Abstracts

Rationale: Slow-wave sleep plays an important role in memory consolidation and learning. Memory loss and learning difficulties are major problems in patients with Electrical Status Epilepticus in Sleep (ESES). Impaired slow-wave activity (SWA) may in part be responsible for neurocognitive problems in ESES patients. We investigated changes in Interictal epileptiform discharges (IEDs) and SWA in electroencephalograms (EEGs) of ESES patients, and compared findings with normal individuals. Methods: In this retrospective case-control study, 15 patients (aged 3-11 years) diagnosed with ESES (spike wave index of ?-50%) were included. We also evaluated 15 age- and sex-matched children with a normal EEG as controls. All patients in the study and control groups had at least one overnight EEG. Only the first overnight EEG recordings were chosen for analysis. Patients who had a history of corticosteroid use or who received benzodiazepines were excluded. Sleep stage scoring was performed according to standard criteria (American Academy of Sleep Medicine, 2015). SWA or Delta amplitude was measured as Delta Power (DP) using Fast Fourier Transform (FFT) analysis. Total spike numbers were assessed by both manual and semi-automatic counting algorithms. All measurements were performed during 20 minute epochs of sleep stage 3 during the first and the last NREM sleep cycles of the overnight recording. Mann-Whitney U test was used for independent samples, and Wilcoxon signed-rank test for dependent samples. Results: The study and control groups consisted of 9 males and 6 females each, with a median age of 7.1 years (IQR: 5.3-9.6 years) for cases and 6.9 years (IQR: 5.2-10 years) for controls. The control group did not have any IEDs, and demonstrated a normal physiological decrease in terms of DP between the first and the last NREM sleep cycle (median V; 21.7 to 6.8, p < 0.001). In the study group, there was no difference with respect to spike counts between first NREM and last NREM sleep by manual (median: 1531 vs 1475, n.s.) and semiautomatic spike counter as well (median: 1511 vs 1494, n.s.).In terms of DP, there was no difference in median DP comparing the first to the last NREM sleep cycle (25.7 vs 18.8V, n.s.). Comparing cases and controls, there was no difference between the median DP during the first NREM sleep cycles (median V; 25.7 vs 21.7, n.s.). DP of last NREM slow wave sleep cycles differed between both groups (median V; 18.8 vs 6.8). DPs and spike counts were not influenced by age and gender. Conclusions: We noted a lack of physiologic decrease of DP in slow wave sleep comparing first and last NREM sleep cycle in ESES patients. Lack of DP decrease may play a role in neurocognitive deterioration of ESES patients, and DP measurements may serve as a clinical biomarker. Further correlation with cognitive and clinical variables in larger patients are needed to validate results. Funding: No funding was received for this study.