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CC BY-NC-ND 4.0 · J Neurol Surg A Cent Eur Neurosurg 2024; 85(03): 294-301
DOI: 10.1055/a-2202-9344
Review Article

Association between Removal of High-Frequency Oscillations and the Effect of Epilepsy Surgery: A Meta-Analysis

Zhichuang Qu‡   *
1   Department of Neurosurgery, Affiliated Hospital of Southwest Medical University, Luzhou, China
2   Department of Neurosurgery, The PLA Western Theater Command General Hospital, Chengdu, China
,
Juan Luo‡   *
1   Department of Neurosurgery, Affiliated Hospital of Southwest Medical University, Luzhou, China
2   Department of Neurosurgery, The PLA Western Theater Command General Hospital, Chengdu, China
,
Xin Chen
2   Department of Neurosurgery, The PLA Western Theater Command General Hospital, Chengdu, China
,
Yuanyuan Zhang
2   Department of Neurosurgery, The PLA Western Theater Command General Hospital, Chengdu, China
3   Southwest Jiaotong University, Chengdu, China
,
Sixun Yu
2   Department of Neurosurgery, The PLA Western Theater Command General Hospital, Chengdu, China
,
Haifeng Shu
1   Department of Neurosurgery, Affiliated Hospital of Southwest Medical University, Luzhou, China
2   Department of Neurosurgery, The PLA Western Theater Command General Hospital, Chengdu, China
3   Southwest Jiaotong University, Chengdu, China
› Author Affiliations
Funding This work was supported by a joint key project (grant number: 2019LH01); Department of Science and Technology of Sichuan Province (grant number: 22CXRC0178); Medical Innovation Project (grant number: 21WQ040); Southwest Jiaotong University Medical and Industrial Combination Training Special Project (grant number: 2682021ZTPY024); Hospital Management Project of Western General Hospital (grant numbers 2021-XZYG-B22); and Hospital Management Project of Western Command General Hospital (grant numbers 2021-XZYG-B21).
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Abstract

Background High-frequency oscillations (HFOs) are spontaneous electroencephalographic (EEG) events that occur within the frequency range of 80 to 500 Hz and consist of at least four distinct oscillations that stand out from the background activity. They can be further classified into “ripples” (80–250 Hz) and “fast ripples” (FR; 250–500 Hz) based on different frequency bands. Studies have indicated that HFOs may serve as important markers for identifying epileptogenic regions and networks in patients with refractory epilepsy. Furthermore, a higher extent of removal of brain regions generating HFOs could potentially lead to improved prognosis. However, the clinical application criteria for HFOs remain controversial, and the results from different research groups exhibit inconsistencies. Given this controversy, the aim of this study was to conduct a meta-analysis to explore the utility of HFOs in predicting postoperative seizure outcomes by examining the prognosis of refractory epilepsy patients with varying ratios of HFO removal.

Methods Prospective and retrospective studies that analyzed HFOs and postoperative seizure outcomes in epilepsy patients who underwent resective surgery were included in the meta-analysis. The patients in these studies were grouped based on the ratio of HFOs removed, resulting in four groups: completely removed FR (C-FR), completely removed ripples (C-Ripples), mostly removed FR (P-FR), and partial ripples removal (P-Ripples). The prognosis of patients within each group was compared to investigate the correlation between the ratio of HFO removal and patient prognosis.

Results A total of nine studies were included in the meta-analysis. The prognosis of patients in the C-FR group was significantly better than that of patients with incomplete FR removal (odds ratio [OR] = 6.62; 95% confidence interval [CI]: 3.10–14.15; p < 0.00001). Similarly, patients in the C-Ripples group had a more favorable prognosis compared with those with incomplete ripples removal (OR = 4.45; 95% CI: 1.33–14.89; p = 0.02). Patients in the P-FR group had better prognosis than those with a majority of FR remaining untouched (OR = 6.23; 95% CI: 2.04–19.06; p = 0.001). In the P-Ripples group, the prognosis of patients with a majority of ripples removed was superior to that of patients with a majority of ripples remaining untouched (OR = 8.14; 95% CI: 2.62–25.33; p = 0.0003).

Conclusions There is a positive correlation between the greater removal of brain regions generating HFOs and more favorable postoperative seizure outcomes. However, further investigations, particularly through clinical trials, are necessary to justify the clinical application of HFOs in guiding epilepsy surgery.

Keywords

high-frequency oscillations - intractable epilepsy - intracranial electrography - epilepsy prognosis - electrocorticogram

* These authors contributed equally to this work and should be regarded as co-first authors.




Publication History

Received: 05 July 2023

Accepted: 11 September 2023

Accepted Manuscript online:
02 November 2023

Article published online:
22 January 2024

© 2024. The Author(s). This is an open access article published by Thieme under the terms of the Creative Commons Attribution-NonDerivative-NonCommercial License, permitting copying and reproduction so long as the original work is given appropriate credit. Contents may not be used for commercial purposes, or adapted, remixed, transformed or built upon. (https://creativecommons.org/licenses/by-nc-nd/4.0/)

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