Lennox-Gastaut Syndrome was defined by Gastaut (France) in 1966 as a very severe variety of childhood epilepsy, with characteristic features. Dr. Lennox in Boston described features of the EEG in this condition.

Characteristics of Lennox-Gastaut Syndrome:

1. Multiple seizure types, including tonic (usually a requisite), atonic or drop attacks, atypical absence and myoclonic and generalized tonic-clonic seizures starting in childhood.
2. A characteristic EEG pattern (slow spike-waves) seen between seizures.
3. Cognitive impairment or developmental delay that is frequently progressive.

Before or at onset, 20 to 30% of children with LGS appear to have no neurologic deficit or development issues. These problems almost always appear during the course of LGS.

Factors known to be associated with intellectual or development disability are LGS with a defined cause, a prior history of infantile spasms, onset of symptoms before age 1 to 2 years, and high seizure frequency. Intellectual deterioration is typically seen over time, and estimates in adults reveal 95% to 100% with cognitive impairment. Some individuals do not show obvious intellectual impairment, especially if the seizures come on later in childhood and are not too frequent or severe.

In addition to the slowing or arrest of development, some children develop changes in behavior, mood or personality. As older children or adolescents, irritability, aggressiveness or social isolation may occur. It is important to be aware of these other possible symptoms in order to assist the child and family with care in these areas. The EEG abnormalities associated with LGS may account for some of the changes seen over time in intellectual function and behavior.

Author: James Wheless, M.D.
Topic Editor: Robert Fisher, M.D., Ph.D. ; Joseph Sirven, MD
Last Reviewed: 4/1/2012