Othr-11. Title: Electrographic Seizures and Eeg Background Features in Pediatric Neuro-Oncology Patients Admitted to the Pediatric Intensive Care Unit

BACKGROUND Electrographic seizures (ES) are common in critically ill children with the incidence of ES ranging from 10-50%. Continuous EEG (cEEG) is frequently obtained in children with brain tumors due to encephalopathy or concern for seizures. Despite this, little is known about the incidence of ES, EEG background features, or the impact of EEG on clinical management in this population. METHODS This is a prospective single center study of critically ill children with brain tumors admitted to the pediatric intensive care unit (PICU) from July 2021 to July 2023. Patients with new or known primary brain tumors and cEEG completed during their admission were included. We excluded patients with planned admissions for EEG. Clinical variables included age, sex, oncologic diagnosis, tumor grade and location, indication for EEG, EEG features, and changes in management. RESULTS Thirty-six patients were identified who met the inclusion criteria. 21 patients were female. The median age was 11.0 years (IQR 6.6– 15.4 years). The most common indication for EEG was encephalopathy in 42% followed by clinical seizure in 31%. ES were captured in 19% (7/36) with the majority being subclinical; in patients with acute encephalopathy, ES were captured in 20% (3/15). The EEG background was abnormal in 97% of cases. The most common EEG background was slow disorganized with background asymmetry seen in in 74%. EEG background features met criteria for the ictal-interictal continuum in 14%. A higher rate of ES was seen in patients with disseminated tumors (p=0.03) and severe encephalopathy on EEG (p=0.006). EEG led to a change in management in 31% of patients. CONCLUSIONS ES are common in critically ill children with brain tumors and would go undetected without cEEG. EEG findings often led to a change in clinical management and is a vital tool for the evaluation of this population.