses can last for days, weeks or months and recovery can be slow and gradual or almost instantaneous. The vast majority of people presenting with Multiple Sclerosis are first diagnosed with relapsing/remitting. This is typically when they are in their twenties or thirties, though diagnoses much earlier or later are known. Around twice as many women as men present with this variety.

2. Secondary Progressive (SPMS):

After a number of years many people who have had relapsing/remitting MS will pass into a secondary progressive phase of the disease. This is characterised by a gradual worsening of the disease between relapses. In the early phases of Secondary Progressive, the person may still experience a few relapses but after a while these merge into a general progression. People with secondary progressive may experience good and bad days or weeks, but, apart from some remission following relapsing episodes, no real recovery. After 10 years, 50% of people with relapsing/remitting MS will have developed secondary progressive [Weinshenker et al, 1989, Runmarker and Andersen, 1993, Minderhoud et al, 1988]. By 25 to 30 years, that figure will have risen to 90% [Ref].

3. Progressive Relapsing Multiple Sclerosis (PRMS):

This form of MS follows a progressive course from onset, punctuated by relapses. There is significant recovery immediately following a relapse but between relapses there is a gradual worsening of symptoms.

4. Primary Progressive (PPMS):

This type of MS is characterised by a gradual progression of the disease from its onset with no remissions at all. There may be periods of a leveling off of disease activity and, as with secondary progressive, there may be good and bad days or weeks. PPMS differs from Relapsing/Remitting and Secondary Progressive in that onset is typically in the late thirties or early forties, men are as likely women to develop it and initial disease activity is in the spinal cord and not in the brain. Primary Progressive MS often migrates into the brain, but is less likely to damage brain areas than relapsing/remitting or secondary progressive - for example, people with Primary Progressive are less likely to develop cognitive problems.

Other terms often used to describe forms of multiple sclerosis are:

Benign MS: This is a sub-group of relapsing/remitting. It is used to describe the disease in people who have had MS for fifteen or more years without picking up any serious and enduring disability. One of the neurologists that I saw put it at ten years. It's a bit of a false label really and people with benign MS are often reclassified as Secondary Progressive after a number of years [Hawkins and McDonnell, 1999].

Malignant MS: Also known as Marburg's Variant and Acute Multiple Sclerosis. This is a label given to forms of MS where the disease progresses very rapidly from onset leading to severe disability within a relatively short period of time. Fortunately, this form of MS is extremely rare.

Chronic Progressive MS: Primary Progressive and Secondary Progressive used to be lumped together as Chronic Progressive (CPMS) but this term is no longer officially recognised although you will still see it referred to now and then.

Transitional/Progressive MS: Another form of the disease which is sometimes referred to but not widely used, is Transitional/Progressive (TPMS). This is characterised by a progressive course beginning many years after an isolated bout.

Devic's Disease: Also known as Neuromyelitis Optica, Devic's disease is a related condition to multiple sclerosis that is characterised by an attack of Optic Neuritis in both eyes followed by severe inflammation of the spinal cord (Transverse Myelopathy).

Balo's concentric sclerosis: This is another very rare disease that resembles multiple sclerosis. Clinically, it is very hard to distinguish Balo's concentric sclerosis from MS but MRI scans show the lesions in Balo's to be concentric rings of intact myelin and demyelinated zones. It is more common in China and the Philippines than elsewhere.

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