Encephalopathy with status epilepticus during sleep or continuous spikes and waves during slow sleep syndrome: a multicenter, long-term follow-up study of 117 patients.

Purpose: To retrospectively analyze the electroclinical features, etiology, treatment and prognosis of 117 patients with encephalopathy with status epilepticus during sleep (ESES) or continuous spike and waves slow sleep (CSWSS) syndrome with a long-term follow-up.

Methods: Charts of 117 patients with ESES/CSWSS syndrome followed between 1990 and 2012 were analyzed. Inclusion criteria were: (1) focal seizures or apparently generalized seizures and focal EEG epileptiform discharges; (2) further occurrence of atypical absences, and myoclonic, atonic, and/or generalized seizures; (3) cognitive impairment and/or behavior disturbances; (4) continuous spike-and-wave discharges during slow sleep in more than 85% of non-REM sleep. Patients with spike-and-wave discharges in less than 85% of slow sleep were also analyzed.

Key Findings: 'Mean follow-up from onset of ESES/CSWSS was 13 years (range, 2-22 years) in the symptomatic/structural and non-idiopathic group consisting of 79 children and 10.5 years (range, 2-21 years) in the idiopathic group consisting of 38 children. The comparison of clinical findings and localization of paroxysmal EEG abnormalities (focal, multifocal, or generalized) at the different stages (before, during, and after ESES/CSWSS) and the percentage of spike-wave index during ESES/CSWSS between the symptomatic/structural and non-idiopathic and the idiopathic group was not statistically significant.

Significance: ESES/CSWSS syndrome is an epileptic encephalopathy with similar electroclinical findings in children with a >85% spike-wave index and those with a <85% spike-wave index. In this series of patients, the most commonly used treatments were clobazam, ethosuximide, sulthiame, alone or in combination. In refractory cases, high-dose steroids were administered. Among the AED responders, the idiopathic cases returned to normality and the structural cases returned to baseline cognitive development.