Prevalence of non-convulsive seizure and other electroencephalographic abnormalities in ED patients with altered mental status

Abstract

Four to ten percent of patients evaluated in emergency departments (ED) present with altered mental status (AMS). The prevalence of non-convulsive seizure (NCS) and other electroencephalographic (EEG) abnormalities in this population is unknown.

Objectives: To identify the prevalence of NCS and other EEG abnormalities in ED patients with AMS.

Methods: A prospective observational study at 2 urban ED. Inclusion: patients ≥13 years old with AMS. Exclusion: An easily correctable cause of AMS (e.g. hypoglycemia). A 30-minute standard 21-electrode EEG was performed on each subject upon presentation.

Outcome: prevalence of EEG abnormalities interpreted by a board-certified epileptologist. EEGs were later reviewed by 2 blinded epileptologists. Inter-rater agreement (IRA) of the blinded EEG interpretations is summarized with κ. A multiple logistic regression model was constructed to identify variables that could predict the outcome.

Results: Two hundred fifty-nine patients were enrolled (median age: 60, 54% female). Overall, 202/259 of EEGs were interpreted as abnormal (78%, 95% confidence interval [CI], 73-83%). The most common abnormality was background slowing (58%, 95% CI, 52-68%) indicating underlying encephalopathy. NCS (including non-convulsive status epilepticus [NCSE]) was detected in 5% (95% CI, 3-8%) of patients. The regression analysis predicting EEG abnormality showed a highly significant effect of age (P < .001, adjusted odds ratio 1.66 [95% CI, 1.36-2.02] per 10-year age increment). IRA for EEG interpretations was modest (κ: 0.45, 95% CI, 0.36-0.54).

Conclusions: The prevalence of EEG abnormalities in ED patients with undifferentiated AMS is significant. ED physicians should consider EEG in the evaluation of patients with AMS and a high suspicion of NCS/NCSE.

Trial registration: ClinicalTrials.gov NCT01355211.

Conflict of interest statement

COMPETING INTERESTS

This study was a collaborative effort between investigators from Downstate Medical Center and Bio-Signal Group (BSG) Inc. The study was supported by NIH grant 1RC3NS070658 to Bio-Signal Group Inc. SZ, ACG, RS, GC and JW received salary support through a subcontract to Downstate Medical Center. SGA, SM, AO, are BSG employees. AF is the founder of BSG. ACG serves on the BSG advisory board. All income derived from this position is donated directly from BSG to the Downstate College of Medicine Foundation.

© 2013.

Figures

Figure 1

Schematic for study protocol