Article
Associations between clinical outcome and tractography based on navigated transcranial magnetic stimulation in patients with language-eloquent brain lesions
Zusammenhang zwischen klinischem Outcome und auf navigierter transkranieller Magnetstimulation basierender Traktographie bei Patienten mit spracheloquenten Hirntumoren
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Published: | May 8, 2019 |
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Objective: Navigated transcranial magnetic stimulation (nTMS) in combination with diffusion tensor imaging fiber tracking (DTI FT) is progressively used. The aim of this study is to establish nTMS-based DTI FT for preoperative risk stratification by evaluating associations between lesion-to-tract distances (LTDs) and aphasia.
Methods: Fifty patients with left-hemispheric, language-eloquent brain tumors underwent preoperative nTMS language mapping and nTMS-based DTI FT, followed by tumor resection. nTMS-based DTI FT was performed with a predefined fractional anisotropy (FA) of 0.10, 0.15, 50% of the individual FA threshold (FAT), and 75% FAT (minimum fiber length [FL]: 100 mm). The arcuate fascicle (AF), superior longitudinal fascicle (SLF), inferior longitudinal fascicle (ILF), uncinate fascicle (UC), and frontooccipital fascicle (FoF) were identified in nTMS-based tractography, and minimum LTDs were measured between the lesion and the AF and between the lesion and the closest other subcortical language-related pathway (either SLF, ILF, UC, or FoF). LTDs were then associated with the level of aphasia (no/transient or permanent surgery-related aphasia according to follow-up examinations).
Results: A significant difference in LTDs was observed between patients with no or only surgery-related transient impairment and those who developed surgery-related permanent aphasia with regards to the AF (FA=0.10: p=0.0321, FA=0.15: p=0.0143, FA=50% FAT: p=0.0106) as well as the closest other subcortical language-related pathway (FA=0.10: p=0.0182, FA=0.15: p=0.0200, FA=50% FAT: p=0.0077). Patients with surgery-related permanent aphasia showed the lowest LTDs in relation to these tracts. Thus, LTDs of ≥8 mm (AF) and ≥11 mm (either SLF, ILF, UC, or FoF) were determined as cut-off values for surgery-related permanent aphasia.
Conclusion: nTMS-based DTI FT of subcortical language-related pathways seems suitable for risk stratification and prediction in patients suffering from language-eloquent brain tumors. Thus, the current role of nTMS-based DTI FT might be expanded, going beyond the level of being a mere tool for surgical planning and resection guidance.