Epilepsy is best regarded as the symptoms of some underlying brain dysfunction, which causes gross misbehaviour of brain cells, either at a specific place (focal epilepsy), or more widely (generalised epilepsy). This misbehaviour causes physical consequences, like the loss of consciousness, or loss of muscle control.
Classifying epilepsies is a difficult task. It is useful for neurologists to group epilepsies into different types, but the reality is more complex. Each epilepsy is a malfunction of a particular area of the brain and is different for each child. As a result, there is not a set of well defined epilepsies, but rather a landscape in which the various peaks represent neurologically identified types like infantile spasms while individual symptoms merge into one another as imperceptibly as the hills in a landscape.
The landscape of epilepsy is even more confusing, because of the variety of symptoms (fits), the variety of underlying neurological deficits, and the variety of events which can cause epilepsy, ranging from genetic disorders, to diseases to physical trauma. As a result, there is a whole jumble of types of epilepsy that have been distinguished, and not an ordered taxonomy. A proper categorisation of epilepsy will only be possible when there is much better understanding of the underlying causes and of the structure and operation of the brain itself.
The following is a broad categorisation of the main types of epilepsy.
These are epilepsies with a clearly defined focal area within the brain. As a result, they have highly characteristic symptoms, such as visual hallucinations, or motor difficulties on one side of the body.
Generalised idiopathic epilepsies
Generalised epilepsies are those which have no defined focal area within the brain; as a result they have generalised symptoms as the whole brain becomes affected. Idiopathic is a medical term meaning that there is no clear environmental cause for the epilepsy and it is presumed that genetic factors predominate. There are usually no other handicaps and the EEG is often normal between fits. The response to drug treatment is usually good.
Generalised symptomatic epilepsies
Generalised epilepsies are those which have no defined focal area within the brain; as a result they have generalised symptoms as the whole brain becomes affected. Symptomatic is a medical term meaning that there is some structural abnormality in the brain, either present at birth or occurring later in life. Other disabilities may be caused by this same abnormality (physical, intellectual or psychiatric). EEG investigations may reveal the abnormality and the response to drug treatment is variable in different individuals. (Some individuals have cryptogenic epilepsy, which is epilepsy in which no cause can be found, even though a cause is suspected.)
This, of course, is the grouping for epilepsies which do not fit the classification schema.
What causes epilepsy?
Up to 2% of the population are diagnosed with epilepsy. This figure includes everyone who takes anti epileptic drugs or who has experienced an epileptic fit during the previous five years. Because the stigma still surrounding epilepsy obscures the actual number of people affected and many with the disorder may be reluctant to seek treatment, the actual percentage may be higher.
In approximately 75% of cases, there is no known cause. In the other 25%, the most common causes are:
return to Infantile spasms and other epilepsies
continue to Infantile spasms
(update 1.1: 8 November 2002)
(issue 1: 24 March 1998)