Spike-fast activity interplay: A gateway to seizure
Thandar Aung1, Aude Jegou1, Patrick Chauvel2
1Epilepsy Center, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania, USA.
Epilepsia
|October 31, 2025
Summary
Seizure onset involves a gradual transition from interictal spike-associated high-frequency oscillations (Sp-HFOs) to ictal high-frequency activity (HFA). This preparatory phase, characterized by increasing frequency similarity, may offer biomarkers for seizure prediction.
Area of Science:
- Neuroscience
- Epilepsy Research
- Signal Processing
Background:
- The transition from interictal to ictal activity in focal epilepsy is not fully understood.
- Investigating the role of spike-associated high-frequency oscillations (Sp-HFOs) in this transition is crucial.
Purpose of the Study:
- To determine if Sp-HFOs during interictal and preictal periods contribute to the emergence of ictal high-frequency activity (HFA).
- To analyze the frequency dynamics of the interictal-ictal transition in drug-resistant focal epilepsy.
Main Methods:
- Retrospective analysis of stereo-EEG data from six epilepsy patients.
- Time-frequency analysis (TFA) to characterize Sp-HFOs and ictal HFA.
- Utilized the novel Ideal Fusion (I-Fusion) metric to quantify frequency overlap and band matching.
Main Results:
- A preictal phase was identified where brief HFA within Sp-HFOs evolved into sustained ictal HFA.
- Increasing frequency similarity over time was observed between Sp-HFOs and ictal HFA.
- Sp-HFOs and ictal HFA exhibited shared narrow-band frequency features, particularly in the epileptogenic zone (EZ).
Conclusions:
- Seizure onset is preceded by a gradual, frequency-specific preparatory phase, not an abrupt transformation.
- The progressive nature of Sp-HFOs suggests increasing neuronal synchrony.
- Sp-HFOs may serve as early biomarkers for seizure prediction and EZ localization.
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