Encephalopathy with hemi-status epilepticus during sleep or hemi-continuous spikes and waves during slow sleep syndrome: a study of 21 patients

Purpose: To retrospectively analyze the electroclinical features, etiology, treatment, and prognosis of 21 patients with encephalopathy with hemi-status epilepticus during sleep (ESES) or hemi-continuous spikes and waves during slow sleep (CSWSS) syndrome.

Methods: Charts of 21 patients with hemi-ESES/CSWSS syndrome followed between 1997 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 behavioral disturbances; (4) Hemi-continuous spike-and-wave discharges during slow sleep in more than 85% of non-REM sleep at onset and throughout the ESES/CSWSS period.

Results: Mean follow-up from onset of hemi-ESES/CSWSS was 8 years (range, 2-15 years). Idiopathic cases were not identified. Unilateral polymicrogyria was found in 11, shunted hydrocephalus in four, a porencephalic cyst associated with polymicrogyria in three, and a thalamic lesion in three children. All started with focal seizures with or without secondary generalization. During the hemi-ESES/CSWSS period, all children developed new types of seizure, such as negative and positive myoclonus, absences, motor deterioration, cognitive impairment, and behavioral disturbances. All AED responders returned to baseline cognitive development. Seven patients were refractory to AEDs.

Conclusion: Our study suggests that the hemi-ESES/CSWSS syndrome has electroclinical features compatible with an epileptic encephalopathy. The most commonly used treatments were clobazam, ethosuximide, and sulthiame, alone or in combination. In refractory cases, high-dose corticosteroids were administered. Although the number of patients in this study is too low to draw definite conclusions, we consider that in children with hemi-ESES/CSWSS secondary to a unilateral lesion, surgery should be considered.