Epileptic encephalopathy with continuous spike-and-wave during sleep (CSWS) or the newly named Epileptic encephalopathy with spike-and-wave activation in sleep (EE-SWAS) is a syndrome in which epileptiform abnormalities are associated with the progressive impairment of cognitive functions. This study aimed to evaluate the neurocognitive executive functions of patients at later ages and determine the long-term prognosis of the condition, as well as the factors affecting this.

This is a hospital-based cross-sectional study of 17 patients with a diagnosis of CSWS, and a minimum age of 7.5 years. The Wechsler Intelligence Scale for Children-Fourth Edition (WISC-IV) was used for neurocognitive assessment. The use of immunotherapy (intravenous immunoglobulin and/or steroid for at least 6 months) at the time of initial diagnosis, baseline activity and spike wave index (SWI) of the last wake and sleep EEG, cranial MRI findings, active epileptic seizures since the last examination, and WISC-IV parameters were statistically compared. The results of patients with genetic etiology determined by the whole exome sequencing (WES) method are also reported.

A total of 17 patients were included in the study, with a mean age of 10.30 ± 3.15 years (range from 7.9 to 15.8 years). The mean full scale IQ score of the subjects was 61.41 ± 17.81 (range 39–91), classified as follows: 5.9% (n = 1), average; 23.5% (n = 4), low average; 5.9% (n = 1), very low; 35.3% (n = 6), extremely low (upper range); 29.4% (n = 5), extremely low (lower range) intelligence. Among the four domains of WISC-IV, the most affected index was the Working Memory Index (WMI). EEG parameters, cranial MRI findings and treatment with immunotherapy did not have a significant effect on neurocognitive outcomes. Thirteen patients (76%) were evaluated with WES for a genetic etiology. Pathogenic variants in 5 different genes (GRIN2A, SLC12A5, SCN1A, SCN8A, ADGRV1) associated with epilepsy were detected in 5/13 patients (38%).

These results indicated that neurocognition is highly affected in the long term in CSWS.