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Abnormal Synchronization Between Cortical Delta Power and Ripples in Hippocampal Sclerosis
Takamitsu Iwata1, Takufumi Yanagisawa1,2, Ryohei Fukuma1,2
1Department of Neurosurgery, Graduate School of Medicine, Osaka University, Suita, Osaka, Japan.
Annals of Clinical and Translational Neurology
|March 20, 2025
Summary
Distinguishing epileptogenic from physiological hippocampal ripples is challenging. A new method using nocturnal ripple and delta power synchronization (Corr-RD) accurately differentiates these ripples, identifying a key biomarker for hippocampal epileptogenicity.
Area of Science:
- Neuroscience
- Epilepsy Research
- Biomarker Discovery
Background:
- Differentiating epileptogenic (EP) from physiological hippocampal ripples is crucial for identifying EP zones but is challenging based on waveform analysis.
- Hippocampal ripples are key indicators in epilepsy, but their precise classification requires advanced methods.
Purpose of the Study:
- To investigate the hypothesis that nocturnal synchronization of hippocampal ripples and cortical delta power can classify epileptogenic and physiological ripples.
- To establish a novel method for distinguishing between hippocampal ripple types.
Main Methods:
- Intracranial electroencephalography (iEEG) was used in 38 patients (EP group: 11, Nonepileptogenic (NE) group: 5).
- Hippocampal ripples and cortical delta power (0.5-4 Hz) were recorded overnight.
- The Pearson correlation coefficient between ripple rates and delta power (Corr-RD) was calculated.
Main Results:
- Hippocampal ripples showed similar waveforms and frequencies between EP and NE groups.
- The EP group exhibited significantly lower Corr-RD values (0.20 ± 0.049) compared to the NE group (0.67 ± 0.070).
- Classification based on minimum Corr-RD achieved 94.1% accuracy.
Conclusions:
- The nocturnal synchronization of hippocampal ripples and cortical delta power, quantified by Corr-RD, serves as a reliable biomarker for hippocampal epileptogenicity.
- This finding offers a new approach for distinguishing epileptogenic from physiological ripples, aiding in the identification of epilepsy zones.
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