Feasibility of EEG Phase‐Amplitude Coupling to Stratify Encephalopathy Severity in Neonatal HIE Using Short Time Window

Goal: It is challenging to clinically discern the severity of neonatal hypoxic ischemic encephalopathy (HIE) within hours after birth in time for therapeutic decision‐making for hypothermia. The goal of this study was to determine the shortest duration of the EEG based PAC index to provide real‐time guidance for clinical decision‐making for neonates with HIE. Methods: Neonates were recruited from a single‐center Level III NICU between 2017 and 2019. A time‐dependent, PAC-frequency‐averaged index, tPACm, was calculated to characterize intrinsic coupling between the amplitudes of 12–30 Hz and the phases of 1–2 Hz oscillation from 6‐h EEG data at electrode P3 during the first day of life, using different sizes of moving windows including 10 s, 20 s, 1 min, 2 min, 5 min, 10 min, 20 min, 30 min, 60 min, and 120 min. Time‐dependent receiver operating characteristic (ROC) curves were generated to examine the performance of the accurate window tPACm as a neurophysiologic biomarker. Results: A total of 33 neonates (mild‐HIE, n = 15 and moderate/severe HIE, n = 18) were enrolled. Mixed effects models demonstrated that tPACm between the two groups was significantly different with window time segments of 3–120 min. By observing the estimates of group differences in tPACm across different window sizes, we found 20 min was the shortest window size to optimally distinguish the two groups (p < 0.001). Time‐varying ROC showed significant average area‐under‐the‐curve of 0.82. Conclusion: We demonstrated the feasibility of using tPACm with a 20min EEG time window to differentiate the severity of HIE and facilitate earlier diagnosis and treatment initiation.