Tracking cognitive changes in new-onset epilepsy: Functional imaging challenges

Spatial MEG laterality maps for language: clinical applications in epilepsy

Functional imaging is increasingly being used to provide a noninvasive alternative to intracarotid sodium amobarbitol testing (i.e., the Wada test). Although magnetoencephalography (MEG) has shown significant potential in this regard, the resultant output is often reduced to a simplified estimate of laterality. Such estimates belie the richness of functional imaging data and consequently limit the potential value. We present a novel approach that utilizes MEG data to compute "complex laterality vectors" and consequently "laterality maps" for a given function. Language function was examined in healthy controls and in people with epilepsy. When compared with traditional laterality index (LI) approaches, the resultant maps provided critical information about the magnitude and spatial characteristics of lateralized function. Specifically, it was possible to more clearly define low LI scores resulting from strong bilateral activation, high LI scores resulting from weak unilateral activation, and most importantly, the spatial distribution of lateralized activation. We argue that the laterality concept is better presented with the inherent spatial sensitivity of activation maps, rather than being collapsed into a one-dimensional index.

Neuroimaging in epilepsy: the state of the art

Our understanding of epileptogenesis is still limited. Knowledge is increasing with regard to structural and functional changes in chronic stages of epilepsy. At the same time, we have to appreciate that there is a significant lack of such information in new-onset epilepsy. The First Halifax International Epilepsy Conference tried to fill this gap, focusing on the contribution of advanced neuroimaging in early stages of epilepsy. The following article aims to synthesize the themes that emerged from this meeting. Participants agreed that (1) there is a need for a unified theory of epileptogenesis, addressing the interplay of functional and structural brain changes; (2) neuroimaging reveals widespread brain alterations in epilepsy; (3) advances in neuroimaging challenge the concept of "MRI-negative" (magnetic resonance imaging negative) focal epilepsy; (4) methodologic limitations and potential confounders must be considered in the translation of innovative imaging approaches to clinical practice; and (5) there is an urgent need for longitudinal studies that begin early in the disease process.