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The nervous system manages our actions through the transmission of electrical signals between the brain and other parts of the body.
The central nervous system processes information from the peripheral nervous system and sends instructions back.
For example if sensors in the skin detect you have touched a hot surface, muscles are instructed to react. This is called a reflex or involuntary action. Actions over which we have control through our own conciousness are called 'voluntary'.
We have 12 pairs of nerves attached to the brain and 31 pairs attached to the spinal cord making a total of 43 different pairs of nerves. These are all connected through the central nervous system to all parts of our body.
In the case of the spinal nerve, as it leaves the spinal area it divides into two branches. Then it sub-divides into many small branches to reach the muscles and the skin. So our bodies are covered with a network of nerves, reaching to every sensor and every muscle
When the peripheral nerves are damaged, this is called peripheral neuropathy and often just 'neuropathy' as peripheral neuropathy is the most common type. One of the most frequent causes is diabetes but other acquired or hereditary disorders, nutritional deficiencies, toxicity, autoantibodies and of course autoimmune and vasculitic diseases are also responsible.
As EGPA sufferers, we are not alone in experiencing peripheral neuropathy. It is very common, affecting around 1 in 50 people in the UK. The figures worsen with age so that 1 in every 10 people who are over 55 years old suffer to varying degrees. 
There is always an underlying reason for peripheral neuropathy. It is not a disease in its own right.
Neuropathies are therefore classified according to the cause and laboratory testing is usually required for identification.
If EGPA has already been diagnosed, then it is the most probable reason for peripheral neuropathy whereas if there is neuropathy with no pre-diagnosed reason, then statistically EGPA is unlikely to be the cause.
One of the classification criteria for EGPA is the presence of neuropathy.Next >>