Lennox-Gastaut syndrome

Lennox-Gastaut is a rare epilepsy syndrome that causes regular seizures and learning difficulties. Most people who get this syndrome will have it for life. But support is available to help you and your child live with the condition.

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Who gets Lennox-Gastaut syndrome?

Lennox-Gastaut syndrome affects around 1 or 2 in every 100 children with epilepsy. The most common time for this syndrome to start is between 3 and 5 years of age. It can start as early as 18 months or, very rarely, as late as age 10 years of age.

Usually, children will be diagnosed with a different epilepsy syndrome first, which later becomes Lennox-Gastaut syndrome. About 1 in 5 children will develop Lennox-Gastaut syndrome after having infantile epileptic spasms syndrome (West Syndrome).

Most children who develop Lennox-Gastaut syndrome will already have developmental delays before they start having seizures.


What causes Lennox-Gastaut syndrome?

There are many causes of Lennox-Gastaut syndrome. These include:

  • Genetic conditions, caused by a change (or ‘mutation’) in a gene – like a condition called tuberous sclerosis complex
  • Problems with the structure of the brain or how it’s formed during pregnancy
  • Problems just before or during birth, like your baby doesn’t get enough oxygen during or just after their birth
  • Having certain infections, like meningitis, as a young baby
  • Brain damage following a severe head injury
  • Metabolic disorders – which cause problems with certain chemical processes in the body

In at least a quarter of children with Lennox-Gastaut syndrome, no cause will be found.


Children with Lennox-Gastaut syndrome will usually have different types of seizure. All children get tonic seizures. In a tonic seizure, your child’s body and limbs suddenly stiffen, and they fall down – sometimes causing an injury. You might notice their eyes roll backwards, or they might cry out first. These seizures usually happen many times a day. They can also happen during the night.

Other types of seizures your child may have include:

  • Atypical absence seizures – These cause your child to appear vacant or blank. They may nod their head, blink rapidly or turn their head slowly to one side. The seizure can last from a few seconds to several minutes. Atypical absence seizures that happen one after another can turn into non-convulsive status epilepticus. This can be a medical emergency and your specialist will talk to you about having an emergency care plan in place.
  • Atonic seizures – These cause your child to suddenly become floppy and fall down. This type of seizure usually only lasts for a few seconds.
  • Focal seizures – These are seizures that start on just one side of the brain. They can cause changes in movements, sensations, or stop your child from responding to you.
  • Generalised tonic-clonic seizures – These cause children to fall unconscious and make jerking movements with their arms and legs. The seizures normally last for 2 to 3 minutes. Sometimes they can last longer and become convulsive status epilepticus. This is a medical emergency and your specialist will talk to you about having an emergency care plan in place.
  • Myoclonic seizures – These cause sudden, jerking movements of the arms, legs or whole body. This may also cause the child to fall down.

If your child has seizures during the night, it can disturb their sleep. Nearly all children with Lennox-Gastaut syndrome also have learning difficulties and behavioural problems. These difficulties may already be there before the onset of seizures and will usually get worse over time.


Your child may be diagnosed with a different epilepsy syndrome first. The most common one is infantile epileptic spasms syndrome. From the age of 18 months or 2 years of age they will show more and more symptoms of Lennox-Gastaut syndrome.

Your child’s doctor may recommend a number of tests to confirm a diagnosis. These will include an EEG (electroencephalogram) to look at electrical activity in the brain. An EEG can be very helpful for diagnosing Lennox-Gastaut syndrome, as it often shows a typical pattern in children with this epilepsy syndrome.

Your child’s doctor may also recommend that they have an MRI (magnetic resonance imaging) scan to help with diagnosis. This may help to find any structural changes in your child’s brain that could have caused the syndrome.

Other tests could include blood and urine tests. These will be to look for a genetic cause or a metabolic cause of the syndrome.


Treatment for Lennox-Gastaut syndrome can be difficult, as many of the epilepsy medicines used for epilepsy seizures don’t work very well for this condition. But there are still treatment options and support available to help manage your child’s symptoms and difficulties. The National Institute for Health and Care Excellence (NICE) has guidelines for treating Lennox-Gastaut syndrome. NICE says that children with Lennox-Gastaut syndrome should have a specialist children’s doctor with expertise in epilepsy involved in their care. These specialists are called paediatric neurologists.


Your child will often need to take a number of different epilepsy medicines to help control their seizures. Your doctor will usually try a drug called sodium valproate first.

Sodium valproate can harm an unborn baby if taken during pregnancy. It’s still thought to be the best treatment choice available for Lennox-Gastaut syndrome. Doctors should explain the risks and benefits of taking sodium valproate to families and those who are able to become pregnant, as soon as they are old enough.

Sodium valproate is unlikely to completely control and stop your child’s seizures. Your doctor may also prescribe another medicine called lamotrigine either on its own, or as well as sodium valproate. If treatment with sodium valproate and lamotrigine still isn’t enough, other medicines your child’s doctor might suggest include:

  • Cannabidiol with clobazam – only if your child is over 2 years old, and they can be monitored every 6 months to check that it’s working well
  • Clobazam
  • Rufinamide
  • Topiramate

Other treatment options

If your child is still having seizures after trying the treatments listed above, their doctor may suggest trying the ketogenic diet alongside your child’s medicine.

If no other treatment options for Lennox-Gastaut syndrome are working, they may also try a medicine called felbamate.

If your child’s epilepsy doesn’t respond well to the different epilepsy medicines or the ketogenic diet, their doctor should refer them for assessment in a specialist centre. This will be to discuss whether epilepsy brain surgery might be an option for your child. If surgery isn’t a suitable option, the specialist might suggest a treatment called vagus nerve stimulation (VNS) instead.

Emergency treatment for prolonged or repeated seizures

Children with Lennox-Gastaut syndrome are very likely to have seizures that last a long time or happen often. This includes convulsive and non-convulsive status epilepticus which is a medical emergency. Your child’s doctor will discuss a ‘rescue’ or emergency care plan with you to treat repeated seizures, or seizures that last a long time.


A very small number of children with Lennox-Gastaut syndrome will outgrow their seizures by their mid to late teenage years. Most children and young people will continue to have seizures into adult life. However, they will often have fewer seizures as they get older. Most people with Lennox-Gastaut syndrome will continue to need support and care throughout their life, and aren’t able to live independently.

A number of health professionals may be involved in your child’s care. This will usually include a clinical psychologist or child psychiatrist who can help with behavioural problems. You may also see an occupational therapist who can advise on things you can do to limit accidents and injuries. This might include using helmets and wheelchairs, and adapting your living environment. Your child is likely to need additional support at school, and may benefit from a specialist school that can meet their needs.

Caring for a child who has Lennox-Gastaut syndrome can bring up lots of challenges. We have support available through our Helpline, Befriending service and Talk and Support groups. You can also get information, advice and support from the groups listed below.


Lennox-Gastaut Foundation

This organisation is based in America. As well as information, it offers a support group for families across the UK. The group is hosted on Facebook and is private to families who live with LGS.

Tuberous Sclerosis Association

Advice and support for families affected by tuberous sclerosis.

Support line: 0808 801 0700
Email: support@tuberous-sclerosis.org

Contact – for families with disabled children

Freephone helpline: 0808 808 3555
Email: helpline@contact.org.uk


This information has been produced under the terms of the PIF TICK. The PIF TICK is the UK-wide Quality Mark for Health Information. Please contact website@epilepsy.org.uk if you would like a reference list for this information.
Published: September 2022
Last modified: October 2023
To be reviewed: July 2026
Tracking: A032.06 (previously S007)
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