Eighteen children with medically refractory seizures, language deterioration, incoordination, and regression in behavior and intellect, and an EEG showing electrical status epilepticus during sleep (ESES), are reported from Beijing Medical University, and the University of Hong Kong, Republic of China. Age at seizure onset ranged from 7 months to 9 years, and ESES was diagnosed at 8.5 +/- 4.3 years (range = 3-21 yrs) after onset of seizures. Development of ESES signaled the appearance of neuropsychological, language, and behavioral deterioration. Underlying epileptic syndromes included Lennox-Gastaut (4), Landau-Kleffner (3), benign rolandic epilepsy variant (5), and epileptiform autistic regression in 3, 1 having Rett syndrome. Treatment with oral or intravenous clonazepam resulted in improvement in clinical and EEG manifestations, especially when treated within 2 years of seizure onset. Valproic acid was also effective in one half the patients, while carbamazepine, phenytoin, and phenobarbital were without benefit. Improvements in speech and cognitive function were correlated with suppression of ESES. 
COMMENT. The EEG phenomenon of electrical status epilepticus during sleep (ESES) in childhood may be associated with epileptic syndromes of various etiologies and outcomes. Benign rolandic epilepsy and Lennox-Gastaut syndromes represent the benign and malignant ends of the spectrum. The authors emphasize the importance of sleep EEG monitoring in children with an early onset of epilepsy associated with language, behavioral or psychological deterioration. Early treatment with oral benzodiazepines, especially clonazepam or clobazam, may reverse both the EEG and cognitive, language, and behavioral regression. The well known tendency to development of tolerance with use of benzodiazepines was considered unusual in the treatment of ESES in this study. Seizures and the ESES may be exacerbated by carbamazepine.