Article
Mapping cortical language regions using paired-pulse TMS – a proof-of-principle study
Kartierung kortikaler Sprachareale mittels Doppelpuls-TMS – eine Proof-of-Principle Studie
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Published: | June 4, 2021 |
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Objective: Assessing the cortical representation of language in the individual patient, e.g. by means of repetitive transcranial magnetic stimulation (rTMS), is of high importance in the preoperative context. We could recently show that rTMS with a frequency of 30 Hz is superior to the most commonly used protocol of (5-)10 Hz. Nevertheless, the still relatively low number of evoked language errors and the discomfort evoked by the stimulation drive the need for a further improved stimulation protocol. We, therefore, tested whether paired pulse (pp-)TMS is also suitable for inducing language errors.
Methods: 13 healthy, right-handed subjects (f=6, 25-41 years) were investigated using two different rTMS protocols: (i) the 30 Hz rTMS as control and (ii) the novel pp-TMS (interstimulus-interval: 7 ms). TMS protocols were applied in a pseudo-randomized order during a picture naming task (picture-to-trigger interval: 0 ms) over cortical language areas. Language errors were post-hoc analysed by two independent raters and were assigned to eight different error categories. The level of pain was assessed on a subjective 0-10 numeric rating scale (NRS).
Results: 30 Hz rTMS evoked a significantly higher number of errors than the pp-protocol, i.e., 18 ± 12 % vs. 10 ± 7 % (p<0.05). However, pp-TMS was significantly better tolerated with a mean NRS of 2.3 ± 1.6 vs. 3.4 ± 1.5 (p<0.05, FDR-corrected). Of note, pp-TMS evoked a higher number of anomias (15 ± 15 %) than 30 Hz rTMS (4 ± 7 %; p<0.1, FDR-corrected).
Conclusion: We could show that single pp-TMS is capable of inducing language errors whilst being well-tolerated by the subjects. Therefore, pp-TMS might be an alternative protocol for language mapping, also when considering safety aspects (lower total amount of electric current). Nevertheless, the pp-TMS protocol need to be further evaluated to optimize its potential use in preoperative language mapping.