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Robotized TMS-EEG in Epilepsy

Robotized TMS-EEG in Epilepsy

By Esther Ter Braack

Epilepsy is characterized by an increased likelihood for seizures, and the EEG is an important tool in the diagnostic process and classification of the various epilepsy syndromes. However, routine EEGs shows epileptiform abnormalities in only 30-50% of the patients clinically diagnosed with epilepsy. Epilepsy is characterized by an increase in excitability. Because transcranial magnetic stimulation (TMS) can be used to measure excitability, it is a promising technique for epilepsy research. When TMS is applied while recording EEG, a characteristic waveform - the TMS evoked potential - is induced in the EEG.

We recorded TMS/EEG in healthy controls and adult patients with epilepsy to study TMS evoked potentials. At present, 18 healthy subjects and 10 epilepsy patients have been included. TMS/EEG was recorded using a Magstim Rapid2 stimulator and a 64-channel EEG amplifier (ANT neuro, Enschede). We administered single pulses at an intensity of 110% motor threshold at different targets. The TMS evoked potential was obtained by averaging over all TMS pulses for a specific target. Currently, we are analyzing the recorded data to investigate whether epilepsy patients show different responses to TMS than healthy volunteers.

We use smartmove to position the TMS coil, using the subject`s individual MRI scan. The smartmove system enables us to stimulate a specific TMS target for several minutes, without the need to continuously track whether the coil is still at the right location. In addition, the system positions the coil at the target automatically. After some practice, setting up an experiment without preparing the EEG cap takes us about 15 minutes.

With our research, we hope to demonstrate that epilepsy patients show different TMS evoked responses than healthy volunteers. Hopefully, TMS can be used in the future as an additional tool to diagnose epilepsy and monitor the response to anti-epileptic drugs.    

Researchers: Esther M. Ter Braack MSc, Michel J.A.M. Van Putten MD PhD
Department: Clinical Neurophysiology
Institution: University of Twente & Medisch Spectrum Twente, Enschede

About Esther ter Braack

Esther M. Ter Braack MSc, is a PhD student working in the department of Clinical Neurophysiology at the University of Twente. Under supervision of Prof. Van Putten she is currently studying clinical applications of robot-assisted TMS.    

About smartmove

smartmove is a system based on a robot arm which in combination with the high accuracy optical tracking system allows planning of a complete stimulation session ahead by defining stimulation sites based on anatomical MRI information and functional information like fMRI, PET or EEG/MEG. The flexible design of the system offers researchers the ability to expand the application areas and for example use it together with an EEG acquisition system (asalab) for combined EEG-TMS studies.

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We would like to thank the team of Prof. Van Putten for their support of ANT products.

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