Absence seizures

What is an absence seizure?

Absence seizure (previously called petit mal) is a form of generalised seizure. An absence seizure mainly occurs in children and young people. Absence seizures are uncommon in adults.

Many people associate epilepsy with the dramatic convulsive type of seizure, when people lose consciousness and have uncontrollable shaking of their arms and legs. Absence seizures are not like this. They are often not noticed for some time, as it can appear that the affected person is simply daydreaming. The following gives a typical example of an absence seizure:

• The person has a brief loss of consciousness (an absence) for a few seconds.

• They do not fall but may pause in what they are doing.

• Their face often looks pale with a blank expression.

• They may look dazed, the eyes stare and the eyelids may flutter a little.

• Sometimes their head may fall down a little, or their arms may shake once or twice.

• Each seizure usually starts and finishes abruptly. The person is not aware of the absence and resumes what they were doing.

Absence seizures may not be noticed by parents or teachers for some time, as they usually last just a few seconds. It is common to have several absence seizures per day. If they are frequent, a child's education may suffer, as they will not be able to concentrate on lessons.

No underlying cause for absence seizures can usually be found in the brain. The bursts of abnormal electrical activity usually occur for no apparent reason. Why absence seizures start, or continue to occur, is unclear. What seems to happen is that the brain develops a low threshold for bursts of abnormal electrical activity.

In some people, a tendency to develop absence seizures is inherited. How it is passed on is not clear but several members of an extended family may have this type of epilepsy. The parents of children with this type of epilepsy may wish to have genetic counselling to see if there is a chance of further children being affected.

The most important part of making a diagnosis is to have a clear description from parents or teachers of what happens during a suspected absence seizure. Often the description is typical of an absence seizure.

However, sometimes it can be difficult for a doctor to be sure. The electroencephalograph (EEG) test is then helpful. This records the electrical impulses from the brain. Special stickers are put on parts of the scalp. They are connected to the EEG machine which amplifies the tiny electrical impulses given off by the brain and records their pattern on paper or a computer. The test is painless. People with absence seizures often have a typical EEG pattern.

There are several different medicines that can control absence seizures. They work by stabilising the electrical activity of the brain.

Medication needs to be taken each day to control seizures. In most cases, one medicine can control seizures. A low dose is usually started at first. If this fails to control seizures, the dose may need to be increased or even changed to an alternative medication.

A medicine called ethosuximide is recommended as first choice for absence seizures. Alternatives include sodium valproate, lamotrigine or levetiracetam. Sodium valproate is usually avoided in people under the age of 55, as it can cause birth defects and developmental problems in children of people who are taking it whilst pregnant, or possibly if they are taking it when they conceive a child.

See the separate leaflet called Epilepsy medication and side-effects.

The outlook (prognosis) is good. Absence seizures rarely continue into adulthood. This type of epilepsy is not usually associated with any other brain (neurological) condition. Children with this type of epilepsy have the same range of intelligence and other abilities as other children. Treatment usually controls the seizures so that education and other aspects of life can be normal. Absence seizure treatment can often be stopped in the teenage years.

However, some children with absence seizures will have persistent seizures or develop other types of seizures (such as convulsive seizures (tonic-clonic seizures) later in life).

For more information, see the separate leaflets called Epilepsy and Types of seizures.