engleski

P143 Navigated transcranial magnetic stimulation of premotor cortex and long latency responses elicited in hand muscles during handwriting

Introduction The nTMS technique is often used in preoperative mapping of motor, speech and language related cortical areas in patients undergoing neurosurgical operation. Only few intraoperative studies investigated network underlying the production of written language and found that the superior premotor cortices close to the superior frontal sulcus was involved in handwritten production of words. The nTMS methodology for identification of the motor frontal areas involved in handwriting that can be used in preoperative mapping of patients is not yet established. Objectives To evaluate for the first time the feasibility of patterned rTMS protocol for locating premotor writing function in healthy volunteers. Materials & methods The ten healthy and right- handed volunteers (three female, and seven males, mean age 40.2 ± 11.17 (range 24–63 years) underwent rTMS of the left primary motor cortex (M1) and superior premotor cortices including the posterior part of superior and middle frontal gyri. Patterned bursts of rTMS consisted of 4 bursts of 4 stimuli each, with an interstimulus interval of 6 ms, and a burst repetition rate of 4 Hz were applied during writing to a dictation task and with EMG recording from right APB and FDI muscles. Two trains of these rTMS bursts were applied in a single trial, therefore after auditory presenting the sentence two rTMS trains (separated 2–7 s depending on the length of sentence) were given while the participant was writing with the pen. Results The rTMS of the left superior premotor cortex close to the superior frontal sulcus elicited long latency responses (LLRs) from the hand muscles with the latency of 70.72 ± 8.25 ms followed by MEPs (Fig. 1), as well as writing related disturbances (writing arrest, trembling, poor grapheme production, slow writing, lifting of the hand). Conclusion The application of rTMS to the premotor cortex close to superior frontal sulcus elicited writing interferences and LLR responses that were recorded in dominant hand muscle during writing. Further rTMS studies would be needed to clarify an exact neurophysiologic mechanism of LLR generation in hand muscles during voluntary writing task, as well as during different voluntary motor tasks. Although still preliminary, the results might have clinical value for preoperative use of rTMS in functional mapping of writing.

premotor cortex, long latency response, hand musles

DOI: http://dx.doi.org/10.1016/j.clinph.2016.10.265