Abstracts

Rationale: Continuous electroencephalographic (cEEG) monitoring is now routinely performed in critically ill patients. Several rhythmic and periodic patterns including lateralized rhythmic delta activity (LRDA) and lateralized periodic discharges (LPDs) have been identified as lying on the ictal-interictal continuum (IIC) between definite seizure activity and non-ictal brain irritability. (Hirsch LJ. J Clin Neurophysiol. 2004;21(5):332-340). LRDA has been associated with a high risk of acute (in-hospital) seizures ranging between 25-63% (Rodriguez Ruiz A. JAMA Neurol. 2017;74(2):181-188). Initial reports showed comparable clinical characteristics and risk of acute seizures between LRDA and LPDs (Gaspard N. JAMA Neurol. 2013;70(10):1288-1295). While LPDs are independently associated with poor outcomes, the acute and long-term outcomes in patients with LRDA are unknown. Given the similar acute seizure risk and clinical characteristics of the two discharge types, it is possible that the outcomes of patients with LRDA may be similar to those of patients with LPDs (Johnson. Clinical Neurophysiology Practice 2 (2017) 107-118). We performed a retrospective observational study centering on the comparison of patients with LRDA and patients with LPDs to answer these questions. Methods: This was a single center retrospective cohort reviewing critically-ill adult patients who underwent continuous electroencephalographic (cEEG) monitoring between December 2015 and December 2017. Patients were divided into 4 subgroups: LRDA-only, LPD-only, both LRDA/LPD and control (non-ictal slow activity). The primary outcomes were in-hospital mortality, acute electrographic seizures, development of epilepsy and functional outcomes assessed by mRS. Outcomes were assessed upon hospital discharge and follow up in neurology clinic. Results: Over a 2-year period, 197 patients were included in the cohort, 28 patients were in LRDA-only group, 76 in LPD-only group, 25 in LRDA/LPD and 68 in the control group. There were no significant differences among the four groups in age, gender, etiology or brain MRI findings. Patients in LPD-only and LRDA/LPD groups had higher percentage of a prior history of epilepsy (table 1). There were no significant differences in the neurological examination between LRDA-only and LPD-only groups. None of the patients in LRDA-only group died during their hospitalization, compared to 28% in LPD only group, 8 % LRDA/LPD group and 10% in the control group (table 2). Patients in LPD-only group had 2.75 higher odds of mortality (CI 1.0 -7.7, p 0.04) compared to LRDA-only group. Compared to the control group, the odds of having electrographic seizures was highest in patients with both patterns (24.5, 5.9 - 102, p<0.001), followed by LPD-only (12.3, 3.8 - 40.4, p<0.001) then LRDA-only (7.6, 1.8 - 33.1, p 0.007). Upon follow up in clinic, there was no significant difference within the cohort with regards to the development of epilepsy. Patients with LRDA-only had a trend towards a better functional outcome compared to controls (OR 3.4, CI 0.96-12, p 0.057). Conclusions: There were no acute in-hospital deaths in the LRDA-only group and those patients tended to have a better functional outcome compared to control group upon follow up (OR 3.4). The odds of developing acute in-hospital seizures was highest when both patterns were present together. While LRDA has been shown to carry a similar risk for developing seizures in the acute setting, the long-term outcomes for patients with LRDA appear to be rather different compared to patients with a similar clinical picture but a different type of discharge pattern on the IIC. Funding: No funding