Lennox-Gastaut Syndrome (LGS)

Lennox-Gastaut Syndrome (LGS) is one of the more severe forms of epilepsy. It usually develops between one and eight years of age and is characterised by several seizure types and development delay. Seizures are generally difficult to control due to their resistance to anti-epileptic drugs.

What causes LGS?

Often no specific cause identifiable; however some of the known causes include:

  • Brain injury due to problems associated with pregnancy and birth including prematurity, asphyxia (lack of oxygen) and/or low birth weight.
  • Severe brain infections including encephalitis, meningitis, toxoplasmosis and rubella.
  • Genetic brain diseases, such as tuberous sclerosis, and inherited metabolic brain diseases.
  • Developmental malformations of the brain.

In many instances LGS is a sequel to infantile spasms which are sudden spasms or bending of the body, either at the trunk or neck. These usually commence at between three and eight months and may develop into the mixed seizure pattern, which characterises LGS, at two to three years.


There is also a number of rare childhood diseases which may lead to LGS.

How common is LGS?

It is estimated that LGS occurs in between 3 to 11 per cent of childhood epilepsies with slightly more males than females affected. The average age of onset is three years.

How is LGS diagnosed?

LGS is diagnosed by some or all of the following:

  • The presence of a mixed seizure pattern.
  • Some degree of developmental delay or intellectual disability.
  • A typical electromencephalogram (EEG) pattern of slow spike-and-wave discharges may be present.

What are the symptoms of LGS?


Seizures are always of several types and a child may experience some or all of these types. The most common seizure types associated with LGS are tonic, atonic and atypical absence seizures. Periods of frequent seizures may be interspersed with periods of relative freedom from seizures. (Refer to the common seizures types table for more information).


Most children with LGS experience some degree of impaired intellectual functioning or information processing. In approximately 65 per cent of children with LGS, intellectual disability is evident, either previous to or at the time of diagnosis. In other children with LGS, intellectual disability becomes apparent within a year or two of the seizures beginning.


These include poor social skills and attention seeking behaviour; and have at least four possible causes:

  • The underlying condition causing the epilepsy.
  • The effects of medication.
  • The electrical disturbance in the brain in uncontrolled epilepsy.
  • Difficulties with interpreting information and understanding the world as others do.

Name Symptoms Duration
Tonic General stiffening of muscles
No jerking movements
May be limited to a brief increase of muscle tone in the neck and arms
Stiffening of the trunk and legs can lead to sudden falls
Commonly occur during sleep Several seconds to a minute
Atonic Sudden loss of muscle tone causing limpness and collapse to the ground
May result in injury
May involve head-nodding or sagging at the knees One to four seconds
A typical Absence Briefperiod of immobility with a stare
Responsiveness decreased but may not be completely abolished
Different EEG pattern from typical absence seizures
Onset less abrupt and recovery more gradual than typical seizures Five to 30 seconds

How is LGS managed?


Anti-epileptic drugs (AEDs) are usually the best treatment for seizures although complete seizure control is rarely achieved. LGS often requires frequent changes in dose and type of medication, with some medications losing their initial effectiveness. Unlike other childhood epilepsies, the simultaneous use of more than one type of medication is often necessary. The drugs most commonly prescribed for LGS are listed in the table below. There are also a number of new AEDs, currently being trialled in Australia and overseas, which appear to be achieving good results with LGS.

Common AEDs prescribed for LGS
Trade Name Generic Name Possible Side Effects
Epilim Sodium Valproate Diarrhoea, abdominal pain, nausea, vomiting, weight gain
Rivotril Clonazepam Aggression, depression, drowsiness, sedation, ataxia, (poor Co-ordination); drooling
Frisium Clobazam Drowsiness; weight gain
Zarontin Ethosuximide Behavioural disturbances; nausea, drowsiness; decreased appetite; abdominal pain; unsteadiness, hiccups, headaches, rashes


A ketogenic diet is a special diet which has been clinically effective in reducing seizures. This type of diet was commonly used before the availability of modern anti-epileptic drugs but is rarely used today. It is very high in fat, often unpalatable and requires strict compliance.


In addition, the ketogenic diet elevates blood cholesterol levels markedly and is expensive to implement. It is not a long–term position.

Attention To Seizure Precipitants

It is recognised that the frequency of seizures may be associated with the child’s level of alertness. The child who is overexcited for example, or lacks sufficient stimulation, may experience more seizures.


A stimulating but stable environment can therefore be important in reducing the number of daily seizures. This may include a strict routine of regular meals, sleep and medication. Illness may also trigger seizures. For example; often seizure activity may increase just before the onset of high body temperature and fever. Vomiting and diarrhoea can also affect the body’s ability to absorb medication.

Status Epilepticus

Status Epilepticus (“status”) occurs in about 50 per cent of people with LGS and is the term used to describe prolonged seizures without regaining consciousness between attacks. Status can occur with any type of seizure and is categorised as either convulsive or non-convulsive. Status can last from hours to days, in the case of non-convulsive status, even weeks or months. Factors which may lead to status include sudden withdrawal from medication, illness, fever and infections.


Status in children with LGS is most often non–convulsive. It is characterised by severe confusion, apathy or a “flat” mood, stupor or, at worst apparent dementia.


Inconspicuous muscle spasms and greatly impaired balance and co–ordination are usually evident. Conclusive status may ultimately lead to brain damage and death unless stopped quickly, usually with the administration of rectal valium. Some parents and carers learn to administer rectal valium at home. This option would need to be discussed with your doctor.

What does the future hold for a child with LGS?

To date, little research has been conducted into the prognosis of children with LGS. It is clear, however, that prognosis varies from child to child. Generally, this syndrome is permanent. A few years after diagnosis, the epilepsy, which was so difficult to control, may become less of an issue but impaired intellectual functioning and behavioural problems frequently persist. Complete recovery, with freedom of seizures and normal development, is very unusual for the child with LGS.

Practical suggestions

(To Help Carers Support The Child With LGS)

  • Consider using respite care schemes which are provided by local councils and other organisations. These schemes offer the opportunity to have a professional carer visit your home to look after the child; or place the child with another family or residential centre. Respite care can be organised either on a regular or occasional basis.
  • Keep a diary which details the child’s seizures, seizure precipitants and any side effects of current medications. This can be useful when reporting to doctors and in identifying seizure patterns and medication responses.
  • Use an intercom in the child’s bedroom to monitor any changes in their condition.
  • On outings, consider using a child–stroller for school age children going through a phase of frequent seizures.
  • Question your doctor about all aspects of the child’s treatment, including medications and their side effects, to ensure that you are sufficiently informed to confidently co–ordinate the day-to-day management of the condition.
  • If you have any unanswered questions about medications, contact your local pharmacist or the Drug Information Centre. However, do not alter your child’s medication schedule without consulting your doctor. Consider using a hand–held harness to help prevent falls and a helmet to protect the face and head.
  • Lower the temperature on the household’s hot water unit or install a low temperature hot water service to prevent scalds and burns.
  • Buy a dosette box and tablet cutter from your local pharmacy to assist in preparing and administering medication.
  • The Independent Living Centre offers information and a range of aids which may assist in supporting the child with LGS.

Published by the Epilepsy Foundation of Victoria Inc (Updated May 99)


Medical consultant: Dr Ian Hopkins (courtesy Royal Children’s Hospital, Melbourne)