In someone with established epilepsy, the EEG between seizures may also show abnormal discharges which are not apparent to the doctor in terms of observed behaviour, nor are they associated with any change perceived by the person with epilepsy. Although the abnormal discharges of the EEG are clearly a fragment, as it were, of a seizure, they are not usually regarded as seizures. Our definition of an epileptic seizure, therefore, is a paroxysmal discharge of cerebral nerve cells apparent to the person and/or an observer.
Anything which increases the excitability of a group of nerve cells may cause a paroxysmal discharge. For example certain gases or chemicals, developed for use in war, are designed to cause disabling seizures amongst the enemy.
Does epilepsy stop? There is one encouraging point that all those with epilepsy must remember—the number of people who have epilepsy at any one time is much less than those who have had epilepsy in the past. An approximate estimate of the average duration of epilepsy can be obtained by dividing the average prevalence by the average annual incidence. This gives a figure of about 11 years. However artificial this figure may be, it underlines the point that epilepsy can and does usually stop. A great number of people with epilepsy fare better.