What is Epilepsy?
Epilepsy is a relatively common disorder which takes the form of recurring seizures. A seizure occurs when there is a sudden, uncontrolled, surge in the normal electrical activity in all or part of the brain.
Epilepsy can affect anyone at any age but most people with epile psy will experience their first seizure before the age of twenty. It is estimated that more than 275,000 people throughout Australia have a diagnosis of epilepsy.
So, What is it?
Before answering this question, it’s necessary to look at the brain – and how it works.
The brain is made up of millions of tiny nerve cells called neurones, each of which can send and receive messages in a very similar way to one of the units in a computer or calculator. In the brain, messages are passed from cell to cell by various chemicals (known as neurotransmitters).
As a rule these messages are sent in an orderly way. If however, something unusual happens – if, for example, the ‘wrong’ message is passed or cells fail to res pond to a message – an epileptic seizure may result.
An epileptic seizure can therefore be described as a “temporary breakdown” in the brain’s communication system.
Epilepsy is present when a person has established tendency to having recurrent seizures.
Anybody Can Have A Seizure
The ‘temporary breakdown’ that causes a seizure can happen to anybody; it’s simply a matter of getting the necessary activator or stimulus to start it off. With the stimulus of an electric current, for example, everyone would have a seizure. Some people, however, require comparatively less of a stimulus than others, to trigger off a seizure. The likelihood of someone having an epileptic seizure is described as the ‘epileptic threshold’. People with epilepsy have a low epileptic threshold – which means they may have a seizure if the working of the b rain is only slightly upset. Others are able to withstand quite a strong stimulus to the brain without having a seizure; these people have a high threshold.
Thus having epilepsy can, in some ways, be compared to having an allergy. Some people clearly have a low allergy threshold – and only a slight amount of pollen in the air will make their eyes sore and make them start sneezing. With others, no amount of pollen seems to have any effect. The epileptic threshold.
The sorts of stimulus that triggers off seizures in different people, can vary enormously. In young children aged six months to three years, a high temperature can cause a seizure, known as a febrile convulsion. In women, for example, hormonal changes associated with the menstrual cycle, may lead to chemical changes which may, in turn, lead to chemical changes in the brain. In some people, these changes may be prompted by a visual stimulus, such as flashing lights. A change of daily routine or lack of sleep, or more emotional factors, such as stress and excitement, can all prompt seizures in some individuals. Very often however, it is impossible to say what exactly acted as a stimulus for a seizure; there is no cause that we can readily see.
What Does An EEG Show?
An EEG, or electroencephalogram, is a special recording of the tiny electric signals produced by the brain, that can provide important information about how the brain is working. It is a simple, harmless test, in which small discs are placed on the scalp and the activity of the brain is recorded.
The EEG can help doctors in diagnosis, as it may show the sort of abnormal activity commonly found in epilepsy. The recording will show for example, a special pat tern, known as a “spike” and “wave” pattern in many patients with a low epileptic threshold. Howeve r, a normal EEG does not exclude epilepsy as the electrical activity may only be abnormal during an attack. A doctor is certain to call for an EEG test if he/she suspects epilepsy.
Are Epileptic Seizures All The Same?
No – there are a number of different types and patterns of epile ptic seizures. The various names of the different seizures have often been a source of confusion in the past.
Seizures Are Divided Into Two Main Groups:
Partial seizures – only part of the brain is involved.
Generalized seizures – these involve most of the brain.
1) Focal Seizures
About 60% of people with epilepsy have Focal seizures. These seizures can often be subtle or unusual, and may go unnoticed or be mistaken for anything from intoxication to daydreaming. Seizure activity starts in one area of the brain and may spread to other regions of the brain.
Types of Focal seizures are:
Focal seizure – awareness retained
Focal seizures – awareness altered
2) Generalised Seizures
Generalised seizures are the result of abnormal activity in both hemispheres of the brain simultaneously.
There are many types of generalised seizures:
Tonic-clonic – characterised by alternative stiffness and jerkin g.
Myoclonic – characterised by muscular jerking.
Absence – in which the person loses awareness briefly.
