Abstracts

Rationale: Patients often have a routine EEG study prior to admission to the epilepsy monitoring unit (EMU). The diagnostic utility of this has not been recently studied in patients with routine video-EEG recordings. The initial routine EEG may detect interictal epileptiform discharges in 50% of patients, improving to 90% with three EEG recordings¹. Patients with nonepileptic episodic events (NEE) may experience a spell during the routine study obviating the need for long-term EEG recordings. The purpose of this study is to determine the diagnostic yield of spell capture for routine EEG ordered before an EMU admission.

Methods: We queried all EMU admissions for long-term EEG recordings (mean duration 2.5 days) from 5/5/2018-8/1/2020 with routine short-term video-EEG ordered within 30 days of admission at one institution. We reviewed all EMU and routine EEG reports for NEE, generalized or focal seizures, generalized or focal epileptiform discharges, and reviewed routine EEG reports for nonepileptiform abnormalities, e.g., focal slowing. Logistic regression analysis was performed with EMU seizure, NEE, or any event capture as the dependent variable, and age, gender, interictal discharges on routine EEG, and non-epileptiform abnormalities alone on routine EEG as independent variables.

Results: In total, 353 patients met inclusion criteria. Of 38 routine EEGs that recorded any event only 4 (10.5%) did not have a spell/seizure in the EMU; of these 4 events 3 were NEE and 1 was seizure. Seizures were recorded on 9 (2.6%) of routine EEGs and 113 (32%) of subsequent EMU admissions. Epileptiform discharges were identified on 128 (36.3%) of routine EEGs and 189 (53.5%) of subsequent EMU admissions. Routine EEG abnormalities were not associated with the combined spell capture variable after adjustment for age and gender. Epileptiform abnormalities on routine EEG were associated with increased odds of seizure capture in the EMU (OR 5.56, 95% CI 3.17-9.76). Female gender (OR 1.72, 95% CI 1.12-2.65) was associated with increased odds of NEE, while presence of any epileptiform abnormality on routine EEG (OR 0.47, 95% CI 0.28-0.79) was associated with decreased odds of NEE. Only 1 of 29 patients with a routine EEG identified NEE had a recorded seizure in the EMU.

Conclusions: Routine EEG studies may provide important diagnostic and prognostic information that may assist in determining the indication for EMU admission. Patients with routine EEG recorded NEE have a low incidence of seizure in the EMU. The typical nature of the symptoms associated with the NEE did not affect the outcome of the EMU evaluation. The presence of routine EEG recorded epileptiform discharges had a strong prognostic association with seizure capture.

References:
1. Chen, H, Koubeissi, M. Electroencephalography in Epilepsy Evaluation. Continuum (Minneapolis MN), April 2019, Vol.25, No.2
2. Hopp, J. Nonepileptic Episodic Events. Continuum (Minneapolis MN), April 2019, Vol.25, No.2.

Funding: Please list any funding that was received in support of this abstract.: N/A.