Shayna Perrin, of Greymouth Junior High School, asks :-

How is epilepsy triggered?

Graeme Hammond-Tooke, a neurologist at Dunedin Hospital, responded.

Epilepsy is a condition where a person has recurring seizures. There are many different types of seizures but the most common is the tonic/clonic seizure (grand mal) where a person falls to the ground unconscious, goes stiff, then shakes and gradually wakes up. Another type of seizure is a petit mal or absence where a person goes blank for a few seconds without collapsing to the ground.

Seizures are thought to be due to a disorderly firing of large numbers of nerve cells. When the brain is being used nerve cells fire electrically in a complex sequence. During a seizure, large groups of nerve cells fire simultaneously. In epilepsy these nerve cells are unstable, and more likely to fire.

Many situations can trigger seizures. Sometimes there is an inherited tendency for this to occur. In other cases there is an underlying brain disease such as a brain tumor, stroke, brain injury or infection. In most cases, however, no specific cause is found. In someone with epilepsy, seizures may be more likely to occur under certain circumstances. Flashing lights, deep breathing, too much or too little sleep, and certain drugs and alcohol may act in this way. The abnormal activity can be demonstrated by placing a number of electrodes over the scalp to record the changes in the electrical activity of the brain. This machine is called an electroencephalograph.

Epilepsy is usually treated by drugs which suppress the abnormal electrical activity in the brain.