P07-S Multimodal TMS has the potential to improve the diagnostic process in epilepsy

Abstract

Background In epilepsy, a disturbed cortical excitability results in a predisposition to generate seizures. The limited diagnostic sensitivity of the electroencephalogram motivates the search for a novel biomarker. Transcranial magnetic stimulation (TMS) is a technique to assess cortical excitability. We used a multimodal TMS approach to evaluate differences between healthy controls, first seizure patients diagnosed with epilepsy and those without epilepsy. Methods We included twenty-one healthy subjects and twenty-one first seizure patients, of which seven were diagnosed with epilepsy. Both motor cortices were stimulated with 50 single pulses and 50 paired pulses at six interstimulus intervals (ISIs) between 50–300 As single pulse TMS readouts we analyzed amplitudes of the motor evoked potential (MEP) and TMS evoked potential (TEP). For paired pulse stimulation, we assessed long intracortical inhibition (LICI) of the MEP and TEP. Results We found no significant differences in MEP or TEP amplitudes using single pulse TCompared to healthy controls, epilepsy patients showed significantly increased LICI of the N100 and P180 components for ISI 200 Furthermore, we found facilitation at ISI 100 ms in epilepsy patients and inhibition in patients without epilepsy. Conclusions Multimodal TMS has the potential to improve the diagnostic process in epilepsy. Biomarkers include increased LICI at ISI 200 ms and facilitation at ISI 100 At a group level, paired pulse TMS differentiated between healthy controls, patients with epilepsy and patients without epilepsy. To establish the true potential, data of more patients is needed, which may enable analysis at the individual level.