Deep Learning Provides Exceptional Accuracy to ECoG-Based Functional Language Mapping for Epilepsy Surgery

Abstract

The success of surgical resection in epilepsy patients depends on preserving functionally critical brain regions, while removing pathological tissues. Being the gold standard, electro-cortical stimulation mapping (ESM) helps surgeons in localizing the function of eloquent cortex through electrical stimulation of electrodes placed directly on the cortical brain surface. Due to the potential hazards of ESM, including increased risk of provoked seizures, electrocorticography based functional mapping (ECoG-FM) was introduced as a safer alternative approach. However, ECoG-FM has a low success rate when compared to the ESM. In this study, we address this critical limitation by developing a new algorithm based on deep learning for ECoG-FM and thereby we achieve an accuracy comparable to ESM in identifying eloquent language cortex. In our experiments, with 11 epilepsy patients who underwent presurgical evaluation (through deep learning-based signal analysis on 637 electrodes), our proposed algorithm obtained an accuracy of 83.05% in identifying language regions, an exceptional 23% improvement with respect to the conventional ECoG-FM analysis (∼60%). Our findings have demonstrated, for the first time, that deep learning powered ECoG-FM can serve as a stand-alone modality and avoid likely hazards of the ESM in epilepsy surgery. Hence, reducing the potential for developing post-surgical morbidity in the language function.

Epileptic Seizures Detection Using Deep Learning Techniques: A Review

“…Ravi Prakash et al [ 135 ] introduced an algorithm based on DL for ECoG-based functional mapping (ECoG-FM) for eloquent language cortex identification. However, the success rate of ECoG-FM is low as compared with electro-cortical stimulation mapping (ESM).…”

Advanced Bioelectrical Signal Processing Methods: Past, Present and Future Approach—Part II: Brain Signals

“…Some clinical sites record from the penetrating micro-electrodes, used in case a tissue with the implanted electrode is damaged, so such penetrating electrode “moves” and in result allows recording from areas with healthy tissue [ 5 ]. The ECoG is performed mainly on patients who will have to have a follow-up resection procedure for sure [ 241 , 242 ]. Figure 9 shows an example of the ECoG signal.…”

“…The ECoG is used mainly to locate the epileptogenic zones during preliminary planning, mapping cortical functions, and prediction of the success of epileptic surgical resection. The ECoG, despite its invasiveness, has several advantages over alternative—non-invasive diagnostic methods [ 242 ]: Flexible placement of recording and stimulation electrodes; It can be performed at any stage before, during and after surgery; It allows direct electrical stimulation of the brain and identification of critical areas of the cortex, which must be avoided during surgery; It provides greater accuracy and sensitivity than the scalp EEG recordings, as the spatial resolution is higher and the signal-to-noise ratio is better due to closer proximity to the neural activity. …”

“…The ECoG is used mainly to locate the epileptogenic zones during preliminary planning, mapping cortical functions, and prediction of the success of epileptic surgical resection. The ECoG, despite its invasiveness, has several advantages over alternative-noninvasive diagnostic methods [242]:…”

Combining Gamma With Alpha and Beta Power Modulation for Enhanced Cortical Mapping in Patients With Focal Epilepsy

“…These studies showed that accepting electrodes with a high response in either the gamma band, the beta band, or in both, as potentially eloquent yielded better results than using either band alone, especially in the language cortex. Likewise, machine- and deep- learning approaches ( Prakash et al, 2017 ; RaviPrakash et al, 2020 ) have shown that using the entire frequency spectrum, rather than only the gamma band, yields better mapping results, although it was not made clear which part of the spectrum offered the most additional information. In addition, while there is considerable heterogeneity in the task employed between studies, few studies have directly compared different tasks in the same group of patients.…”