Spikes with and without concurrent high-frequency oscillations: Topographic relationship and neural correlates using
Javier Urriola1, Steffen Bollmann2, Fred Tremayne3
1Centre for Advanced Imaging, The University of Queensland, Brisbane, Australia.
Epilepsy Research
|November 4, 2022
Summary
Interictal spikes with and without high-frequency oscillations (HFOs) in epilepsy patients show different scalp voltage patterns but similar brain activity. This suggests that both spike types originate from the same underlying epileptic neural networks, aiding surgical target identification.
Area of Science:
- Neuroscience
- Clinical Neurology
- Medical Imaging
Background:
- Epilepsy surgery is a key treatment for drug-resistant focal epilepsy.
- Interictal spikes are crucial for presurgical evaluation, aiding in localizing the seizure origin.
- High-frequency oscillations (HFOs) concurrent with spikes may offer more reliable indicators of epileptogenic tissue.
Purpose of the Study:
- To investigate the voltage distribution of scalp-recorded interictal spikes with and without concurrent HFOs.
- To identify the hemodynamic correlates of these different spike populations using simultaneous EEG-fMRI.
- To compare the spatial and strength characteristics of the hemodynamic responses elicited by spikes with and without HFOs.
Main Methods:
- Assessed scalp topography of spikes with and without HFOs in 31 drug-resistant focal epilepsy patients.
- Utilized simultaneous electroencephalography and functional magnetic resonance imaging (EEG-fMRI) in 17 patients.
- Correlated EEG voltage maps with fMRI BOLD signals to determine hemodynamic responses and compared their spatial similarity, strength, and peak distances.
Main Results:
- Most spikes (25/31 patients) were not associated with HFOs.
- Significant scalp voltage differences were observed in 20/25 patients.
- No significant differences were found in the hemodynamic response's peak strength, spatial distribution, or activation peak distance between spikes with and without HFOs.
Conclusions:
- Spikes with and without HFOs exhibit distinct scalp voltage distributions.
- Despite differing scalp patterns, both spike types induce similar hemodynamic changes and share high spatial similarity.
- These findings suggest that spikes with and without HFOs arise from the same underlying epileptic neural networks, providing a unified target for epilepsy surgery.
