What is MS
What is MS?
Before reading the introduction to multiple sclerosis (MS), it is important for you to realise that there is no typical MS.
It is a very variable condition with no predictable or set pattern and symptoms can vary from person to person and for each person over time. Many people with MS continue to live a normal life and can go for long periods of time without developing any symptoms.
MS is characterised by a sudden onset of symptoms, also known as a relapse. The symptoms often improve after a few days or weeks and lead to either a full or partial recovery. This period is known as a remission.
Multiple sclerosis is a variable life-long condition, affecting many (multiple) sites of the central nervous system (CNS), leading to lesions and scars (sclerosis) within the brain and/or the spinal cord.
In our body, the central nervous system (CNS) – consisting of the brain and the spinal cord - acts as a centre of command, controlling muscle movements and gathering and interpreting incoming sensory information from the peripheral nervous system (PNS) – i.e. sensory and motor nerves (figure 1). Nerves allow for different parts of the body to communicate.
For example:
• On picking up a hot cup the peripheral nerves sense heat and tell the CNS
• The CNS decides to leave the cup to cool down
• The peripheral nerves tell the muscles in the arm to put the cup back down
Electrical impulses travel along the nerves allowing our brain to communicate with different parts of our body (figure 2). The nervous system can be tested by various automatic reflexes. Reflexes can, for example, be tested by tapping the knee or elbow with a small reflex hammer. Reflex function can help to identify neurological disorders.
Importance of myelin
In the brain and the spinal cord, our nerve fibres are wrapped in an insulating outer layer - a protective sheath called myelin - required to speed up transmission of electrical signals. Thanks to these fatty sheaths, impulses can jump from one periodic break in the myelin sheaths, called node, to the next node, thus enabling messages to be passed on at high speeds. (figure 3)
Loss of myelin and its consequences
In MS, myelin sheaths are injured by inflammatory processes. Such inflammatory reactions not only harm myelin but also oligodendrocytes (cells in charge of producing and maintaining myelin sheaths of axons in the CNS). Typically in MS, the site of inflammation can easily be spotted in MRI (magnetic resonance imaging) pictures of the brain.
From damage…
When the myelin is “eaten” by macrophages, the cleaning crew of the immune system, the axons of the nerves are left naked. Naked, i.e. demyelinated axons, however, cannot conduct electrical impulses efficiently.
When nerve fibres have been stripped, i.e. have been demyelinated, they may begin to “short circuit” or fail to properly transmit signals within the nervous system. Thus, when myelin sheaths are damaged, impulses are slower than they used to be.
Messages then have to be passed on along the entire length of the nerve fibres which is much slower than if impulses could still jump from node to node.
Transmission is slowed or even blocked.
When the inflammation subsides, repair mechanisms are set in motion, sometimes resulting in remyelination (restoration of myelin that was damaged).
This cycle of injury and recovery may occur over and over again in the nerves of the CNS. When the inflammation covers a large region, scars are left behind, which are referred to as plaques and can be detected by MRI as well. If inflammation occurs repeatedly in the same place, repair processes may not be able to keep up with restoration, resulting in permanent injury to those nerves.
Therefore, in people with MS, demyelination as well as remyelination occurs. The area of the brain or the spinal cord affected by these lesions determines which symptoms a person will experience.
…to symptoms
MS symptoms depend on the location of demyelination in the brain and the spinal cord. They may vary tremendously among individuals and are difficult to predict.
Many functions of the body can be affected. Some people with MS do not have any symptoms at all for a long period of time, and it may well be that despite injury to certain nerve pathways the brain is able to compensate by re-routing nerve impulses to alternative nerve pathways.
In other cases there is a connection between the injured region and the probability that symptoms will appear. So it is important to remember that most people will only experience some of the common symptoms of MS.
Common symptoms in people with MS include:
• Abnormal sensations - some people with MS experience strange sensations, such as feeling cold, numbness, tingling or itching
• Visual disturbances - such as blurred vision or loss of colour perception mostly only in one eye
• Fatigue - one of the most common symptoms of MS. A continuous tiredness that does not correlate with levels of neurological disability or MRI lesions but that is associated with depression
• Motor dysfunctions - such as stiffness, weakness, loss of muscle strength, spasticity of the limbs
• Problems with balance - difficulty in walking or trembling
• Bowel and bladder problems - such as problems with bladder emptying and constipation
• Sexual problems - such as impotence or loss of sensitivity
• Pain - acute pain (e.g. behind the eye) or chronic pain (e.g. extremities or back) is reported by a large number of people living with MS at some time or another
These symptoms can lead to depression. This is not uncommon with MS.
Most of these problems can be reduced by a number of therapies and drugs. You should contact your doctor who can then advise on the best possible therapeutic approach in your particular situation. Some symptoms are seen often, others only rarely. However, even when somebody has no symptoms at all, MS may still be “silently” active.
