Combined EEG-fMRI and ESI improves localisation of paediatric focal epilepsy

ABSTRACT

Objective

Surgical treatment in epilepsy is effective if the epileptogenic zone (EZ) can be correctly localized and characterized. Here we use simultaneous Electroencephalography-functional MRI (EEG-fMRI) data to derive EEG-fMRI and Electrical Source Imaging (ESI) maps. Their yield and their individual and combined ability to 1) localize the epileptogenic zone and 2) predict seizure outcome was then evaluated.

Methods

Fifty-three children with drug-resistant epilepsy underwent EEG-fMRI. Interictal discharges were mapped using both EEG-fMRI haemodynamic responses and Electrical Source Imaging (ESI). A single localization was derived from each individual test (EEG-fMRI global maxima (GM)/ESI maxima) and from the combination of both maps (EEG-fMRI/ESI spatial intersection). To determine the localisation accuracy and its predictive performance the individual and combined test localisations were compared to the presumed EZ and to the postsurgical outcome.

Results

Fifty-two/53 patients had significant maps; 47/53 for EEG-fMRI; 44/53 for ESI; 34/53 had both. The epileptogenic zone was well characterised in 29 patients; 26 had an EEG-fMRI GM localisation which was correct in 11; 22 patients had ESI localisation which was correct in 17; 12 patients had combined EEG-fMRI and ESI which was correct in 11.

Seizure outcome following resection was correctly predicted by EEG-fMRI GM in 8/20 patients, by the ESI maxima in 13/16. The combined EEG-fMRI/ESI region entirely predicted outcome in 9/9 patients including 3 with no lesion visible on MRI.

Interpretation

EEG-fMRI combined with ESI provides a simple unbiased localisation that may predict surgery better than each individual test including in MRI-negative patients. This article is protected by copyright. All rights reserved.

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