MS The Disease
What is Multiple Sclerosis?
MS is a chronic inflammatory disease of the white matter of the central nervous system (CNS) - the brain and spinal cord. People with MS have patches of damage in the white matter. This damage, in the form of plaques or lesions, can result in partial or, occasionally, total loss of bodily functions controlled by areas of the CNS.
The signs and symptoms of MS are variable, but can include numbness, pain, pins and needles, muscle weakness or spasms, blurred vision, and fatigue, to name just a few. For some people, MS can come and go, otherwise known as periods of relapse and remission. For others, the disease can be progressive. It always makes life unpredictable for everyone affected.
MS affects 1 in 1,000 people in Western countries (USA, Europe and Australia) (refM1), and is generally more common in Caucasians. It also seems to be related to how far a country is from the equator, becoming more common the farther away a country is. MS usually starts between the ages of 20 and 40 years and affects about twice as many women as men (refM2).
Function of the CNS and White Matter
The CNS is made up of the brain and the spinal cord. It is a kind of computer that keeps us in touch with the world around. Through the CNS we can pick up signals from the outside world such as what we can see, smell, taste, hear and feel. The CNS also coordinates all our conscious and unconscious activities such as moving, talking, thinking, remembering and the reflex actions that happen without us thinking about them.
The CNS contains many neurons, the body’s controlling cells. These neurons perform many functions, such as transmission of information and control of bodily functions. Put simply, neurons are made up of three parts:
- Cell body.
- Dendrites, which are responsible for receiving information from other neurons and the body.
- Axons, or nerve fibres. The importance of the axons is that very weak electrical signals travel along them; in this way, information and instructions are passed from the CNS to the body.
When looked at with the naked eye, areas where the cell bodies and dendrites are clumped together in the tissues of the CNS look grey. For this reason, they are known as 'grey matter'.
The white matter includes those parts of the CNS where the axons are enclosed in ' myelin'. Myelin is a fatty substance made up of cell membranes; this substance is wrapped many times around the axons (see the figure below) (refM3). Myelin works like a kind of insulation around the axons, enabling information and instructions (electrical signals or impulses) to be sent more quickly from the brain to the rest of the body, or from a particular part of the body back to the brain.
The figure shows an axon (or nerve fibre) (red-coloured) in cross-section, with the myelin wrapped around the axon in several thin layers, forming a sheath. In reality, there are many more myelin layers than shown here.
