Rationale:
Lateralized periodic discharges (LPDs) are an electroencephalographic (EEG) pattern that is often observed in critically ill patients with acute brain injuries, tumors, central nervous system infections, and inflammatory conditions. Studies show a significant risk of new-onset epilepsy (epileptogenesis) in patients with LPDs on continuous EEG (cEEG) monitoring.
1 However, the factors that predispose to epileptogenesis in this patient population remains unexplored. Our aim was to fill this knowledge gap, especially analyzing the role of LPD modifiers.
2
Methods:
This was a single center retrospective cohort study. We included adults, without epilepsy history, who had LPDs on cEEG monitoring during hospital admission to Cleveland Clinic from 2012 to 2015. We excluded subjects with newly diagnosed epilepsy during the admission (e.g., convulsive or electrographic seizure in a remote stroke patient). For all included subjects, we identified the time at which LPDs were first observed and reviewed the cEEG database to characterize LPDs based off American Clinical Neurophysiology Society (ACNS) rhythmic and periodic pattern (RPP) modifiers.
2 The outcome variable was clinical seizure after discharge (epilepsy development) as documented by a provider in the electronic medical record. We used a Cox regression model to analyze factors associated with epileptogenesis in patients with LPDs. The multivariable model included variables shown in Table 1. We used our model to calculate adjusted hazard ratios (aHR) for the development of epilepsy after adjusting for pertinent patient characteristics. We determined that there was no significant collinearity between variables. The Cox proportional hazards assumption was tested and confirmed.
Results:
We have included 105 patients (mean age 66.3±13.0 years, 55% women) so far. Etiology of LPDs was acute brain injuries in 77 (73%), metabolic/infectious encephalopathy in 13 (13%), progressive brain lesions in 5 (5%), and other etiologies in 12 (11%). Thirty-two (30%) patients developed epilepsy with a mean follow-up time of 47.2±39.2 months. We found a trend of association of LPD modifiers with epileptogenesis. These include LPD frequency of 1.5 Hz or greater [aHR 2.1, (95% CI 0.87-5.09)] and the presence of an LPD-plus pattern [aHR 2.67, (95% CI 0.95-7.47)].
Conclusions:
Our findings show that certain LPD features could be associated with an increased risk of epilepsy development. Of note, the LPDs features of 1.5 Hz or higher frequency and a plus pattern are also the most critical factors that increase risk of seizures during the acute period. This on-going project may lead to the discovery of more definitive EEG biomarkers of symptomatic epilepsy development.
References:
1. Punia V, Bena J, Krishnan B, Newey C, Hantus S. New onset epilepsy among patients with periodic discharges on continuous electroencephalographic monitoring. Epilepsia. 2018;59(8):1612-1620. doi:10.1111/epi.14509
2. Hirsch LJ, Fong MWK, Leitinger M, et al. American Clinical Neurophysiology Society's Standardized Critical Care EEG Terminology: 2021 Version. J Clin Neurophysiol. 2021;38(1):1-29. doi:10.1097/WNP.0000000000000806
Funding: None.