What is an epileptic seizure?

Epilepsy is the world's most common - yet treatable - neurological disorder; 50 million people worldwide are affected. The disorder is more common among men. About 50 percent of people who develop epilepsy do so before the age of 15 years. The incidence increases again after the age of 65 years.

Brainwave, the Irish Epilepsy Association, estimates that there are at least 25,000 people with epilepsy in Ireland. Although these figures show that it is almost as common as diabetes, epilepsy is much less understood or discussed. As a result, it is feared and still carries a social stigma.

An epileptic seizure, often referred to as a fit, occurs when there is an abnormal discharge of neurones in the brain. Some seizures are triggered by lights flashing at a particular frequency, physical or emotional stress, allergies and tiredness.

The type of seizure experienced depends on what area of the brain is affected. There are two broad categories of seizures - partial seizures and generalised seizures.

Partial seizures

Partial seizures occur in a wide variety of forms. The disturbance in brain activity occurs in a distinct part of the brain. Therefore, the part of the body affected by the seizure depends on the part of the brain involved.

Partial seizures are usually confined to either twitching of one limb or to part of a limb, or to unusual tastes or sensations such as pins and needles in a distinct part of the body. However, in some instances the abnormal activity spreads to other parts of the brain so that the seizure becomes generalised.

Partial seizures may be either simple or complex. In simple partial seizures there is no loss of consciousness. The person may experience a warning of an impending attack such as an abnormal smell or taste before the seizure starts. This is known as an "aura". The type of aura experienced depends on the area of the brain affected.

In complex partial seizures there is a change in awareness, semi-purposeful movements (fiddling with clothes or nearby objects), wandering and general confusion.

Generalised seizures

Generalised seizures involve most of the brain from the start and usually cause immediate loss of consciousness. There are several types of generalised seizures.

Generalised tonic-clonic seizure (Grand mal seizure) are the type of seizure most people think of as being associated with epilepsy. They are major convulsive seizures that may occur spontaneously or develop from a partial seizure.

The individual may cry out before becoming rigid and falling to the ground. The muscles then relax and contract alternately in a jerky fashion causing the person to convulse. During the tonic phase breathing may stop and the skin may turn slightly blue. During the clonic phase breathing is laboured. The tongue may be bitten. Incontinence of urine and faeces may occur.

The individual slowly recovers consciousness after the seizure. There is initial confusion, headache, aching limbs and a desire to sleep before control returns.

Other common types of generalised seizures include atonic seizures (drop attacks), during which there is a sudden loss of muscle tone causing the individual to fall down and tonic seizures, which involve generalised stiffening of the muscles without the jerky movements. The person may fall to the ground if standing. By contrast, myoclonic jerks involves an abrupt jerking of the limbs. They are not usually associated with loss of consciousness unless accompanied by absences. Absences, also referred to as petit mal are sudden, short moments during which the individual looses consciousness or awareness of what is going on around them. Usually they return to normal quite quickly. There may be no other signs of a seizure except fluttering of the eyelids. This type of seizure occurs most commonly in children. Such attacks may occur very frequently and can cause difficulty in concentrating at school.

Seizures are usually self-limiting but occasionally they occur in a series or without interruption. This is termed status epilepticus. Any of the seizure types can occur in series. These patients are usually known to have epilepsy.

Generalised tonic clonic status epilepticus is the most serious form of epileptic seizure and is regarded as a medical emergency. It is usually precipitated by withdrawal of or non-compliance with anti-epileptic drug therapy, infections such as encephalitis, meningitis or brain absces and brain tumour.


Written by Medpages Editorial Team
Last Editorial Review: 21/1/2010