Cortical Excitability Changes Induced by Retigabine: a Transcranial Magnetic Stimulation Study

Epilepsy is a disorder of brain excitability. Antiepileptic drugs (AEDs) modulate this excitability and transcranial magnetic stimulation (TMS) imposed itself as one of the best noninvasive methods to study cortical excitability in human subjects. Based on several recent studies, we hypothesize that measuring TMS parameters in the patients suffering from epilepsy can rapidly predict the effectiveness of the newly given AED and, ultimately, guide the optimization of the AED therapy. Characterizing the neurophysiological properties of innovative AEDs such as retigabine with TMS will allow 1) to better understand how AEDs modulate, in vivo, cortical excitability in humans in relation to their mode of action and 2) to establish TMS as a tool for assessing individual responsiveness to a particular AED treatment and for antiepileptic treatment monitoring. The effects of most AEDs on cortical excitability have been investigated. The modifications of the excitability parameters are related to the specific mode of action of each AED. For the new AED retigabine, at least two modes of action are known: 1) increase in cellular potassium efflux by changing conformation of the KV7.2-7.3 channels and 2) enhancement of GABA-A activity.