Detection of epileptic activity in fMRI without recording the EEG

R. Lopes*, J. M. Lina, F. Fahoum, J. Gotman

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

EEG-fMRI localizes epileptic foci by detecting cerebral hemodynamic changes that are correlated to epileptic events visible in EEG. However, scalp EEG is insensitive to activity restricted to deep structures and recording the EEG in the scanner is complex and results in major artifacts that are difficult to remove.This study presents a new framework for identifying the BOLD manifestations of epileptic discharges without having to record the EEG. The first stage is based on the detection of epileptic events for each voxel by sparse representation in the wavelet domain. The second stage is to gather voxels according to proximity in time and space of detected activities.This technique was evaluated on data generated by superposing artificial responses at different locations and responses amplitude in the brain for 6 control subject runs. The method was able to detect effectively and consistently for responses amplitude of at least 1% above baseline. 46 runs from 15 patients with focal epilepsy were investigated. The results demonstrate that the method detected at least one concordant event in 37/41 runs. The maps of activation obtained from our method were more similar to those obtained by EEG-fMRI than to those obtained by the other method used in this context, 2D-Temporal Cluster Analysis. For 5 runs without event read on scalp EEG, 3 runs showed an activation concordant with the patient's diagnostic.It may therefore be possible, at least when spikes are infrequent, to detect their BOLD manifestations without having to record the EEG.

Original languageEnglish
Pages (from-to)1867-1879
Number of pages13
JournalNeuroImage
Volume60
Issue number3
DOIs
StatePublished - 15 Apr 2012
Externally publishedYes

Funding

FundersFunder number
Canadian Institutes of Health Research

    Keywords

    • Activelets
    • Clustering
    • Epilepsy
    • FMRI
    • Hemodynamic response function
    • Sparse representation

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