Definition and natural history of Lennox-Gastaut syndrome.

Lennox-Gastaut syndrome (LGS) is a rare epileptic encephalopathy with a peak age of onset of 3-5 years of age. Reported prevalence rates for LGS vary widely from 1-10% of all childhood epilepsies. Incidence rates are much lower. LGS is characterized by intractable, multiple, generalized seizure types and an interictal electroencephalogram showing bursts of slow spike-and-wave, paroxysmal bursts of generalized polyspikes, and a slow background. All patients have tonic seizures during sleep that may be subtle, and nearly all have treatment-resistant, lifelong epilepsy. Cognitive stagnation and behavioral problems are seen in almost all patients and lead to a life of dependency. The differential diagnosis includes other symptomatic generalized epilepsies and pseudo-Lennox syndrome. Misdiagnosis is common. Children and adults with LGS have an enormous impact on their families, and efforts to improve the quality of life for these patients are complex. Wiley Periodicals, Inc.