Lennox-Gastaut syndrome (LGS) is a severe form of epilepsy that typically becomes apparent during infancy or early childhood. Affected children experience several different types of seizures most commonly atonic, tonic and atypical absence seizures. Children with Lennox-Gastaut syndrome may also develop cognitive dysfunction, delays in reaching developmental milestones and behavioral problems. Lennox-Gastaut syndrome can be caused by a variety of underlying conditions, but in some cases no cause can be identified. Lennox-Gastaut syndrome can be difficult to treat because it is resistant (refractory) to many kinds of antiseizure medications. Research is ongoing to identify and assess new therapies for Lennox-Gastaut syndrome.
There is no consensus in the medical literature on the exact definition of Lennox-Gastaut syndrome. Generally, three findings are necessary for the diagnosis: multiple generalized seizure types; a slow spike-and-wave pattern (less than 2.5 Hz) on EEG; and cognitive dysfunction. The International League Against Epilepsy (ILAE) Task Force most recently classified the disorder as an epileptic encephalopathy. Epileptic encephalopathies are a group of disorders in which seizure activity leads to progressive cognitive dysfunction.