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

Abstract

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.

Effect of low frequency repetitive transcranial magnetic stimulation on kindling-induced changes in electrophysiological properties of rat CA1 pyramidal neurons

“…Several studies have shown that after low frequency rTMS treatment in epileptic patients the number of interictal spikes on EEG decreases significantly (Brodbeck et al, 2010;Fregni et al, 2005;Joo et al, 2007;Menkes and Gruenthal, 2000;Santiago-Rodriguez et al, 2008) and this effect lasts approximately for two months (Misawa et al, 2005). The anticonvulsive action of rTMS has also been shown in laboratory animals (Akamatsu et al, 2001;Mongabadi et al, 2013;Tokay et al, 2009;Yadollahpour et al, 2014); however, a few studies have been done to determine the effect of rTMS on neuronal excitability.…”

Focal dystonia and the Sensory-Motor Integrative Loop for Enacting (SMILE)

“…Nevertheless, testing this type of hypothesis is particularly challenging using conventional neuroimaging or behavioral techniques, due to the difficulty of distinguishing between excitatory or inhibitory processes. In order to overcome this limitation transcranial magnetic stimulation (TMS) – a non-invasive technique allowing the excitation or inhibition of specific brain regions through magnetic pulses – has been largely used to study the properties of given cortico-spinal pathways (Miniussi and Thut, 2010) both in healthy and clinical populations (Brodbeck et al, 2010; Rotenberg, 2010). The features of the “motor-evoked potentials” (time-locked electromyographic activity resulting from a supra-threshold TMS pulse over the motor cortex) and cortical silent period (CSP; the interval of silent electromyographic activity following a supra-threshold TMS pulse) can provide information regarding the underlying state of the neural populations.…”

New Perspectives in Transcranial Magnetic Stimulation: Epilepsy, Consciousness and the Perturbational Approach

“…Yet, results from placebo-controlled trials are mixed, with one trial demonstrating a reduction in seizures and improvement of (off-line) EEG [107], and two others showing insignificant clinical improvement, or improvement of the EEG without a significant reduction in seizures [108][109][110]. Finally, Brodbeck et al [111] found no decrease in seizure frequency after rTMS [111]. Among the factors contributing to the inconsistent findings in antiepileptic rTMS trials may be the difficulty in selecting an appropriate intensity of extramotor TMS, i.e., stimulation output intensity outside the motor cortex.…”