Artikel
Confirming rTMS language mapping by preoperative rTMS-based fiber tracking and intraoperative stimulation
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Veröffentlicht: | 8. Juni 2016 |
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Gliederung
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Objective: Nowadays, intraoperative direct cortical stimulation (DCS) and preoperative mapping by repetitive navigated transcranial magnetic stimulation (rTMS) is used to localize cortical regions relevant for language function prior to brain tumor resections. In addition, rTMS-based diffusion tensor imaging fiber tracking (DTI FT) can be used for visualization of subcortical pathways. The aim of the present investigation was to evaluate specificity/sensitivity of rTMS language points confirmed by rTMS-based DTI FT compared to DCS.
Method: Twenty patients with left-sided language-eloquent brain lesions underwent rTMS language mapping prior to awake surgery. rTMS-based DTI FT was conducted subsequently with different fractional anisotropy thresholds (FATs: 100%, 75%, 50%, 25% FAT) and fiber lengths (FLs: 100mm, 70 mm, 40 mm) for the areas exposed by the craniotomy. rTMS language points that were confirmed by rTMS-based DTI FT were then compared to DCS-positive brain areas.
Results: Specificity was slightly better for anterior cortical regions, while sensitivity appeared to be higher in posterior regions. The best balanced result was achieved for 100% FAT/40 mm FL (sensitivity: 62.8%; specificity: 64.3%), whereas DTI FT with 25% FAT/40 mm FL led to a sensitivity of 100% and a negative predictive value (NPV) of 100%.
Conclusions: Depending strongly on tracking adjustments, the confirmation of rTMS-positive language areas by rTMS-based DTI FT seems to be characterized by specificity/sensitivity values comparable to those of cortical mapping. Further stimulation and tracking protocol refinements might improve these results.