Abstracts

Rationale: Continuous EEG (cEEG) monitoring leads to the diagnosis of non-convulsive seizures and/or status epilepticus (NCS/NCSE) in 10-45% patients, depending on etiology and setting. This has led to a rapid increase in its utilization. Therefore, it is foreseeable that some patients may undergo cEEG monitoring more than once during a single hospital stay. However, the prevalence and utility of a repeat cEEG monitoring has not yet been studied. The aim of current study is to fill this knowledge gap. Methods: After IRB approval, our prospectively maintained cEEG database was searched from 01/01/2015 to 12/31/2015 to identify patients = 18 years of age who underwent a repeat cEEG monitoring within 2 to 30 days of index cEEG session. Patients with repeat cEEG in this period due to rehospitalization were excluded. The indications for cEEG were divided into unexplained altered mental status (uAMS) or seizure like episodes (SLE). Any changes in etiology, marked as “new etiology” between the two cEEGs was identified. Primary outcome was electrographic seizures on repeat cEEG and secondary outcome was increased epileptogenicity, defined as new epileptiform activity [regional/lateralized rhythmic delta activity (LRDA)/sharp waves, lateralized periodic discharges (LPD) etc.] compared to index cEEG. Statistical tools including chi square and t-test were used as required. Results: A total of 213 patients had repeat cEEG during same hospitalization, accounting for 8.6% of all unique patients monitored during 1 year study period. The mean age of study population was 60.5 ± 15 years and included 112 (52.6%) females. A total of 49 (23%) patients had history of epilepsy. Primary etiology was structural in 139 (65.3%) [acute 101 (72.7%), remote 8 (5.8%), progressive 29 (20.9%)] patients and non-structural in the rest. Electrographic seizures were noted in 35 (16.4%) patients on index cEEG. Median interval between two cEEG sessions was 5 (range 2-29) days. The reason for repeat cEEG was uAMS in 132 (62%) patients, SLE in 67 (31.5%) and miscellaneous in 14 [6.6%; including AED transition in 10 and vasospasm monitoring in 2 patients). Electrographic seizures were noted in 17 (8%) patients on repeat cEEG. They were more likely in patients with history of epilepsy, patients who had SLE prior to repeat cEEG and new etiology between repeat monitoring (Table 1). There was also a significantly longer time gap between two cEEG session in patient found to have seizures on repeat cEEG (p = 0.03). Increased epileptogenicity was noted on repeat cEEG in 33 (15.5%) patients, marked by first time findings of seizure in 11 (4.7%), sharp waves in 12 (5.6%), LPDs in 9 (4.2%) and LRDA in 1 patient. Conclusions: A sizeable patient population was noted to undergo repeat cEEG during single hospitalization at our institution. With 8% of patients found to have electrographic seizures, two-thirds of which were new patients, the practice of repeat cEEG may have significant clinical impact. This preliminary analysis suggests that certain patients, as summarized above, may be more likely to have seizure on repeat cEEG. Larger, multi-center studies are needed to expand on these initial findings. Funding: None