For most people — six out of ten, in fact - there is no known cause of epilepsy and this is called idiopathic epilepsy. But sometimes the reason epilepsy develops is clear. It could be because of a severe blow to the head, a stroke, or an infection of the brain such as meningitis. Epilepsy with a known cause is called symptomatic epilepsy. Epilepsy can also be caused by drug and alcohol misuse, by conditions that affect the structure of the brain, such as cerebral palsy, by birth defects or by problems during birth which cause a baby to be deprived of oxygen (such as the umbilical cord getting twisted, or compressed, during labour).

Sometimes children below five years of age can have a seizure when they have a high fever. This is called febrile convulsion. If epilepsy occurs for the first time after the age of 20 years, it is usually symptomatic epilepsy, due to detectable brain damage such as a scar or healed wound in the brain, bleeding inside the brain, or damage because of long-term, excessive use of alcohol.

The diagnosis of epilepsy is mainly based on the description of the seizure given by the person themselves and any eye witness accounts. The box below provides examples of some of the questions you should ask the person and their family after a seizure has taken place.

A useful method for gaining insight into the recurrence of seizures is to encourage the person to keep a seizure diary (or mental record), noting the date, type of seizure, the time it occurred and its duration, and any thoughts they may have about possible epilepsy triggers or other relevant features.