Presurgical electromagnetic functional brain mapping in refractory focal epilepsy

Abstract

Background: Electroencephalography (EEG) and magnetoencephalography (MEG) are neurophysiological methods used to investigate non-invasively the spatial, temporal and spectral dynamics of human brain functions. Objectives: This paper reviews data about the use of EEG and MEG for presurgical functional brain mapping in patients with refractory focal epilepsy. Focus is on the localization of the primary sensorimotor (SM1) cortex as well as the verbal language and episodic memory functions. Material and Methods: The English literature was reviewed based on PubMed search. Relevant references within the selected papers were also included. Results: Presurgical MEG functional localization of SM1 cortex generally overlaps with intracranial mapping. MEG allows for determination of hemispheric verbal (receptive and expressive) language dominance in neurosurgical patients with a high degree of concordance with the intracarotid amobarbital test. MEG represents an interesting technique to assess postoperative memory outcome in patients with mesial temporal lobe epilepsy. Very few studies have evaluated the yield of EEG in these three clinical indications. High-density EEG might be a promising technique that needs further validation. Conclusions: MEG is a validated and robust technique for non-invasive functional mapping of SM1 cortex and verbal language hemispheric dominance in patients with refractory focal epilepsy. Data also suggest that MEG is a promising technique to assess the hemispheric dominance of memory function. Further studies are needed to assess the clinical added value of high-density EEG in these clinical indications.

Presurgical Functional Cortical Mapping Using Electromagnetic Source Imaging

“…fMRI possibly provides better prediction of postoperative verbal language and memory deficits compared to IAT (50, 51), and shows concordance with IAT results in about 80–90% of cases (8). fMRI holds the potential to replace IAT for determination of hemispheric language dominance in many cases (5, 52). However, sites of fMRI activation do not necessarily reflect cortex essential for verbal language function and conversely, areas not activated by the fMRI paradigm under use may prove to be relevant (5).…”

Exploring Kainic Acid-Induced Alterations in Circular Tripartite Networks with Advanced Analysis Tools

“…The complexity of the human brain hinders the development of novel treatments. Conventional neuroimaging tools such as EEG, MEG ( Coolen et al, 2018 ), and fMRI ( Centeno and Carmichael, 2014 ; Lewis et al, 2016 ) provide researchers with macrolevel brain functional data but have limited spatial and temporal resolution ( Depannemaecker et al, 2022 ; Ihle et al, 2022 ). On the other hand, microelectrode array (MEA) recordings enable the collection of information from hundreds of neurons, e.g., in epileptic patients ( Peyrache et al, 2012 ; Dehghani et al, 2016 ; Paulk et al, 2022 ).…”