GBS is an illness that affects about 1200 people every year in the UK. Any one can be affected from babies to the elderly. Slightly more men than women contract the illness. CIDP is rarer though accurate figures are hard to obtain.

GBS and CIDP are not illnesses that you can 'catch'. It seems most likely that GBS and CIDP are caused by the body reacting incorrectly to a previous illness, usually a very minor one. Sometimes the previous illness may be the result of a virus (such as a cold) or the result of a bacterium (such as found in under-cooked food).

The body is designed to fight these 'bugs' but very rarely things go wrong and the body fights itself by mistake. This could be because parts of the body are very similar to the 'bug' and the body gets confused. The part of the body designed to fight invading 'bugs' is called the immune system.

Another important system in the body is called the nervous system. The nervous system is very complicated and often described as being in two main parts. The Central Nervous System comprises the brain and spinal cord. The Peripheral Nervous System comprises the nerves and the nerve fibres that radiate out from the central nervous system to the other parts of the body.

Motor peripheral nerves carry impulses away from the central nervous system to make muscles work. Sensory peripheral nerves carry impulses from sensory receptors (such as touch and heat receptors) to the central nervous system.

If the immune system fights the peripheral nerves by mistake, the individual nerve fibres become inflammed and stop working properly. Because the nerves to the feet and hands are the longest, the first symptoms of GBS and CIDP are usually felt first in the limbs. These symptoms are weakness (motor nerves) and pins and needles (sensory nerves).

As the illness progresses and more damage is done to the nerves, the symptoms appear to move up the limbs. Sometimes weakness becomes paralysis and the pins and needles can become very painful.

If this all happens in a short period, the illness is acute and called GBS. If it happens over a long period, the illness is chronic and called CIDP.