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At a glance

It is a severe childhood onset form of intractable epilepsy that begins between the second and sixth year of life. Classically, it is defined by a triad of clinical signs consisting of severe learning disabilities, frequent seizure activities, and an EEG recording characterized by less than 2.5 Hz slow pike wave recording. Daily multiple seizures are typical and the most frequent type of seizures is myotonic and occurring 90% during the night. The second most frequent presentation is myoclonic seizures triggered when the patient is physically exhausted. It is associated with a poor prognosis in childhood. Five percent of patients die within 10 years from the onset of the disease.

Synonym

Childhood Epileptic Encephalopathy Disease.

History

First described in 1770 by Tissot, who reported an 11-year-old boy with frequent drop attacks, myoclonus, and progressive functional impairment.

Incidence

It is estimated to occur in 0.1 to 0.28 per 100,000 and is believed to account for 1 to 4% of all cases of childhood epilepsy. The annual incidence in children is estimated at 2:100,000. Onset is usually between 2 and 7 years with a peak between 3 and 5 years. The prevalence has a male predominance. There is no racial predominance.

Genetic inheritance

Commonly, there is a history of epilepsy in the family of children with Lennox-Gastaut Syndrome, but no familial case of this syndrome has been reported.

Pathophysiology

Unknown even though many favoring factors have been suggested, such as brain injury at birth, brain infections genetic brain diseases (eg, tuberous sclerosis and inherited metabolic brain diseases), brain malformations, and West Syndrome. Excessive permeability in the excitatory interhemispheric pathways in the frontal areas might play a role. Immunogenetic mechanisms may be involved in triggering or maintaining some cases of Lennox-Gastaut Syndrome. One study found a strong association between Lennox-Gastaut Syndrome and the human lymphocyte antigen class I antigen B7, but a second study did not.

Diagnosis

Clinical presentation and characteristic electroencephalographic (EEG) pattern. The EEG shows spikes and slow frequency waves of 1.5 to 2.5 Hz. The background rhythm is slow with multifocal spikes. The maximal voltage area is usually anterior.

Clinical aspects

Peak age for onset is between 3 and 5 years (extremes: 1-10 years). The syndrome consists of the triad of intractable seizures (tonic seizures, drop attacks, atypical absences) mental retardation, and characteristic EEG. Affected patients have a large variety of seizures that occur at any time (day and night). Consciousness may be only partially affected, and patients may remain rather active but “distant,” with loss of tone of muscles of the face and neck resulting in impaired balance or abnormal posture. Severe cases of status epilepticus may develop. Lennox-Gastaut Syndrome ...

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