Artikel
Retest-reliability and tolerability of 10, 30 and 50 Hz repetitive transcranial magnetic stimulation (rTMS) for language mapping: a preclinical study
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Veröffentlicht: | 8. Juni 2016 |
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Gliederung
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Objective: Navigated repetitive transcranial stimulation (rTMS) represents a rather novel approach to depict highly language-relevant cortical sites non-invasively. Due to low specificity and considerable painfulness when stimulating with the commonly used 5-10 Hz rTMS, rTMS-language-mapping is still limited in its clinical use. In order to define a better tolerable protocol, we compared 5-10 Hz with higher-frequency rTMS regimes regarding discomfort/pain, test-retest reliability, rate and site of distinct evoked language errors.
Method: 13 right-handed, healthy subjects were investigated in 3 sessions (spaced by 2-5 d / 21-40 d). 10 Hz, 30 Hz and 50 Hz rTMS were applied over the left hemisphere, continuously covering facial (pre-)motor and language-related cortical areas. After defining the „motor inhibition threshold“ (MIT) which mirrors the efficacy of cortical inhibition, online-rTMS was applied during a picture-naming task in a randomized sequence. Evoked language errors (ELE) were rated by two independent raters using post-hoc video analysis according to a-priori defined error categories. At the end of each exam, the volunteers were asked to rate the mean and maximum level of discomfort on a 0-10 numeric rating scale (NRS).
Results: Better tolerability was observed for the 30 & 50 Hz rTMS protocols than for 10 Hz rTMS. Moreover, 30 and 50 Hz rTMS reliably evoked tongue movement disruption (Intraclass correlation coeff. = 0.65) at lower stimulation intensities compared to 10 Hz rTMS (p<0.01). Regarding ELE, the interrater reliability was good (Cohen’s kappa = 0.7). The rates of ELE did not differ between 10 and 30 Hz rTMS. However, lower ELE rates were observed for the 50 Hz rTMS as compared to 10 and 30 Hz for speech motor deficits, hesitations and phonemic paraphasias (p<0.05). Spatial reliability of ELE was generally low, showing considerable variability across subjects and error categories.
Conclusions: Higher-frequency rTMS (30/50 Hz) may enable cortical inhibition at a more favourable pain-effect ratio than 10 Hz rTMS. Despite good test-retest reliability of the event rates, the low spatial reliability of ELE requires critical discussion.