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22 November, 2009

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Epilepsy - seizures explained

Epilepsy is a condition in which a person has a tendency to have recurring seizures. Many people experience only one seizure, while about 50 per cent go on to have additional seizures. The people who have more than one seizure are usually diagnosed with epilepsy. Between three and five per cent of Australians will experience epilepsy during their life.

The brain controls the body’s actions, sensations and emotions through nerve cells (neurones) that carry messages between the brain and the body. These messages are confused by a seizure, which is a sudden disruption in normal brain activity, resulting in unusual movements, odd feelings or changed behaviour.

Seizure types
Many people think that the word ‘seizure’ means a convulsion, where someone becomes unconscious and falls, with their limbs jerking. However, this is just one type of seizure called a tonic clonic seizure (grand mal, or fit). There are many different types of seizures. Some people may have episodes where they ‘go blank’ for a few seconds or minutes. Some people remain fully conscious during a seizure and can describe their experience. For others, consciousness is affected and they are confused when the seizure ends. A seizure may involve the whole brain (generalised seizure) or part of the brain (partial or focal seizure).

Generalised seizures
There are several types of generalised seizures:

Tonic clonic seizure – the muscles suddenly stiffen and the person may fall. Rhythmic jerking follows. The person may bite their tongue or become incontinent. They are often confused afterwards.
Absence seizure – these occur mostly in children. The person will go ‘blank’ for a brief time during which they may stare and the eyelids may flicker. These seizures are often not noticed by other people.
Tonic – the body stiffens and the person may fall, sometimes causing injury. Recovery is usually quick.
Atonic – a sudden loss of muscle tone causes the person to fall, sometimes causing injury. Recovery is usually rapid.
Myoclonic – abrupt and brief jerking of one or more limbs.

Partial seizures
Only part of the brain is affected during a partial seizure. The signs and symptoms will depend on which part of brain the seizure comes from, and which body functions are controlled by that part of the brain. Signs and symptoms can vary from person to person.

Simple partial – the person remains conscious, but they may have unusual sensations or movements.
Complex partial – the seizure may begin with an odd taste or smell, a rising feeling in the stomach, or a sense of d�j� vu. This may be followed by a loss of awareness during which the person may make movements such as chewing or tapping. The person is often confused after the seizure.

Causes of seizures
The cause of seizures is not always known. Known causes include:

Brain injury
Brain infection
Structural abnormalities of the brain
Fever
Certain drugs
Excessive alcohol use
Genetic factors.

Seizures may appear to be brought on by a ‘trigger’ such as lack of sleep or significant stress. However, these ‘triggers’ alone do not explain why a seizure has occurred. Tests are still required to ensure no other cause can be found. It appears that certain people are simply more prone to having seizures than others. This is sometimes referred to as having a ‘low seizure threshold’ and may be due to their genetic makeup. In many cases, despite investigation, the cause of the seizure cannot be explained.

Diagnosis
It is not always easy to know if a person has had a seizure, and information from tests alone cannot confirm that a seizure has occurred. In some people, all the tests are normal, but – based on their history – the doctor is certain the person has had a seizure. A variety of methods may be used to diagnose the cause of seizures:

Medical history, including a detailed account of the event
Physical examination
Pathology tests
Electroencephalogram (EEG)
Computed tomography (CT)
Magnetic resonance imaging (MRI).

Although medical examinations may help identify the cause of a seizure, in many cases the cause of a seizure cannot be determined.

Treatment
Medication can often prevent seizures from recurring. However, it is not prescribed for everyone who has a seizure. Whether or not to prescribe medication will depend on the risk of that person having further seizures.

Where people are considered to be at risk of recurring seizures and medication is prescribed, approximately 70 per cent are likely to achieve seizure control. Where several medications are tried and seizures are not controlled, surgery may be a treatment option in some cases.

Safety issues
Although many people who witness a seizure fear that the person may be harmed by the event, the risk of brain damage or death from a seizure is low. Following a first seizure, the highest risk of having another seizure is during the three months after the first seizure. The doctor will recommend guidelines in relation to driving and other dangerous activities.

Where there is a risk of a seizure, people are advised to swim with a companion or observer. Showers are recommended instead of baths and special care should be taken when using hot water or items that can cause burns. Turning on the cold tap first in the shower, bath or basin and lowering the temperature of the hot water service are good safety hints for any home. Risks are minimised by following the recommended treatment plans and ensuring that accurate first aid information is available to those who might need it.

Seizure first aid
If you are with someone who has a convulsive seizure, you should try to:

Stay calm and remain with the person.
Time the seizure.
Protect the person from injury – remove any hard objects that are near the person.
Place something soft under the head and loosen any tight clothing at the neck.
Gently roll the person onto their side as soon as it is possible
to do so and firmly push the angle of the jaw forward to assist with breathing. If breathing seems difficult, check the mouth to make sure that food or dentures are not blocking the airflow.
Establish communication with the person so you know they have regained consciousness.
Reassure the person and minimise embarrassment during recovery.
Stay with them until they recover; this may range from five to 20 minutes.

Do not:

Put anything in the person’s mouth or between the teeth
Restrain the person unless they are in danger
Give pills, food or drink until recovery is complete.

If the person is in a wheelchair
If the seizure occurs in a wheelchair, car seat or stroller, leave the person seated as long as they are secure and safely strapped in. Support their head. When jerking stops, if the person is unconscious, remove from seat and roll them onto their side. Follow the steps for general seizure first aid.

If the person is in water
If the seizure occurs in water, support the person in the water with their head tilted so it stays above the surface. When jerking stops, remove the person from the water and check to see if they are breathing. If they are not breathing, start CPR immediately, then call an ambulance.

Even if the person appears to be fully recovered, you should still call an ambulance. The person should have a full medical check-up as inhaling water can cause lung or heart damage. The person should not continue with swimming or water sports that day, even if the person appears to be fully recovered.

You may need to call an ambulance
You should dial triple zero (000) to call an ambulance if:

The seizure lasts for five or more minutes or a second seizure quickly follows the first
The person is not conscious within five minutes of the seizure stopping
The person does not fully recover after the seizure or has trouble breathing
The seizure occurs in water
The person has ingested food or vomit
The person is injured
The person is pregnant or has diabetes
You believe it is the person’s first seizure or you do not know – this applies regardless of how long the seizure lasts
You are in doubt.

When the person doesn’t have a convulsion
In the case of a non-convulsive seizure, the person may simply appear confused. Reassure the person and gently guide them away from harm. You should call an ambulance if:

The person is not starting to recover from the seizure after 15 minutes
The person has diabetes
The person is injured
You believe it is the person’s first seizure or you do not know – this applies regardless of how long the seizure lasts.

Where to get help

Your doctor
In an emergency, dial triple zero (000) for an ambulance
Epilepsy Foundation of Victoria Tel. (03) 9805 9111
Epilepsy Helpline Tel. 1300 852 853

Things to remember

A seizure is a sudden disruption to normal brain activity, which causes unusual movements, odd feelings or changed behaviour.
Many people will only ever have one seizure, but approximately 50 per cent will go on to have more seizures. Those who have more than one seizure are usually said to have epilepsy.
The cause, type and treatment of seizures vary from person to person.
If a convulsive seizure lasts for five minutes or longer, or you believe it’s the person’s first seizure, call 000 for an ambulance.

You might also be interested in:
Nervous system.
Neuromuscular system.

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