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Lennox-Gastout Syndrome (LGS)
Sunday, 31 August 2003
Monday, 12 January 2004


Lennox-Gastaut Syndrome (LGS) is a childhood epilepsy syndrome that is characterized by multiple types of seizures, mental retardation, and characteristic electroencephalogram (EEG) patterns. Children with LGS often have multiple seizure types including atypical absence (staring spells without conscious control), tonic (generalized stiffening of muscles), atonic (sudden loss of muscle tone causing collapse), and myoclonic (sudden and rhythmic muscle jerking).  Status epilepticus also frequently occurs.


Children with LGS typically develop seizures between 1 and 8 years of age, with a peak incidence between 3 and 5 years of age. Overall, LGS accounts for about 5% of childhood epilepsy. Males are affected more frequently than females.

Signs and Symptoms

Children with LGS may experience a variety of different seizure types. Tonic seizures, characterized by muscle stiffening, are common during sleep or upon awakening. Other seizure types usually occur during periods of wakefulness. Some children are developmentally normal when seizures first develop, although the majority are delayed.   Most children lose developmental skills in association with uncontrolled seizures.  Atonic seizures or "drop attacks" may also lead to injuries, commonly involving the face and head.

Possible Causes

Approximately ¾ of patients with LGS have an underlying neurologic cause and are referred to as "symptomatic" LGS.  The cause is usually a widespread brain injury such as damage secondary to prematurity, lack of oxygen during birth, severe infections of the nervous system, or genetic diseases such as tuberous sclerosis or metabolic disorders. How these injuries lead to severe and intractable seizures is not completely understood, but it may be that early brain injury leads to abnormal brain connections and neuron communication.

In approximately 25% of cases LGS symptoms appear without a previous history of a neurological disorder; these cases are called "cryptogenic." Approximately 25-50% of patients have infantile spasms prior to developing LGS.


In general, physicians diagnose LGS in patients who demonstrate multiple characteristic seizure types, developmental delay, and a specific finding on the EEG referred to as slow spike and wave.  Magnetic resonance imaging (MRI) is commonly used to look for an underlying cause. EEG, which measures the electrical activity of the brain, is used to record both awake and sleep periods to assist in confirming the suspected diagnosis of LGS.


LGS is difficult to treat and often does not respond to the usual anti-seizure medications, even when used in combination.  However, anti seizure medications usually decrease the frequency and severity of seizures and most patients benefit from treatment. Other treatment options include the ketogenic diet and vagus nerve stimulators.

The ketogenic diet (KD) is a high fat, low carbohydrate diet that mimics the effects of starvation and causes the body to produce chemicals called ketones in patients consuming it.     Several studies have shown a seizure reduction of > 50% in over half of the patients on the diet.   Although an area of continuing active research, the mechanisms by which the KD produces its anti seizure effects are unknown.  The ketogenic diet may be particularly helpful in patients with LGS. 

Vagus nerve stimulation (VNS) is a type of treatment in which short bursts of electrical energy are directed into the brain via the vagus nerve, a large nerve located in the neck. This device electrically stimulates the vagus nerve every few minutes and has been shown to improve seizure control in patients with uncontrolled seizures. The device may take up to a year to show maximum benefit. This device requires an operation for insertion as well as for removal.

Another surgical option is a corpus callostomy, a surgical procedure that partially disconnects the cerebral hemispheres.  This procedure can be effective in decreasing the frequency of atonic seizures or "drop attacks".


The prognosis for seizure control and mental development is poor. Daily seizures occur in most patients and persist into adulthood, but are usually less frequent than in childhood. Factors that predict a poor prognosis include brain malformation, onset before 3 years of age, prior infantile spasms, tonic seizures that persist while on anti-seizure medication, and severe mental retardation.

Connect with other parents

In the spirit of community and support, Madisons Foundation offers the unique service of connecting parents of children with rare diseases. If you would like to be connected to other parents of children with this disease, please fill out this brief form.


Epilepsy Foundation of America

A very complete Website with information about the syndrome as well as support networks and ongoing research.

Epilepsy Foundation of Australia

Website with a comprehensive list of international websites related to epilepsy and therapy.

National Institute of Neurological Disorders and Stroke

Summary of LGS with links to other sites, publications, and ongoing research.

Google Search for Lennox-Gastout Syndrome (LGS)

References and Sources

Nelson's Textbook of Pediatrics

Goetz: Textbook of Clinical Neurology, 1st ed.

If you would like to be connected to parents of children with this disease, please visit and click on Connecting Parents in the Information and Support section.

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