Toxic metabolic encephalopathy (TME) is a common indication for continuous EEG (cEEG) monitoring. The prevalence of ictal-interictal continuum (IIC) patterns in pure TME, their relation to outcome and treatment implications remain unclear. Here we evaluate the frequency, clinical predictors, and prognostic value of IIC patterns in TME. 

 We included patients with TME undergoing cEEG for > 18 hours. Patients with acute structural brain injury or cardiac arrest were excluded. Age, gender, APACHE II score, underlying etiology, and 3 month MRS were ascertained by chart review. IIC patterns (seizures, lateralized and generalized periodic discharges, lateralized rhythmic delta activity, sporadic discharges) were defined using the American Clinical Neurophysiology nomenclature. 

121 patients met study criteria (mean age 64 years; 54.6 % female; mean APACHE II score 20). The most common etiologies for TME were renal (48%), hepatic (36%) and pulmonary (31%). 100 (82.6%) of patients had IIC patterns. Patients with IIC had higher APACHE II score ( median 21 vs 16, p = 0.04) and were more likely to have hepatic failure (OR 1.17, p = 0.03). Hepatic disease (OR 4.14, p = 0.04) was independently associated with presence of IIC patterns on multivariate analysis. 84.5% of patients had poor 3-month outcome (MRS 4-6). Although there was a trend towards worse outcomes in patients with IIC, this was not statistically significant (OR 1.16, p = 0.07) 

Patients with TME have a high prevalence of IIC patterns. Patients with underlying hepatic disease are at highest risk. Although there was no significant association of IIC with outcomes, given the high proportion of poor outcomes, our study may be under-powered. Future prospective studies are needed to delineate the long-term impact of IIC in patients with TME to identify candidates for treatment.