Bispectral Electroencephalography for Detection and Monitoring of ICANS After CAR T-Cell Therapy

Immune effector cell-associated neurotoxicity syndrome (ICANS) is a common and potentially severe complication of chimeric antigen receptor (CAR) T-cell therapy. Current diagnosis and monitoring rely primarily on bedside neurological assessments, whereas conventional electroencephalography (EEG) is resource intensive and impractical for routine screening. We evaluated whether portable bispectral EEG (BSEEG), a quantitative EEG-based measure, could provide an objective approach for detecting and monitoring ICANS. In this prospective observational study, 85 adult patients receiving CAR T-cell therapy at Stanford Health Care between August 2023 and April 2025 underwent daily single-channel EEG recordings from pre-infusion until hospital discharge. ICANS was graded according to American Society for Transplantation and Cellular Therapy criteria, and grade ≥ 3 was defined as severe ICANS. Temporal BSEEG trajectories and discriminatory performance were evaluated. Seventeen patients (20%) developed severe ICANS. Patients with severe ICANS demonstrated persistently elevated BSEEG values beginning approximately 3 days after infusion, whereas patients without severe ICANS showed transient early increases followed by stabilization. Maximum BSEEG values were higher in severe ICANS than in non-severe ICANS (2.00 vs. 1.71; p < 0.001) and yielded an area under the curve (AUC) of 0.76, with an optimal cutoff of 1.98 (sensitivity 64.7%, specificity 95.6%). The change from baseline to peak BSEEG values improved discrimination (AUC of 0.82; optimal cutoff 0.41; sensitivity 75.0%, specificity 85.3%). Portable single-channel BSEEG may offer a feasible, noninvasive, and objective approach for identifying and longitudinally monitoring severe ICANS and may complement bedside clinical assessments after CAR T-cell therapy.