Before 1986, the spectrum of childhood epilepsies, including Lennox-Gastaut syndrome (LGS) and Doose syndrome (DS), known collectively as "epilepsia myoclonica astatica," was believed to represent a single disease. More recently, some investigators have considered these syndromes to be parts of a continuum. To clarify these theories, neurobiologic factors of the syndromes were studied to determine which qualities were shared and which were unique.
A retrospective (1975-1985), community-based (Helsinki metropolitan area and the province of Uusimaa) study was designed to seek children with features of LGS and DS. It was assumed that recall bias and the selection of documented history would be similar throughout the group. Ranks of increasing pathology were assigned to different seizure types, EEG results, and drug treatments. A similar procedure was applied to epidemiologic data. Spearman rank-order correlations were calculated to determine which features correlated with LGS and which correlated with less severe epilepsy.
The survey comprised 75 patients with broadly defined LGS. The annual incidence was 2 in 100,000 children aged 0 to 14 years. Prenatal or perinatal abnormalities did not correlate with severity of epilepsy. As compared with the relatively favorable ranks, the severe epilepsy ranks were more often associated with an early onset of epilepsy, an infectious disease at the onset, delayed development before epilepsy, abnormalities in neurologic or neuroradiologic examinations, and a deteriorating course of the condition.
Patients with LGS are more likely than patients with less severe epilepsy to have a younger age at onset of epilepsy, an infection or both, and a deteriorating course of the condition.