Background: Continuous video-EEG monitoring (cEEG) is a non-invasive tool to monitor the electrical brain function; it significantly improves seizure or status epilepticus detection in comatose patients in intensive care units (ICUs), which often do not show any specific clinical correlates. Recently, the European Society of Intensive Care Medicine published guidelines regarding the use of cEEG in the ICUs, recommending it for most patients with consciousness disorders. cEEG is time- and resource consuming as compared to routine spot EEG (rEEG, typically lasting 20-30 minutes). While centers in North America have been using it increasingly, most European - and all Swiss - hospitals still do not have enough resources to comply with these guidelines. In addition, while the superiority of cEEG to detect non-convulsive seizures or status epilepticus is proven, only one population-based study based on discharge diagnoses suggested that cEEG may improve patients' outcome. Current guidelines are thus based upon weak evidence and expert opinions. If cEEG leads to improved patients' care remains elusive. Moreover, little attention has been drawn towards quantitative EEG information beyond visual analysis, and the impact of such information on diagnosis, treatment, and outcome remains unclear.

Aim: To assess whether the use of cEEG in patients with consciousness impairment is related to an improvement of functional outcome, and to address the prognostic role of quantitative network EEG analyses in this cohort. Also, a cost analysis will be performed.

Methods: In this multicenter randomized controlled trial, adults with a Glasgow Coma Score (GCS) inferior or equal to 11 or a FOUR score inferior or equal to 12, regardless of etiologies, will be randomized 1:1 to cEEG for 30-48 hours or two rEEG within 48 hours, interpreted in a standardized way. Patients with detected seizures in the last 36h or status epilepticus in the last 96h will be excluded, as cEEG may represent the standard of care. Demographics, etiology, Charlson Comorbidity Index, GCS, diagnosis leading to EEG, mechanical ventilation, and subsequent use of rEEG/cEEG will be collected. The primary outcome will be mortality at 6 months. Secondary outcomes will blindly assess functional outcome at 4 weeks and 6 months, as well as seizure/status epilepticus detection rate and time to detection, infections rate, duration of ICU stay, change in patient management (antiepileptic drug introduced, increased, or stopped, brain imaging), and reimbursement. Analyses will compare the two interventional groups (intention to diagnose) regarding outcome, as a whole and stratified according to etiological subgroups, and other variables of interest. Additionally, lope cross correlation and horizontal visibility graphs will be applied to compute a weighted adjacency matrix consisting of all the pairwise interdependences between EEG signals, in order to characterize the integrative and segregative characteristics of the underlying functional brain networks and compare their relationship with the primary outcome. According to a previous estimate, patients with consciousness disorders undergoing cEEG have a 75% survival rate; while patients w/o cEEG 61%. Using a power of 0.8, an α error of 0.05, and a 2-side approach, 2x174 patients would be needed to detect this significant difference in survival.

Expected impact: This study will clarify if cEEG monitoring has a significant impact on functional outcome and define its cost effectiveness, and if network EEG analysis has a role in outcome prognostication. The results of this study will have a considerable potential to influence clinical practice regarding EEG and treatment of patients with altered levels of consciousness. If results will indicate that cEEG contributes to improve outcome, this will lead to the urgent need for implementation of cEEG with consecutive substantial impact on health care and resource allocation in larger Swiss and European hospitals.