Researchers from the Epilepsy Unit, Helsinki University Central Hospital, Finland, prospectively evaluated the efficacy of antiepileptic drug treatment and long-term (5 years or longer) cognitive outcome in 32 children with ESESS. Epilepsies were atypical rolandic (AR) in 6 children, associated with Landau-Kleffner syndrome (LKS) in 9, and symptomatic in 17. Prospective treatment with valproate (VPA) combined with ethosuximide (ESM) in 17 children was effective in 3 (18%). Electrical status epilepticus during sleep was abolished in 16 patients. Pre-ESESS cognitive level was regained in a total of 10 (31%) children (4 with AR, 3 with LKS, and 3 with symptomatic epilepsy). The majority had permanent cognitive impairment. Younger age at ESESS diagnosis, lower IQ at diagnosis, and no response to drug treatment were predictive of an unfavorable cognitive outcome. Cognitive outcome depends on treatment response, on EEG and seizures, and on etiology. VPA combined with ESM was the most effective drug treatment. Eight of 16 nonresponders underwent epilepsy surgery. 
COMMENT. SES (or CSWS), the term used for the EEG phenomenon, is defined as spike and wave discharge in >85% of non-rapid eye movement (REM) sleep. The encephalopathy ESESS has a poor long-term outcome. Only one third cases regain a normal cognitive level. Control of seizures and abolition of SES are essential for cognitive recovery. Outcome is dependent on etiology. Patients with rolandic epilepsy and ESESS have the best prognosis, whereas those with ESESS caused by LKS or symptomatic epilepsy are usually impaired. Children with congenital hemiplegia, hydrocephalus, or thalamic injury with early onset epilepsy are at increased risk of ESESS, and should be carefully monitored. Surgery should be considered early in treatment of drug-resistant symptomatic ESESS.
In a series of 30 patients with ESES treated 1994-2007 in Tel Aviv, Israel, the syndrome evolved from benign partial epilepsy in 11 (37%), and another third had an underlying structural brain anomaly. The most effective AEDs were levetiracetam and clobazam, whereas valproate and ethosuximide were ineffective. Residual intellectual deficit correlated with duration of ESES.