Authors :
Presenting Author: Ayushe Sharma, PhD – Yale University School of Medicine
Aya Khalaf, PhD – Yale
Stefan Sumsky, PhD – Yale University School of Medicine
Sandor Beniczky, PhD – Danish Epilepsy Center
Hal Blumenfeld, MD, PhD – Yale University
Rationale:
Childhood absence epilepsy (CAE) spike-and-wave discharges may present with or without consciousness impairment, yet the neural mechanisms underlying this variability remain poorly understood. Understanding how pre-ictal brain state changes prepare for different seizure outcomes may provide insights into consciousness mechanisms. The pre-ictal arousal state influences absence seizure likelihood, and recent animal model studies indicate that pre-ictal low-frequency cortical activity gradually rises for tens of seconds before seizure onset, while high-frequency activity also increases during this period.Methods:
We collected electroencephalogram (EEG) data from 33 CAE patients (167 seizures, ~50% consciousness-spared) via two Yale CAE studies and the Danish Epilepsy Center. Behavioral assessments during EEG monitoring determined consciousness status. Preprocessing of EEG data included resampling (500 Hz), signal filtering (1 Hz high-pass, 60 Hz notch), re-referencing, and artifact removal. We analyzed pre-ictal spectral power in the 30 s before seizure onset across five frequency bands: delta (1-4 Hz), theta (4-8 Hz), alpha (8-13 Hz), beta (13-30 Hz), and gamma (30-60 Hz). Log-transformation and baseline-correction of power used a 2-second reference period immediately preceding seizures.
Results:
A spectral crossover pattern emerged where consciousness-impaired seizures exhibited higher delta but lower high-frequency power than consciousness-spared seizures during the 30 s before seizure onset. Delta and theta frequency power were specifically greater for impaired seizures, while beta and gamma frequency power were greater for spared seizures. No significant differences in alpha frequency power occurred during the 30 s preceding seizure onset. Conclusions:
These results indicate that pre-ictal spectral patterns exhibit frequency-dependent differences distinguishing consciousness outcomes in absence seizures. Different neural mechanisms preparing the brain for consciousness-sparing versus consciousness-impairing seizures are suggested by the spectral crossover from delta to gamma bands. Differences in arousal state, seizure initiation mechanisms, or both may be reflected by these pre-ictal spectral differences, influencing subsequent electrophysiological and behavioral seizure severity. Further investigation of these mechanisms could enable improved treatments for predicting and preventing consciousness-impairing seizures, enhancing quality of life.
Funding:
This work was supported by the NIH R37NS100901, R01 NS055829 (to HB), the Mark Loughridge and Michele Williams Foundation, and the Betsy and Jonathan Blattmachr family.