gms | German Medical Science

Objective: Navigated transcranial magnetic stmulation (nTMS) has been used for studying language organization in healthy volunteers and patients to detect language areas as exactly as possible. However, still little is known about the reliability of this method. To determine whether the results obtained by nTMS show sufficient reliability, we conducted both an interobserver and an intraobserver investigation.

Method: Ten right-handed healthy subjects underwent nTMS for three times: mapping, first, and second remapping. At each point, the language mapping was performed by repetitive nTMS (5-7 Hz, 5-7 pulses, 300 ms delay) and the same object naming task. The induced speech impairment was categorized into six different error types. To evaluate intraobserver reliability, the first and the second mapping was conducted by the same investigator. Another investigator performed the third mapping to determine interobserver reliability. The time lag between mapping and first remapping was 191.4 ± 67.5 days) and 20.4 ± 9.6 days) between first and second remapping. Post-hoc analysis was performed blinded to the previous results.

Results: Over all, the results of both the interobserver and the intraobserver investigations show sufficient accordance. This is demonstrated by comparing the error rate of all different error types in total of both examinations. Considering the most important error type, “no response”, there is only small variability in inter- and intraobserver mapping.

Conclusions: Navigated TMS is a reliable technique to identify language related sites in healthy subjects. With our protocol, the results of interobserver studies correspond well, but not quite as good as those received by intraobserver studies. Despite small differences in inter- and intraobserver variabilty, nTMS is a promising method for preoperative planning as well as neuropsychological research.