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Intrahippocampal ripple propagation proportion is highest in less-irritative non-seizure onset zone hippocampus compared to epileptogenic hippocampus

In a study of 49 patients (68 hemispheres) with hippocampal contacts, intrahippocampal propagation of ripples on oscillations (RonO, 80-250 Hz) was proportionally greater in less-irritative non-SOZ tissue (<6 IED/min) than in more-irritative non-SOZ (>6 IED/min) and seizure onset zone (SOZ) tissue. This suggests RonO propagation may serve as a metric to quantify hippocampal epileptogenicity along a continuous spectrum.

Last updated: Jul 7, 2026•0 RCTs•📖 Read as article →

Evidence Score

Evidence Score34/100
Human RCT☆☆☆☆☆
Meta-analysis☆☆☆☆☆
Mechanism★★★★★
Safety★★★★☆
Confidencelow

Study Evidence

Study 1. Epileptogenicity alters intrahippocampal ripple propagation.

observational

Chen Y, Ye H, Ye L, Hu L, Chen C, Staba R, Wang S, Weiss SA · medRxiv : the preprint server for health sciences (2026)

Participants: N/A
Duration: N/A
Intervention: Comparison of hippocampal groups stratified by epileptogenicity: seizure onset zone (SOZ), more-irritative non-SOZ (>6 IED/min), and less-irritative non-SOZ (<6 IED/min).
Outcome: Proportion of statistically significant propagating RonO (80-250 Hz) and FRonO (250-600 Hz) originating from hippocampal contacts.
Effect Size: N/A (p-values reported: p<0.05 and p<0.001 for group comparisons)
Population: 49 patients (68 hemispheres) with verified hippocampal contacts undergoing non-REM sleep stereo-EEG.

Result:

PubMed: 42369499DOI: 10.64898/2026.06.13.26355594

Mechanism Graph

Hippocampal tissue is stratified by excitability based on IED rate and seizure onset
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Empirical temporal networks of HFO propagation are constructed with 150 ms maximum latency
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Significant propagation pathways are validated against 1000 permutation-generated surrogates
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Intrahippocampal RonO propagation proportion is highest in less-irritative non-SOZ tissue

Limitations

  • ⚠Study uses a preprint (medRxiv) and has not undergone peer review
  • ⚠Distinguishing physiological from pathological RonO using signal features alone remains challenging
  • ⚠Sample size is moderate (49 patients) and may limit generalizability

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 ongoing brain oscillations, measured during non-REM sleep in this study.

How was hippocampal epileptogenicity measured?▼

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).

Did the study find differences in fast ripple propagation?▼

No, propagation proportions for fast ripples (250-600 Hz) did not differ significantly across the hippocampal epileptogenicity spectrum, even though their rates were elevated in SOZ.

What is the clinical implication of this finding?▼

The authors suggest that intrahippocampal RonO propagation may serve as a novel metric to quantify hippocampal epileptogenicity, potentially aiding in surgical planning for epilepsy.

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References

  1. 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
Disclaimer: This content is for educational purposes only and is not medical advice. Evidence scores reflect the quality and quantity of available research, not clinical recommendations. Always consult a healthcare professional before starting any supplement or intervention.