Abstracts

Rationale: Prior literature has reported PLED frequencies of 0.1-1%, with stroke reported as the most commonly associated lesion (Orta et al., Arch Neurol 2009; 66: 985-991, and Pohlmann-Eden et al., J Clin Neurophysiol 1996; 13: 519-530). These studies, however, principally evaluated routine EEGs in mixed inpatient/outpatient populations. Neither the frequency of PLEDs nor their underlying etiologies have been systematically assessed in an inpatient population undergoing prolonged cEEG monitoring. Methods: Our archive of adult inpatients undergoing cEEG monitoring for non-elective indications between 2007 and 2011 was searched to identify all patients with PLEDs during this five-year period. Charts were reviewed for each patient with PLEDs, and multiple parameters pertaining to clinical demographics and cEEG monitoring were compiled. Results: 1452 patients underwent cEEG monitoring non-electively from 2007 to 2011. 90 of these patients (6.2%) were found to have PLEDs. Within the population with PLEDs, most cerebral lesions were neoplasms (34.4%), followed by hemorrhage (24.4%) and ischemic stroke (14.4%) (Table 1). 72.2% of patients with PLEDs had seizures detected during monitoring (28.9% purely subclinical; 18.9% purely clinical; 24.4% clinical and subclinical). Overall, 31.1% of patients with PLEDs had independent functionality at discharge; the remainder had poor discharge outcomes (53.3% dependent; 15.6% deceased). Median monitoring duration was 4 days. The majority of PLEDs and seizures were detected on the first day of cEEG monitoring, with greater than 90% of both detected by the second day (Figure 1). In particular, for patients with PLEDs and subclinical seizures, 71.9% of the subclinical seizures were detected on the first day of monitoring, with 91.7% detected by the second day. Conclusions: The frequency of PLEDs was 6.2% in our inpatient series, much higher than reported for routine or mixed inpatient/outpatient EEGs. It appears that an even higher frequency of PLEDs (15.8%) can be inferred from prior data presented by Claassen et al. in a study of critically ill patients undergoing cEEG (Neurology 2004; 62: 1743-1748). Thus, acutely ill patients appear to have much higher rates of PLEDs than commonly recognized based on previous studies involving less acute populations and routine EEGs. Underlying lesions in our PLED patients were primarily neoplastic, likely reflecting institutional trends; nonetheless, this differs from prior literature associating stroke as the most common etiology for PLEDs. More than 90% of all PLEDs, as well as both clinical and subclinical seizures in the patients whom PLEDs were ultimately found, were detected by the second day of cEEG monitoring. These results support the previous work of Claassen et al. by suggesting that patients with PLEDs should undergo cEEG monitoring for at least 2 days to detect subclinical seizures with reasonable sensitivity.