Abstracts

Rationale: Precise identification of epileptic spikes in interictal EEG is an important step in simultaneous EEG-functional MRI (EEG-fMRI) analysis of epilepsy. But, it is a tedious and subjective task for human experts. Our aim is to facilitate EEG mark-up for epileptologists through a software package of automatic spike detection and EEG-fMRI analysis. Methods: We implemented a set of mathematical algorithms for automatic detection and clustering (i.e., grouping together different types) of interictal epileptiform discharges in MATLAB. We tested the applicability of these algorithms using scalp EEG recordings in 16 patients with refractory focal epilepsy who underwent a one-hour EEG-fMRI scan. Results: Automatic interictal epileptiform discharges detectionhas short processing time (<1 min) and provides greater statistical power in EEG-fMRI compared to human markup only. In six cases, we identified additional activated brain regions not seen in standard analysis based solely on human EEG markup. Figure 1 shows an example where automatic spike detection has revealed new brain activations which have been in line with other clinical information. Figure 2 illustrates the results of 13 datasets using spike detection and human markup. The activation maps associated with newly detected spikes (those which haven't been marked by the expert) have also been presented in the very right column. Conclusions: The software package reproduces comparable and, in some cases, even superior results in EEG-fMRI analysis of epilepsy, as compared to the current standard approach. Our results suggest that EEG event detection algorithms can be integrated into clinical settings. We are releasing our algorithms freely available as an easy-to-use MATLAB toolbox.  Funding: This study was supported by the National Health and Medical Research Council (NHMRC) of Australia (#628952). The Florey Institute of Neuroscience and Mental Health acknowledges the strong support from the Victorian Government and in particular the funding from the Operational Infrastructure Support Grant. We also acknowledge the facilities, and the scientific and technical assistance of the National Imaging Facility (NIF) at the Florey node and The Victorian Biomedical Imaging Capability (VBIC).