About Multiple Sclerosis
Thanks to the Multiple Sclerosis Society of New Zealand for this content. For further and more in-depth information please go to their website www.msnz.org.nz
MS is a disorder of the central nervous system (CNS) which includes the brain, spinal cord and optic nerves.
The CNS is responsible for our conscious and unconscious functioning, including movement and the response to sensations such as sight, touch and hearing. It directs these functions by sending its instructions in the form of electrical impulses to the appropriate sites along nerve fibres. Nerve fibres are coated in a protective insulating covering called the myelin sheath—this serves a very similar function to the coating around electrical wires. Myelin is important in speeding electrical conduction along nerve fibres and in insulating nerve fibres from one another. |
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The term multiple sclerosis refers to multiple areas of scarring (sclerosis) scattered throughout the brain and spinal cord. These scars are the result of healing patches of inflammation that are the basic cause of damage to nerve fibres and of the suddenly appearing symptoms that are referred to as an attack, exacerbation or relapse.
Patches of inflammation heal spontaneously over several weeks or months when symptoms may resolve completely or residual impairment may result, if they do not.
The inflammation causes damage particularly to the insulating myelin sheath covering nerve fibres, but may also damage the nerve fibres (axons) themselves.
In MS, the typical damage is often referred to as “demyelination”. The nature of the symptoms and their severity depends partly on the site of the patch of inflammation (or lesion) and partly on its nature and intensity.
The course of MS varies widely from person to person. Some people will only ever experience mild symptoms over their lifetime while others will have relapses followed by incomplete remission when disability may worsen in a stepwise fashion with each relapse experienced. A number of people experience slowly progressive, worsening of disability over many months or years. There is uncertainty how much of this progressive process is due to low-grade inflammation and how much to loss of previously damaged nerve fibres.
What are the symptoms of MS?
In MS the condition and symptoms are unpredictable and vary from person to person. Symptoms are not only different in different people, but typically vary in the same person from time to time as different areas of the central nervous system become inflamed and scarred.
Common symptoms include:
- Lack of coordination or weakness in the limbs;
- Impaired balance or instability walking;
- Sensory disturbances;
- Blurred or double vision;
- Impaired urinary or sexual function;
- Cognitive dysfunction such as impaired memory or concentration;
- Fatigue.
A person with MS will usually experience more than one symptom but NOT necessarily all of them.
What Causes MS?
The cause of MS is still not known.
Both genetic and environmental factors are important, but how they interact to produce episodes of localised inflammation over many years is not clear.
MS is widely regarded as an autoimmune disease. Here the body produces a misdirected immune system attack on its own tissue—in this case the myelin sheath that protects the axons, but that has never been firmly established.
A reaction to a virus hidden in the CNS has been long suspected, but also not proven. In persons with MS, the immune system appears to be normal in all other respects.
MS is not a hereditary disorder in the sense of being passed directly from parent to child. The increased risk in close family members is not attributable to a single gene, but most likely related to several genes whose function is not well understood—some of these probably influence the body’s immune reactions.
A striking environmental feature is the increase in prevalence of MS in higher latitudes both above and below the equator.
In NZ, for example, the prevalence in the South Island is approximately twice that in the upper half of the North Island. The pattern of migration from Northern Europe may contribute to that distribution, but undetermined environmental factors are most important.
Among many possibilities, exposure early in life to a virus infection that has a long-term effect on immune responses is thought most likely. However, none of the numerous viruses suspected can be directly linked at present.
Diagnosis & Types of MS
How is MS Diagnosed?
Ideally, a neurologist or specialist physician should confirm a diagnosis of MS. The basis of that remains a careful neurological assessment, including analysis of symptoms and a physical examination. It depends on the demonstration of typical features and exclusion of other disorders that may produce similar symptoms.
Diagnostic tests have an important role and include:
- Magnetic Resonance Imaging (MRI)—this is scanning of the brain and spinal cord. MRI has been a major advance in the diagnosis of MS, but the changes seen are not always specific for MS and age-related changes may cause confusion.
- Lumbar Puncture to examine the cerebrospinal fluid (CSF).
- Evoked Potentials—these measure electrical conduction through CNS pathways but are not commonly used now that MRI is widely available.
What are the Types of MS?
In general three typical patterns of MS can be recognised:
- Relapsing-remitting MS—relapses with a flare up of old symptoms or the development of new ones (over several days or weeks) are followed by a remission with resolution or reduction of symptoms.
- Secondary-progressive MS—after an initial course of relapsing/remitting MS, there is the development of slowly progressive disability (over several years). In this phase relapses may also still occur.
- Primary-progressive MS—in about 10% of cases, right from the beginning there is slow progressive worsening of symptoms and disability without distinct attacks.