Abstracts

Rationale: Status epilepticus (SE) is associated with increased morbidity and mortality. Numerous prognostic factors have been identified for outcomes following status epilepticus, although the relationship between sleep architecture and outcomes following SE has not been investigated. Sleep disturbance is frequently seen in neurological diseases, and the relationship between epilepsy and sleep is particularly complex. Poor sleep can exacerbate seizures. Conversely, poorly controlled epilepsy and anti-epileptic drugs can alter sleep architecture. Indeed, impaired sleep architecture has been identified as a poor prognostic factor in other conductions including posttraumatic coma, intracranial hemorrhage, subarachnoid hemorrhage, cardiac arrest, acute encephalopathy and critically ill patients on mechanical ventilation. The aim of this study is to investigate the association between the presence of sleep architecture in patients with SE documented on continuous EEG (cEEG) and outcome as measured by 3- and 6-month mortality, survival time and duration of hospitalization.

Methods: This is a retrospective cohort study of all adult patients (18 years or older) undergoing cEEG at Kingston Health Sciences Centre, Ontario from 2015-2019 where electrographic status epilepticus was identified via EEG. Recordings were assessed for the presence of sleep architecture by epileptologists blinded to the patient’s outcome. This was defined as any combination of the features of N2, slow wave sleep or REM sleep seen in at least one 30-second epoch during the cEEG. Association between presence of sleep architecture and mortality (2-tailed Fisher’s exact test), total survival time (Kaplan Meier Survival Curve), as well as duration of hospitalization (2-tailed Mann Whitney U test) were analyzed.

Results: Over the study period, a total of 223 cEEG studies were completed of which 25 were adult patients with electrographic status epilepticus identified at some point during their cEEG. The mean cEEG duration was 2.23 ± 0.4 days. Patients with an absence of sleep architecture i.e., no sleep architecture was identified at any point, had increased mortality rate at 3- and 6-months, as all patients that survived 3 months also survived 6 months (P = 0.041 for both, 62% died with no sleep architecture, 17% died with sleep architecture; Figure 1A). Absence of sleep architecture was also associated with reduced total survival time (P = 0.021; Figure 1B) with an effect size of 1.20. There was no difference in hospitalization time (P = 0.57). Patients with an absence of sleep architecture were also more likely to be female (P = 0.03).

Conclusions: The presence of sleep architecture during a cEEG in patients with electrographic status epilepticus is associated with a lower mortality rate at 3- and 6-months, even if the period of sleep is as little as one epoch. This suggests that the presence of sleep architecture may reflect less severe brain dysfunction, or alternatively it may serve as a protective and repair mechanism during neurological insults.

Funding: Please list any funding that was received in support of this abstract.: None.