Epilepsy is a condition in which people have epileptic attacks (also known as seizures). It is one of the more common neurological conditions, affecting 0.5-1 per cent of the population. Epilepsy is not a single condition, but a group of conditions with differing causes, treatments and prognoses.

Not all seizures are due to epilepsy. For example, drugs prescribed by doctors for other conditions - as well as substances such as alcohol - can sometimes cause seizures.

At present, most doctors would not diagnose a patient as epileptic if they had only suffered a single seizure. This is because epilepsy is defined as a condition in which patients have recurrent seizures.

The brain is made up of a vast number of nerve cells (neurones) which communicate with each other through electrical signals. The interplay between these neurones has to be carefully regulated for the brain to function properly.

Epileptic attacks happen when an abnormal electrical discharge occurs in the brain, disturbing its normal function. The type of seizure depends upon where this takes place, and how much of the brain is affected. During an attack, these discharges may cause:

• twitching of the muscles
• abnormal sensations (eg tingling on one side of the body or awareness of a strange taste or smell)
• emotional symptoms such as fear or 'deja vu'
• loss of consciousness.

Epileptic attacks are usually brief, lasting from seconds to a few minutes. Once the attack is over, the normal electrical activity of the brain resumes.

Epilepsy can start at any age, although it tends to first occur in children and the elderly.