Abstracts

Rationale: Little data are available on predictors of cognitive long-term outcome of Encephalopathy with electrical status epilepticus in sleep syndrome (ESESS) which includes the clinical conditions associated with electrical status epilepticus (ESES), such as epilepsy with continuous spike waves during sleep (CSWS) and Landau-Kleffner syndrome (LKS). Methods: We included 32 children with ESESS and at least three years’ follow-up who were treated and followed up at our unit since 1991. Six children had idiopathic focal epilepsy, nine had LKS and 17 had symptomatic epilepsy. Before ESESS, 18 children were cognitively normal and only one was severely cognitively impaired. Neuropsychological follow-up for more than five years was available in 24 patients. Treatment response of abolition of ESES was documented with over-night video-EEG recordings Results: Abolition of ESES associated with change of medication was observed in 50% of the patients (idiopathic and LKS group 67%, symptomatic group 35%) at mean age of 7.8 years (range, 6.2 to 12.2 years). Eight treatment resistant children underwent epilepsy surgery. On latest follow-up at mean age of 11.9 years (range, 6.1 to 18.1 years), nine children (28%) had mild and 12 children (38%) had moderate or severe intellectual impairment. The idiopathic group had the most favourable outcome while no child of the symptomatic group regained pre-ESESS cognitive level. Medical treatment response was achieved in all 11 children with normal or nearly normal outcome. Early onset of ESESS was associated with poor outcome in the idiopathic and symptomatic group. Conclusions: Cognitive outcome in ESESS depends on the underlying etiology. Most children had permanent cognitive impairment of variable degree after ESESS. Medical treatment response leading to abolition of ESES is mandatory for favourable outcome.