Dear community,
does anyone of you have experience performing cortical facial nerve stimulation with TMS? If so, where do you stimulate? Any experiences with the (central) MEP conduction time in central facial paresis? I am looking forward to your suggestions!
The big trick with this MEP is to be able to differentiate between a MEP that has a central pathway and one that is extra-cranially generated. I use the latency of the two to separate them. WHen using TMS I orientate the coil roughly perpendicular to the skull. I place the coil slightly more frontal than the traditional M1 location. Good luck.
Dear Professor Norton,
thank you for the advice and for sharing your expertise.
We tried the cortical stimulation, evoking a very early potential (~ 3 ms latency) when recording from the M. orbicularis oris, M. buccinator or the nasalis. This MEP appeared even earlier than the one during canalicular stimulation (~ 2,5 ms latency) which we cannot attribute to any physiological process - do you have any idea what kind of potential we got during cortical TMS? - we actually do not think that we really record a cortical facial nerve MEP because it would be irrational that this appears earlier than the one during canalicular stimulation.
Looking forward to your comment(s)!
Dear Dr Modaber,
thank you for the comment. We ruled out this possibilty by changing the coil position and the potential we received just occured when we applied the stimulus over the assumed hot-spot (estimated by mapping APB muscle first, then going lateral); thats why we are still not clear about this potential. It also is for sure no artificial coil artifact because it changes its amplitude gradually until a stable reproducible level. I am looking forward to further comments!
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