Lennox-Gastaut syndrome is an epilepsy syndrome that causes different types of recurrent seizures (tonic, atonic and atypical absence) and intellectual disability. It is usually challenging to keep the seizures under control, although some newer treatments offer improved control.
What are the features of Lennox-Gastaut syndrome?
The first seizure usually happens when the child is between one and eight years old. Children with an identified cause for Lennox-Gastaut syndrome can present earlier than children with no obvious cause.
The three classic features of Lennox-Gastaut syndrome are:
- Frequent generalized seizures of different types, usually tonic (stiffening), atypical absence (staring), myoclonic (jerks) and atonic (loss of muscle tone). Tonic seizures are the defining seizure type of this syndrome. Frequently there are “drop” attacks or falls as a result of the atonic or myoclonic seizures and, rarely, tonic seizures.
- Diffuse slow spikes and waves on the EEG.
- Intellectual disabilities, which may not be obviously noted until later in the course of the syndrome.
Tonic seizures occur in between 74% and 90% of children with Lennox-Gastaut syndrome. The following types may be seen:
- The child’s head and body bend inward.
- The child’s upper arms and shoulders rise, their neck muscles stiffen, their mouth opens, their eyes roll upward and they briefly hold their breath.
- The child’s whole body is involved and they can fall suddenly.
The seizures usually happen when the child is falling asleep, but they can happen at any time of day. They may be triggered by noise, contact or movement.
About two-thirds of children with Lennox-Gastaut syndrome have atypical absence seizures. These are usually longer than typical absence seizures, starting gradually and usually leaving the child confused for a short time afterwards. The child may not lose awareness completely. They may also have some twitching around the eyes or mouth or their neck may stiffen. Their head and body may droop due to a loss of muscle tone.
Most people with Lennox-Gastaut syndrome will have at least one episode of non-convulsive status epilepticus. Absence status epilepticus is more common in children and may be difficult to recognize in children with severe developmental disability.
Most children with Lennox-Gastaut syndrome have some degree of intellectual disability, although it may not be recognizable until later. Developmental disability is more likely if the seizures begin before age three, the child has frequent seizures or repeated status epilepticus.
In young children with Lennox-Gastaut syndrome, achievement of developmental milestones may slow down or stop. If the syndrome develops later, cognitive impairment may not be as severe. Motor development is usually affected less than cognitive development.
Behavioural problems are common in children with Lennox-Gaustaut syndrome. These may include hyperactivity, emotional instability, aggressive or destructive behaviour and autistic features.
Children with Lennox-Gastaut syndrome may also have associated neurological problems, including cerebral palsy or visual and hearing impairment.
What causes Lennox-Gastaut syndrome?
Lennox-Gastaut syndrome may develop in a child with no previous problems, a child with an existing neurological problem, or a child with another form of epilepsy. About one-third of children with Lennox-Gastaut syndrome have a previous history of infantile spasms.
About 70% of cases of Lennox-Gastaut syndrome have an identified cause, while the rest have no obvious underlying cause. Children with an unidentified cause for Lennox-Gastaut syndrome are more likely to have a family history of epilepsy than children with a known cause for the syndrome. However, there is no evidence that the syndrome is inherited from parents.
Lennox-Gastaut syndrome can be caused by:
- genetic abnormalities
- brain injury at or around birth
- congenital brain malformations
- brain infections
How many children have Lennox-Gastaut syndrome?
Lennox-Gastaut syndrome is rare, but it is seen quite often in paediatric epilepsy clinics. Different studies have found different rates of Lennox-Gastaut syndrome in various populations. It is estimated that one child in 50,000 to 100,000 will develop Lennox-Gastaut syndrome. It seems to be slightly more common in boys than in girls.
How is Lennox-Gastaut syndrome diagnosed?
Lennox-Gastaut syndrome has features in common with several other conditions, including epilepsy with myoclonic-astatic seizures, continuous spike waves in slow sleep, infantile spasms and Angelman’s syndrome. To rule these out and make a diagnosis of Lennox-Gastaut syndrome, the health-care team will need to assess the seizures carefully and perform an EEG.
How is Lennox-Gastaut syndrome diagnosed?
Lennox-Gastaut syndrome has features in common with several other conditions, including epilepsy with myoclonic-astatic seizures, continuous spike waves in slow sleep, infantile spasms and Angelman’s syndrome. To rule these out and make a diagnosis of Lennox-Gastaut syndrome, the health-care team will need to assess the seizures carefully and perform an EEG.
Commonly used medications include sodium valproate, clobazam, topiramate, lamotrigine, levetiracetam and lacosamide. Rufinamide has been shown to be particularly useful for tonic seizures in Lennox-Gastaut syndrome. Newer medications which may be beneficial include cannabidiol (CBD), fenfluramine, soteclestat and cenobamate.
The ketogenic diet is often able to reduce seizures in children with Lennox-Gastaut syndrome and also may help to improve cognition and alertness.
Vagus nerve stimulation (VNS) may reduce seizures in some children. Deep brain stimulation (DBS) is also beneficial in some children with Lennox Gastaut syndrome to reduce or eliminate seizures.
A surgical procedure called corpus callosotomy may reduce or eliminate tonic or atonic seizures. In rare cases, there may be a focal abnormality in the brain which is causing the syndrome. For these patients, resective epilepsy surgery may lead to seizure freedom.
What is the outlook for a child with Lennox-Gastaut syndrome?
Lennox-Gastaut syndrome generally has a poor long-term outlook, but this depends on multiple factors. Complete seizure control is rare, and most children will have cognitive and behavioural problems. However, a few adults with this syndrome are able to live independently. At the end of one study that observed children with this syndrome for more than 12 years, 21% of the study participants were in regular school classes or jobs.
It is also important to understand that there are currently many newer treatments available. Health-care providers and researchers hope the long-term prognosis for children will improve with these newer treatments.
Factors that are associated with poor seizure control and developmental disability include:
- an identified cause for the syndrome
- early onset of seizures
- frequent seizures
- repeated episodes of status epilepticus