The brain is a complex organ consisting of over 100 billion interconnected nerve cells, which process and store information; this network of nerve cells generates our thoughts and emotions, controls our movements and senses our environment.
The nerve cells have a main body with branches called dendrites that detect certain chemicals and a projecting fibre called an axon. When the nerve cell is sufficiently ‘excited’, it fires an electrical impulse down the axon, resulting in the release of chemicals at specialised terminals, and these chemicals can either excite other nerve cells or can act to prevent (inhibit) other nerve cells from being excited.
If there were only excitation in the brain, then all the nerve cells would start to fire together, resulting in an ‘electrical storm’. If there were too much inhibition in the brain, then the brain would stop working. There is therefore a fine balance of inhibition and excitation necessary for the brain to function.
In a seizure, something disturbs this balance resulting in too much excitation and an ‘electrical storm’ occurs. This may occur in one part of the brain termed a focal seizure or throughout the brain, termed a generalised seizure. When the electrical storm starts in one area, it can spread to other parts of the brain. The nature of the seizure depends upon where the seizure starts and how far and fast it spreads.
As an example, a seizure that starts in the area of the brain controlling movements of the hand can start with jerking of that hand but, as the seizure spreads, all the limbs can start jerking and the person loses consciousness, or if a seizure starts in the area controlling emotion then there may be a sudden, strong feeling of fear and as the electrical storm spreads the person may lose awareness of their surroundings.
Seizures usually last less than a couple of minutes and afterwards the brain may not work properly for up to about a quarter of an hour, leading to confusion and disorientation for that period.