Improving the efficacy and reliability of rTMS language mapping by increasing the stimulation frequency

• Published in: Human brain mapping Vol. 42; no. 16; pp. 5309 - 5321
• Main Authors: Nettekoven, Charlotte, Pieczewski, Julia, Neuschmelting, Volker, Jonas, Kristina, Goldbrunner, Roland, Grefkes, Christian, Weiss Lucas, Carolin
• Format: Journal Article
• Language: English
• Published: Hoboken, USA John Wiley & Sons, Inc 01.11.2021
• Subjects: brain stimulation; Correlation coefficient; Correlation coefficients; Discomfort; Electric fields; error rate; Errors; Hemispheric laterality; Language; Mapping; noninvasive; pain; picture naming; Reliability; speech mapping; Stimulation; TMS; tolerability; Transcranial magnetic stimulation; Variance analysis; virtual lesion; brain stimulation; pain; noninvasive; error rate; tolerability; virtual lesion; speech mapping; TMS; picture naming
• ISSN: 1065-9471; 1097-0193; 1097-0193
• DOI: 10.1002/hbm.25619

Repetitive TMS (rTMS) with a frequency of 5–10 Hz is widely used for language mapping. However, it may be accompanied by discomfort and is limited in the number and reliability of evoked language errors. We, here, systematically tested the influence of different stimulation frequencies (i.e., 10, 30, and 50 Hz) on tolerability, number, reliability, and cortical distribution of language errors aiming at improved language mapping. 15 right‐handed, healthy subjects (m = 8, median age: 29 yrs) were investigated in two sessions, separated by 2–5 days. In each session, 10, 30, and 50 Hz rTMS were applied over the left hemisphere in a randomized order during a picture naming task. Overall, 30 Hz rTMS evoked significantly more errors (20 ± 12%) compared to 50 Hz (12 ± 8%; p <.01), whereas error rates were comparable between 30/50 and 10 Hz (18 ± 11%). Across all conditions, a significantly higher error rate was found in Session 1 (19 ± 13%) compared to Session 2 (13 ± 7%, p <.05). The error rate was poorly reliable between sessions for 10 (intraclass correlation coefficient, ICC = .315) and 30 Hz (ICC = .427), whereas 50 Hz showed a moderate reliability (ICC = .597). Spatial reliability of language errors was low to moderate with a tendency toward increased reliability for higher frequencies, for example, within frontal regions. Compared to 10 Hz, both, 30 and 50 Hz were rated as less painful. Taken together, our data favor the use of rTMS‐protocols employing higher frequencies for evoking language errors reliably and with reduced discomfort, depending on the region of interest. The use of repetitive transcranial magnetic stimulation (rTMS) for language mapping is still hampered by a limited sensitivity and specificity, by an overall poor reliability and by stimulation‐associated discomfort. We, here, found that increasing the stimulation intensity up to 30 and 50 Hz can improve language mapping results as compared to the most commonly used protocol of 10 Hz rTMS.