Abstracts

Rationale: Epilepsy with centro-temporal spikes (ECTS) in children may sometimes be complicated by an epileptic encephalopathy (EE) with continuous spike-and-wave during sleep (CSWS)¹. This epileptic syndrome associates severe global or task-specific cognitive regression with almost continuous and diffuse interictal epileptiform discharges (IED) during slow-wave sleep. Diagnosis of CSWS is of utmost importance as normalization of sleep EEG with anti-epileptic drugs, particularly corticosteroids, results in considerable cognitive improvements². CSWS diagnosis is typically based on a 24 hours or drug-induced sleep EEG. On the contrary of wake EEG, sleep EEG is not routinely performed in ECTS patients and is not easily and rapidly accessible.The goal of this study is therefore to determine wake EEG criteria that are predictive of CSWS occurrence in sleep EEG in order to rapidly identify which patients with a diagnosis of ECTS will benefit from sleep EEG.  Methods: Thirty patients were included in this retrospective case-control study based on the analysis of wake EEG of patients with typical ECTS (15 patients) and ECTS complicated by CSWS (15 patients). EEG were anonymized and scored by 4 independent readers (1 Senior > 15 years of experience, 2 mediums-2 years of experience, 1 junior-6 months of experience). The following qualitative and quantitative EEG criteria were analyzed: slow wave index (SLWI), spike wave index (SWI), spike wave frequency (SWF), cluster of spike wave (CSW), secondary generalization (SG) and EEG grade (between 0 et 4) according to Aeby-Van Bogaert classification³. Sensibility and specificity of each criteria was assessed with receiver operating characteristic (ROC) curves and their reproducibility with a kappa test. Results: Each EEG criteria was significantly different between the two groups (p<0.05) except the SLWI for reader n° 3 (medium). The two most significant EEG criteria (p<0.0001 for the 4 readers) were the presence of a grade of 3 or higher (sensibility 99%, specificity 74%) and the presence of SG (sensibility 75%, specificity 90%) with an excellent kappa (respectively 0,85 et 0,86).  Conclusions: This study demonstrates that a grade > or = to 3 and the presence of SG for IEDs on a wake EEG can predict with good sensibility, specificity and reliability across readers, which patients with ECTS are at risk of presenting CSWS on sleep EEG.References1. Van Bogaert P. Epileptic encephalopathy with continuous spike-waves during slow-wave sleep including Landau-Kleffner syndrome. Handb Clin Neurol. 2013;111:635–640.2. Buzatu M, Bulteau C, Altuzarra C, et al. Corticosteroids as treatment of epileptic syndromes with continuous spike-waves during slow-wave sleep. Epilepsia. 2009;50(Suppl 7):68–72.3. Aeby A, Poznanski N, Verheulpen D, et al. Levetiracetam efficacy in epileptic syndromes with continuous spikes and waves during slow sleep: experience in 12 cases. Epilepsia. 2005;46:1937–1942. Funding: No funding was received in support of this abstract