Spike-Wave Index Assessment and Electro-Clinical Correlation in Patients with Encephalopathy Associated with Epileptic State During Slow Sleep (ESES / CSWS); Single-Center Experience

Purpose: This study aimed to describe the electroclinical spectrum and neurocognitive outcome in children with epileptic encephalopathy with status epilepticus during sleep (ESES) according to the EEG patterns.

Methods: Records of 48 (19 males, 29 females) patients with ESES/CSWS syndrome were retrospectively evaluated for data on sleep and awake EEGs, psychometric tests, and brain MRI. Patients with a spike-wave index (SWI) of at least 50 % in the NREM sleep EEG were included in the study. Electrophysiologic findings were separated into two groups based on SWI: SWI>85-100 % (typical ESES) and SWI < 85 % (atypical ESES). The neurocognitive prognosis was also evaluated in two groups; favorable and unfavorable.

Results: The median age at the onset of ESES was 6 years and 5 months and ranged from 3 to 13 years. The median duration of follow-up after the ESES diagnosis was 57 months (range 24-150 months). Etiology was evaluated in three groups: symptomatic/structural, idiopathic, and unknown (cryptogenic). Twenty-seven (56.25 %) patients had atypical ESES patterns and 21 patients (43.75 %) had typical ESES patterns. Twenty-eight patients (58.3 %) had cognitive deterioration. Long term neurocognitive outcome was unfavorable in half of the patients. Symptomatic/structural etiology was more common in patients with unfavorable (p < 0.001) outcomes. The median age at the diagnosis of ESES (p < 0.001) was significantly earlier in the patients with unfavorable neurocognitive outcomes. The longer duration of ESES(p < 0.001), and the longer time between the onset of epilepsy and ESES (p = 0.039) was significantly associated with unfavorable outcomes. We found that patients with typical ESES had a higher risk for poor neurocognitive outcomes than patients with atypical ESES (OR: 31.096 [1.565-617.696]).

Conclusion: The long-term outcome of ESES is exceedingly variable. An unfavorable neurocognitive outcome seems to be related to ESES with a long-duration and early-onset epileptic activity, SWI ≥ 85 %, and etiology.