Intrahippocampal ripple propagation (RonO) is proportionally greater in less-irritative non-seizure onset zone hippocampus than in epileptogenic hippocampus.
In a study of 49 patients with hippocampal contacts, intrahippocampal propagation of ripples on oscillations (RonO, 80-250 Hz) was highest in less-irritative non-SOZ tissue (with <6 IED/min) compared to more-irritative non-SOZ (>6 IED/min) and SOZ tissue (p<0.05 and p<0.001, respectively). This suggests that RonO propagation may serve as a metric to quantify hippocampal epileptogenicity along a continuous spectrum.
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Intrahippocampal ripple propagation (RonO) is proportionally greater in less-irritative non-seizure onset zone hippocampus than in epileptogenic hippocampus. The current body of evidence comprises 1 study. EvidenceHub rates the overall confidence at 34/100 (low).
The Claim
Intrahippocampal ripple propagation (RonO) is proportionally greater in less-irritative non-seizure onset zone hippocampus than in epileptogenic hippocampus.
This conclusion is most relevant to: 49 patients (68 hemispheres) with verified hippocampal contacts undergoing stereo-EEG during non-REM sleep..
What the Research Shows
The conclusion draws on 1 linked study. Highlights from the cited literature:
- ▸Epileptogenicity alters intrahippocampal ripple propagation. (medRxiv : the preprint server for health sciences, 2026) —
How It Works
The proposed biological pathway:
- ▸Hippocampal tissue is stratified by epileptogenicity based on IED rate and seizure onset.
- ▸Empirical temporal networks of HFO propagation are constructed from stereo-EEG data.
- ▸Proportion of significant propagating RonO is compared across groups.
- ▸Less-irritative non-SOZ hippocampus shows higher intrahippocampal RonO propagation than more epileptogenic tissue.
Who Might Benefit
Evidence fit by population:
- ▸49 patients (68 hemispheres) with verified hippocampal contacts undergoing stereo-EEG during non-REM sleep.
Recommended Dose
N/A
Limitations & Caveats
Important context when interpreting this evidence:
- ▸The study is observational and based on a specific patient population with drug-resistant epilepsy, limiting generalizability.
- ▸Distinguishing physiological from pathological RonO using signal features alone remains challenging, and the classification of epileptogenicity may not capture all nuances.
Frequently Asked Questions
What are ripples on oscillations (RonO)?▼
RonO are high-frequency oscillations in the 80-250 Hz range that occur on top of slower oscillations, often studied in the context of epilepsy and memory.
How was hippocampal epileptogenicity measured in this study?▼
Hippocampi were stratified into three groups: seizure onset zone (SOZ), more-irritative non-SOZ (>6 interictal epileptiform discharges per minute), and less-irritative non-SOZ (<6 IED/min).
Does this study suggest that RonO propagation can help identify epileptogenic tissue?▼
Yes, the authors propose that intrahippocampal RonO propagation may serve as a novel metric to quantify hippocampal epileptogenicity, with lower propagation indicating more pathological tissue.
Were there any differences in fast ripple propagation (FRonO) across groups?▼
No, the study found no significant differences in FRonO (250-600 Hz) propagation proportions across the hippocampal epileptogenicity spectrum, despite their rates being elevated in SOZ.
References
- 1.Chen Y, Ye H, Ye L, Hu L, Chen C, Staba R, Wang S, Weiss SA. “Epileptogenicity alters intrahippocampal ripple propagation..” medRxiv : the preprint server for health sciences, 2026. PMID: 42369499 DOI: 10.64898/2026.06.13.26355594