A seizure occurs when the brain receives a burst of abnormal electrical signals that temporarily interrupt its normal electrical function. There are many different types of epileptic seizure. The signs of a seizure are varied and include occasional interruptions to consciousness during absence seizures (small generalised or petit mal seizures), brief involuntary muscle jerks with no loss of consciousness (myoclonic seizures) and violent convulsions with loss of consciousness (grand mal or tonic clonic seizures).
Epilepsies can occur as the result of a stroke or head injury, among other causes, or may be provoked by a brain tumour or degenerative condition such as Alzheimer’s Disease. Around one third of epilepsies are due to genetic factors. Only a small proportion of these epilepsies are inherited – many develop as the result of a genetic mutation occurring for the first time (de novo mutations). Sometimes, however, the cause of epilepsy remains unclear.
Not every person who has one or more epileptic seizures has epilepsy. Epilepsy is not usually diagnosed until the person has had several spontaneously occurring seizures with no identifiable trigger. Epilepsy is not a uniform condition but rather a group of disorders with very different symptoms, progressions and causes.