A robust implementation of a kurtosis beamformer for the accurate identification of epileptogenic foci

Objective: To improve the accuracy and reliability of the localisation of epileptogenic activity using spatially filtered MEG data. Methods: A synthetic epileptic source was embedded in healthy brain activity in different orientations in order to estimate how reliably this signal containing high levels of kurtosis can be localised. An existing approach (SAM(g2)) was compared to a new implementation of the methodology. Results: The results confirm that a kurtosis beamformer is an effective tool with which to localise spontaneous epileptiform activity. However, it is crucial that the orientation of source reconstruction matches that of the true source otherwise the epileptic activity is either mis-localised or completely missed. Therefore as the original SAM(g2) implementation is restricted to the tangential plane, in certain circumstances it will perform poorly compared to the approach described here. Conclusions: A kurtosis beamformer is made more accurate and more robust if the analysis is not restricted to the tangential plane and if the optimisation routine for selecting the source orientation is performed using kurtosis rather than power. Significance: MEG is increasingly being used for the non-invasive localisation of epileptic biomagnetic signals and the implementation described in this paper increases the clinical utility of the technique. © 2012 International Federation of Clinical Neurophysiology.