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Synonyms: childhood epileptic encephalopathy
The Lennox-Gastaut syndrome is characterised by multiple types of epileptic seizures, a characteristic electroencephalogram (EEG) with generalised slow spike-and-wave discharges, psychomotor delay and behavioural disorders.The onset is usually before the age of eight, with a peak between the ages of three and five years. Late cases occurring in adolescence and early adulthood have rarely been reported.
- The most common seizure types are tonic-axial, atonic, and absence seizures; however, myoclonic, generalised tonic-clonic, and partial seizures may also occur.
- Seizures are often resistant to treatment.
- Lennox-Gastaut syndrome can be classified as either idiopathic (25% of the total) or symptomatic (75%). In idiopathic, normal psychomotor development occurs prior to the onset of symptoms and no neurological or neuro-radiological abnormalities are found.
- Symptomatic cases are due to diverse cerebral conditions, which are usually bilateral, diffuse, or multifocal, involving cerebral grey matter.
- Examples of underlying disorders responsible for symptomatic Lennox-Gastaut syndrome include encephalitis, meningitis, tuberous sclerosis, brain malformations, birth injury, frontal lobe lesions and trauma.
- There is a prevalence of about 2 per 10,000 in Europe
- The number of children affected is not known with certainty but it may account for about 3% of all childhood epilepsies
- Males are affected five times more often than females
Language is frequently affected, with both slowness in ideation and expression in addition to difficulties of motor dysfunction. Severe behavioural disorders (eg hyperactivity, aggressiveness and autistic tendencies) and personality disorders are nearly always present. There is also a tendency for psychosis to develop with time.
- 20% of all patients with Lennox-Gastaut syndrome have prior infantile spasms with hypsarrhythmia.
- The mean age of epilepsy onset is 2 years.
- Young children may show mood instability, personality disturbances, or slowing of psychomotor development.
- Older children experience personality problems, acute psychotic episodes, or chronic psychosis with aggressiveness, irritability, or social isolation.
- Mental deterioration leads to apathy and memory disorders.
- Physical examination can be important in helping to identify specific aetiologies although there are no pathognomonic physical findings.
- Epilepsy with mental retardation
- Infantile spasms
- Juvenile myoclonic epilepsy
- Myoclonic-astatic epilepsy
- Electroencephalogram (EEG):
- The EEG features are not pathognomonic of the disorder.
- Interictal EEG is characterised by a slow background that can be either constant or transient.
- The characteristic interictal EEG pattern is 1.5 to 2.5 Hz slow spike-wave activity, which is bilaterally synchronous, dominant over the frontocentral regions, and usually symmetrical.
- The characteristic diffuse slow spike-wave pattern gradually disappears with age and is replaced by focal epileptic discharges.
- MRI scan is important in order to search for an underlying aetiology.
- Positron emission tomography or single-photon emission computed tomography may be useful during evaluation for epilepsy surgery.
A ketogenic diet appears useful in a minority of patients. Potentially serious adverse effects include dehydration, metabolic acidosis when the diet is initiated, renal stones, cardiac abnormalities and an abnormal lipid profile.
- Anticonvulsants are the mainstay of therapy but the optimum treatment for Lennox-Gastaut syndrome remains uncertain. A combination of drugs is usually required.
- Rufinamide, lamotrigine and topiramate may be helpful as add-on therapy.
- Ethosuximide is also worth trying for atypical absences.
- Benzodiazepines can be effective in the remainder of seizure types but unfortunately the effect is often transient.
- Tonic seizures may persist and be more difficult to control over time, while myoclonic and atypical absences appear easier to control.
- Corpus callosotomy is effective in reducing drop attacks but typically is not helpful for other seizure types and is considered palliative rather than curative.
- Seizure freedom following corpus callosotomy is rare but can occur.
- Vagus nerve stimulation has been reported to reduce seizure frequency but the results are anecdotal.
- Injuries or death resulting from a seizure.
- Renal, cardiac, or metabolic complications resulting from a ketogenic diet.
- Long-term prognosis overall is unfavourable but variable.
- The epilepsy often improves but complete resolution of seizures is rare and the mental and psychiatric disorders tend to worsen with time.
- A minority of patients can eventually work normally, but many still have typical characteristics (mental retardation, treatment-resistant seizures) many years after the onset.
- A worse prognosis is associated with symptomatic Lennox-Gastaut syndrome, early onset of seizures, prior history of infantile spasms, higher frequency of seizures, or constant slow electroencephalogram (EEG) background activity.
Further reading & references
- Hancock EC, Cross HH; Treatment of Lennox-Gastaut syndrome. Cochrane Database Syst Rev. 2009 Jul 8;(3):CD003277.
- Glauser TA, Morita DA; Lennox-Gastaut Syndrome; eMedicine, December 2009.
- Markand ON; Lennox-Gastaut syndrome (childhood epileptic encephalopathy).; J Clin Neurophysiol. 2003 Nov-Dec;20(6):426-41.
- Epilepsy Society
- Arzimanoglou A, French J, Blume WT, et al; Lennox-Gastaut syndrome: a consensus approach on diagnosis, assessment, Lancet Neurol. 2009 Jan;8(1):82-93.
- British National Formulary; 58th Edition (September 2009) British Medical Association and Royal Pharmaceutical Society of Great Britain, London.
- Ohtsuka Y, Amano R, Mizukawa M, et al; Long-term prognosis of the Lennox-Gastaut syndrome.; Jpn J Psychiatry Neurol. 1990 Jun;44(2):257-64.
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Dr Colin Tidy
Dr Colin Tidy