An epileptic seizure is a transient disturbance of consciousness, behaviour, emotion, motor function or sensation, due to abnormal electrical activity in the brain. Epilepsy is diagnosed if there:

• Are at least two unprovoked seizures occurring more than 24 hours apart
• Is one unprovoked seizure with the probability of further seizures similar to the general recurrence risk after two unprovoked seizures, occurring over the next 10 years
• Is a diagnosis of an epilepsy syndrome (more than 30 different epilepsy syndromes are recognised). Diagnosis is dependent on the underlying cause, seizure type, age of onset, family history, neurological findings, cerebral imaging and electroencephalogram (EEG) pattern.

Epilepsy most commonly starts in childhood, or in older people, and is more common in those with learning difficulties. There is no anatomically identifiable cause in about two-thirds of people with epilepsy.