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generalised tonic-clonic seizure

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Alternative Names
grand mal seizure

These seizures are marked by a sudden loss of consciousness with violent muscle contractions of the limbs and trunk. There may be a loss of bladder control and some injury to the mouth.

What are the signs and symptoms of the condition?
Convulsions (repeated jerking movements) of the limbs and trunk begin suddenly. The seizures usually last less than 3 minutes. If the seizures last much longer, the individual may be in status epilepticus (prolonged seizures or repeated seizures without waking up in between). After the seizure, the person is unresponsive, usually for less than 10 minutes. Confusion or sluggishness may follow.

What are the causes and risks of the condition?
Seizures that have a clear and obvious cause are called provoked seizures. The causes may be drug toxicity, alcohol withdrawal, concussion (injury caused by a blow to the head) or fainting. Unprovoked seizures have no clear cause and when unprovoked seizures occur, there may be underlying epilepsy (seizure condition in which no obvious cause is found). In this case, electroencephalography and brain imaging studies should be done, along with a complete neurologic history and examination.

How is the condition diagnosed?
Diagnostic tests are electroencephalography (EEG) (recording of brain waves) and brain imaging studies, such as magnetic resonance imaging (MRI) (special three-dimensional image using magnets) or computed tomography scan (CT) (special three-dimensional xray). EEG may be delayed for 7 to 10 days. Basic metabolic (blood tests for sugar, sodium, thyroid hormone, and other chemicals) studies should be done. Serum calcium and magnesium should be measured. If the person has a fever, examination of cerebrospinal fluid (clear fluid surrounding the brain and spinal cord) and a full blood count (FBC) (measure of the red blood cells, white blood cells, and platelets) may also be done.

What are the long-term effects of the condition?
Status epilepticus occurs with a first seizure of this type 12 to 15% of the time.

What are the treatments for the condition?
If the examination, the history, the EEG, or the imaging studies are abnormal, antiepileptic drugs are usually given. These drugs include: phenytoin, carbamazepine, valproate sodium, and phenobarbital. Other drugs are lamotrigine, topiramate, and tiagabine. If all parts of the evaluation are normal, drugs are usually not given after a first seizure of this type. If the evaluation is normal, the risk of the condition recurring is 14% for 1 year and 34% for 5 years.

What are the side effects of the treatments?
Side effects depend on which drugs are used. The most common are sluggishness, ataxia (loss of co-ordination), confusion, allergic rashes and liver abnormalities.

What happens after treatment for the condition?
About 80% of people treated for epilepsy get good control of their seizures.

How is the condition monitored?
People who have had seizures are watched for recurring seizures and side effects of antiepileptic drugs.

Author: Gerald C. McIntosh, MD
Reviewer: HealthAnswers Australia Medical Review Panel
Editor: Dr David Taylor, Chief Medical Officer HealthAnswers Australia
Last Updated: 1/10/2001
Potential conflict of interest information for reviewers available on request

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