Epilepsy
To understand how epilepsy arises, we must briefly outline how the brain functions normally.
The brain consists of millions of nerve cells, or neurones, and their supporting structure. Each neurone maintains itself in an electrically charged state. It receives electrical signals from other neurones, and passes them on to others. What actually happens is that a tiny quantity of a special neurotransmitter substance is released from the terminals of one neurone. This chemical excites an electrical response in the nuerone next in the chain, and so the signal moves onward.
All the functions of the brain, including feeling, seeing, thinking and moving muscles depend on electrical signals being passed from one neurone to the next, the message being modified as required. The normal brain is constantly generating electrical rhythms in an orderly way.
In epilepsy this order is disrupted by some neurone discharging signals inappropriately. There may be a kind of brief electrical "storm" arising from nuerones that are inherently unstable because of a genetic defect (as in the various types of inherited epilepsy), or from neurones made unstable by metabolic abnormalities such as low blood glucose, or alcohol. Alternatively, the abnormal discharge may come from a localised area of the brain (this is the situation in patients with epilepsy caused by head injury, or brain tumour).
