Localization of the Epileptogenic Zone by Multimodal Neuroimaging and High-Frequency Oscillation

Abstract

Accurate localization of the epileptogenic zone (EZ) is a key factor to obtain good surgical outcome for refractory epilepsy patients. However, no technique, so far, can precisely locate the EZ, and there are barely any reports on the combined application of multiple technologies to improve the localization accuracy of the EZ. In this study, we aimed to explore the use of a multimodal method combining PET-MRI, fluid and white matter suppression (FLAWS)—a novel MRI sequence, and high-frequency oscillation (HFO) automated analysis to delineate EZ. We retrospectively collected 15 patients with refractory epilepsy who underwent surgery and used the above three methods to detect abnormal brain areas of all patients. We compared the PET-MRI, FLAWS, and HFO results with traditional methods to evaluate their diagnostic value. The sensitivities, specificities of locating the EZ, and marking extent removed versus not removed [RatioChann(ev)] of each method were compared with surgical outcome. We also tested the possibility of using different combinations to locate the EZ. The marked areas in every patient established using each method were also compared to determine the correlations among the three methods. The results showed that PET-MRI, FLAWS, and HFOs can provide more information about potential epileptic areas than traditional methods. When detecting the EZs, the sensitivities of PET-MRI, FLAWS, and HFOs were 68.75, 53.85, and 87.50%, and the specificities were 80.00, 33.33, and 100.00%. The RatioChann(ev) of HFO-marked contacts was significantly higher in patients with good outcome than those with poor outcome (p< 0.05). When intracranial electrodes covered all the abnormal areas indicated by neuroimaging with the overlapping EZs being completely removed referred to HFO analysis, patients could reach seizure-free (p < 0.01). The periphery of the lesion marked by neuroimaging may be epileptic, but not every lesion contributes to seizures. Therefore, approaches in multimodality can detect EZ more accurately, and HFO analysis may help in defining real epileptic areas that may be missed in the neuroimaging results. The implantation of intracranial electrodes guided by non-invasive PET-MRI and FLAWS findings as well as HFO analysis would be an optimized multimodal approach for locating EZ.

Prognostic Value of Complete Resection of the High-Frequency Oscillation Area in Intracranial EEG

“…Our subanalyses identified a high combined prognostic value of complete resection of FR and ripple areas in HFO rate threshold subgroup, only if an HFO rate threshold was applied. Jiang et al 43 and Li et al 44 set up a quantitative threshold (HFO rate >1 event per minute). Thresholding can also be established using statistical guideline, including 95% HFO rate distributions, 19 , 37 statistical dispersion (e.g., Tukey Fence), 10 , 15 and standard deviation (e.g., Kittler method).…”

Computerized application for epilepsy in China: Does the era of artificial intelligence comes?

“…In 2020, Zhou et al 87 trained an SVM model to distinguish enrolled mesial temporal lobe epilepsy patients with the highest accuracy of 84% based on functional and structural neuroimaging information. Subsequently, Li et al 88 accurately localized EZ by combining automated analysis on multimodal neuroimaging and HFOs with the assistance of computers. Meanwhile, Wu et al 89 explored the whole‐brain hyper‐ and hypometabolism based on a multivariate machine learning approach, and this study not only reached a superior discrimination accuracy (>95%) but also identified the most important regional predictors.…”

High-Frequency Oscillations and Epileptogenic Network

“…They are believed to participate in the overall epilepsy pathological process, including both seizure generation and propagation. High-rate HFOs are often found in the seizure onset zone (SOZ) and EZ, and removal of areas generating high-rate HFOs tends to yield better outcomes [ 26 - 28 ]. Due to the limited generating volume of HFOs, it was previously believed that HFOs could not propagate, limiting the discussion of the relationships between HFOs and the epileptogenic network [ 29 ].…”