Source reconstruction of mesial-temporal epileptiform activity: Comparisonof inverse techniques

Purpose: To evaluate whether advanced source reconstruction such as current density reconstruction (CDR) provides additional hints for clinical presur gical evaluation, different source reconstruction techniques with idealized spherical as well as realistically shaped head models (boundary element me thod, BEM) were applied on interictal and ictal epileptiform activity in pr esurgical evaluated patients with temporal lobe epilepsy. It is discussed w hether CDR and BEM give additional information for presurgical evaluation c ompared to "conventional" strategies, such as single moving, and spatio-tem poral dipole modeling with spherical head models. Methods: A variety of source reconstruction procedures were applied to the data of five patients with pharmacoresistent temporal lobe epilepsy with pr obable mesial origin: (1) single-moving dipole in a spherical head model an d (2) in BEM, (3) spatio-temporal dipole modeling in a spherical head model and (4) in BEM; and (5) deconvolution with fixed locations and orientation s and (6) with cortically constrained L1-norm CDR in BEM. In addition, simu lated sources of temporal lobe origin were calculated in each subject with CDR to prove the basic feasibility of this technique in the particular appl ication. Results: Source activity was correctly localized within the affected tempor al lobe by all source reconstruction techniques used. Neither single moving dipole, spatio-temporal modeling, nor CDR was able to localize sources at a sublobar level. In the case of two sources, single moving dipole solution s showed changes in dipole orientation in time and spatio-temporal modeling separated two sources, whereas CDR at the peak latency failed to distingui sh among different origins. BEM enhanced localization accuracy. Conclusion: There was no advantage of using CDR. Single moving dipole as we ll as spatio-temporal dipole modeling in BEM leads to more precise localiza tion within the individual anatomy and provides a simple algorithm, which i s capable of indicating bath the time course and the number of sources.