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Lennox-Gastaut Syndrome


What is a syndrome?

A syndrome is a group of signs and symptoms that, added together, suggest a particular medical condition. In epilepsy, examples of these signs and symptoms would be things like the age at which seizures begin, the type of seizures, whether the child is male or female and whether the child has physical or learning difficulties, or both. The results of an electroencephalogram (EEG) are also used to help identify epilepsy syndromes.

Epilepsy Action has more information about seizure types, learning disabilities, and the EEG.

If you would like to know more about an epilepsy syndrome, please speak to your doctor. If you would like to know more about epilepsy in general, please contact Epilepsy Action.

Lennox-Gastaut Syndrome

This type of epilepsy is uncommon and occurs in between one and five in every 100 children with epilepsy. However, it is the most common cause of intractable (difficult to treat) childhood epilepsy. The most common time for it to start is between three and five years of age.


The seizures experienced can vary.

The most common type is atonic seizures or ‘drop attacks’. During these, the child will suddenly fall to the ground which may at first be mistaken as tripping up or poor balance. These seizures usually happen many times a day and are very upsetting as the child is often injured during them.

Another common seizure type is atypical absence seizures, which can last from 10 seconds to several minutes. During these seizures the child will appear vacant or blank. They may have other features like head nodding, or rapid blinking. The child may have some awareness of what is going on around them.

These seizures can be very frequent and can even merge to be constant, forming a state called ‘non-convulsive status epilepticus’. During these episodes the child will ‘not be with it’, drool, be unable or slow to speak, need help with feeding and be floppy or wobbly.

Another frequent seizure type is tonic seizures. They may only happen at night. There is a general stiffening of the arms and legs.

Children with Lennox-Gastaut syndrome may have other types of seizures including generalised tonic-clonic seizures, partial motor seizures, complex partial seizures and myoclonic seizures.

All children with Lennox-Gastaut syndrome will develop learning difficulties which will be moderate to severe. Some children will have developmental delay or learning difficulties before the seizures start.

About two out of ten children will develop Lennox-Gastaut syndrome after having West syndrome (infantile spasms).


The diagnosis becomes clearer with time. The electroencephalogram (EEG) is very helpful as typical abnormalities are seen, even when the child is not having any obvious seizures.

Some children may have a cause which can be identified. These include a genetic condition called tuberous sclerosis, a structural brain malformation, brain damage due to problems before or around the time of birth), meningitis as a young baby or a head injury. In about half of all children with Lennox-Gastaut syndrome, no cause can be found.


Treatment of Lennox-Gastaut syndrome is very difficult. The drugs which may be effective in some cases include sodium valproate, lamotrigine, topiramate, clobazam and phenytoin.

Sometimes the ketogenic diet may be effective.

Courses of corticosteroid drugs are sometimes used when seizures are particularly difficult to control.

In children who have repeated drop attacks surgery may be helpful. Corpus callostomy and Vagus Nerve Stimulation (VNS) are two surgical procedures that may be considered.


The long term prognosis is poor in terms of seizure control and intellectual development.

A very small number of children will outgrow their seizures by their teenage years. However, the remaining children will continue to have seizures, often on a daily basis, into adult life. These patients will be dependent on others for all their life.

Some children will develop problems like repeated or severe chest infections which may shorten their life.


Lennox-Gastaut Support Group
9 South View, Burrough on the Hill, Melton Mowbray, LE14 2JJ
Telephone: 01664 454 305.

Tuberous Sclerosis Association
P O Box 12979, Barnt Green, Birmingham, B45 5AN
Telephone: 0121 445 6970
Website: tuberous-sclerosis.org

Contact a Family
209-211 City Road, London, EC1V 1JN
Telephone 0808 808 3555
Website: cafamily.org.uk


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Our thanks

Epilepsy Action is indebted to Dr Richard Appleton, a Consultant Paediatric Neurologist who specialises in children’s epilepsy, and to Dr Rachel Kneen, Consultant Paediatric Neurologist and Dr Stewart Macleod, Specialist Registrar in paediatric neurology, at Alder Hey at Alder Hey Children’s Hospital, Liverpool, who have kindly prepared the information on this page.

This information is exempt under the terms of The Information Standard.

  • Updated July 2012
    To be reviewed December 2015

Comments: read the 1 comments or add yours


We have recently started a UK website for Lennox-Gastaut Syndrome, it offers support and advice to those affected by LGS. We also have a Facebook group that families use to discuss experiences and ask questions.

Our website is www.lgsfoundation.org.uk

Submitted by Leah Jordan on