Need for electroencephalogram video confirmation of atypical absence seizures in children with Lennox-Gastaut syndrome.

Children with childhood epileptic encephalopathy (Lennox-Gastaut syndrome) frequently have both multiple seizure types and nonepileptic stereotyped events that are difficult to differentiate. We hypothesize that electroencephalogram (EEG) video monitoring is essential for correct identification of atypical absence seizures in this population. All video/EEG monitoring records on patients with confirmed Lennox-Gastaut syndrome between September 1992 and December 1996 were reviewed for clinical events and EEG changes. A subset of patients with suspected atypical absence seizures during the video/EEG formed the cohort for analysis. Thirty-eight patients had 48 monitoring periods ranging from 1 to 4 days (mean, 2.2 days). Twenty-six monitoring periods captured suspected atypical absence seizures and formed the study cohort. Suspected atypical absence seizures were epileptic seizures in only 27% (7 of 26) of the study cohort. By contrast, parents reliably and correctly identified tonic, atonic, and tonic-clonic seizures in the study cohort. Reliable diagnosis and subsequent counting of atypical absence seizures in patients with Lennox-Gastaut syndrome cannot be made on the basis of observation and/or history alone. Future outpatient studies of investigational anticonvulsant medications for patients with Lennox-Gastaut syndrome should consider parental counts of atypical absence seizures unreliable. We recommend that video/EEG monitoring be done on all Lennox-Gastaut syndrome patients with suspected atypical absence seizures not controlled by medication.