Clinical NeuroscienceA novel approach for monitoring writing interferences during navigated transcranial magnetic stimulation mappings of writing related cortical areas

•Proposed setup to be used with nTMS mappings of writing related cortical areas.•Pen for writing integrated into EMG of nTMS system was developed.•On-line monitoring of EMG and pen related activity from hand muscles during writing.•Application of chronometric TMS design and patterned protocol of rTMS.•Stopping and slowing during writing was elicited by mapping premotor cortices.

BackgroundIt has recently been shown that navigated repetitive transcranial magnetic stimulation (nTMS) is useful in preoperative neurosurgical mapping of motor and language brain areas. In TMS mapping of motor cortices the evoked responses can be quantitatively monitored by electromyographic (EMG) recordings. No such setup exists for monitoring of writing during nTMS mappings of writing related cortical areas.New methodWe present a novel approach for monitoring writing during nTMS mappings of motor writing related cortical areas.Comparison with existing method(s)To our best knowledge, this is the first demonstration of quantitative monitoring of motor evoked responses from hand by EMG, and of pen related activity during writing with our custom made pen, together with the application of chronometric TMS design and patterned protocol of rTMS.ResultsThe method was applied in four healthy subjects participating in writing during nTMS mapping of the premotor cortical area corresponding to BA 6 and close to the superior frontal sulcus. The results showed that stimulation impaired writing in all subjects. The corresponding spectra of measured signal related to writing movements was observed in the frequency band 0-20 Hz. Magnetic stimulation affected writing by suppressing normal writing frequency band.ConclusionThe proposed setup for monitoring of writing provides additional quantitative data for monitoring and the analysis of rTMS induced writing response modifications. The setup can be useful for investigation of neurophysiologic mechanisms of writing, for therapeutic effects of nTMS, and in preoperative mapping of language cortical areas in patients undergoing brain surgery.