Effects of Repetitive Transcranial Magnetic Stimulation on Spike Pattern and Topography in Patients with Focal Epilepsy

Repetitive Transcranial Magnetic Stimulation (rTMS) is a non-invasive method for brain stimulation. Group-studies applying rTMS in epilepsy patients aiming to decrease epileptic spike- or seizure-frequency have led to inconsistent results. Here we studied whether therapeutic trains of rTMS have detectable effects on individual spike pattern and/or frequency in patients suffering from focal epilepsy. Five patients with focal epilepsy underwent one session of rTMS online with EEG using a 6 Hz prime/1 Hz rTMS protocol (real and sham). The EEG was recorded continuously throughout the stimulation, and the epileptic spikes recorded immediately before (baseline) and after stimulation (sham and real) were subjected to further analysis. Number of spikes, spike-strength and spike-topography were examined. In two of the five patients, real TMS led to significant changes when compared to baseline and sham (decrease in spike-count in one patient, change in topography of the after-discharge in the other patient). Spike-count and topography remained unchanged the remaining patients. Overall, our results do not indicate a consistent effect of rTMS stimulation on interictal spike discharges, but speak in favor of a rather weak and individually variable immediate effect of rTMS on focal epileptic activity. The individuation of most effective stimulation patterns will be decisive for the future role of rTMS in epilepsies and needs to be determined in larger studies.