Tracking Multisite Seizure Propagation Using Ictal High-Gamma Activity

Area of Science:

• Neuroscience
• Epileptology
• Computational Neuroscience

Background:

• Epileptic seizure propagation patterns are complex and not fully understood.
• Characterizing seizure spread is crucial for effective epilepsy treatment.

Purpose of the Study:

• To map the spatial evolution of seizure recruitment using high-gamma activity (HGA).
• To identify seizure hubs and understand their role in seizure propagation.

Main Methods:

• Analyzed ictal HGA (80-150 Hz) in 72 seizures from 13 patients using stereotactic depth electrodes.
• Identified spatial clusters of HGA as seizure hubs and analyzed their recruitment patterns.
• Correlated seizure hub activity with seizure termination and compared overlap with interictal ripples.

Main Results:

• Ictal HGA tracked seizure recruitment in 71% of seizures.
• Multiple seizure hubs were found in 54% of cases, including those presumed unifocal.
• Noncontiguous recruitment correlated with asynchronous seizure termination (OR=19.7, p=0.029).

Conclusions:

• Ictal HGA is a biomarker distinguishing contiguous from remote seizure spread.
• Seizure activity clusters in stereotyped hubs, not broadly distributed.
• Multiple hubs are common, even in clinically unifocal epilepsy.