Feasibility of nTMS-based DTI fiber tracking of language pathways in neurosurgical patients using a fractional anisotropy threshold

• Published in: Journal of neuroscience methods 2016-07, Vol.267, p.45-54
• Main Authors: Sollmann, Nico, Negwer, Chiara, Ille, Sebastian, Maurer, Stefanie, Hauck, Theresa, Kirschke, Jan S., Ringel, Florian, Meyer, Bernhard, Krieg, Sandro M.
• Format: Article
• Language: English
• Subjects: Adult; Brain - diagnostic imaging; Brain - physiopathology; Brain - surgery; Brain Mapping - methods; Brain Neoplasms - diagnostic imaging; Brain Neoplasms - physiopathology; Brain Neoplasms - surgery; Cortical mapping; Diffusion tensor imaging; Diffusion Tensor Imaging - methods; Feasibility Studies; Female; Fiber tracking; Humans; Imaging, Three-Dimensional - methods; Intracranial Arteriovenous Malformations - diagnostic imaging; Intracranial Arteriovenous Malformations - physiopathology; Intracranial Arteriovenous Malformations - surgery; Language; Male; Middle Aged; Neural Pathways - diagnostic imaging; Neural Pathways - physiopathology; Neural Pathways - surgery; Neurosurgical Procedures; Transcranial magnetic stimulation; Transcranial Magnetic Stimulation - methods; White Matter - diagnostic imaging; White Matter - physiopathology; White Matter - surgery; Young Adult
• ISSN: 0165-0270; 1872-678X
• DOI: 10.1016/j.jneumeth.2016.04.002

•nTMS maps can be used for DTI FT of subcortical language pathways.•Language pathways are detectable with nTMS spots as ROI.•25% and 50% FAT allow for most favorable DTI FT of language pathways. Navigated transcranial magnetic stimulation (nTMS) provides language maps in brain tumor patients. Yet, corresponding data on the visualization of language-related subcortical pathways is lacking. Therefore, this study evaluates the feasibility of nTMS-based diffusion tensor imaging fiber tracking (DTI FT) for subcortical language pathways by a fractional anisotropy (FA) protocol. DTI FT was performed in 37 patients suffering from left-sided perisylvian brain lesions based on nTMS data exclusively, using the FA-based protocol originally established for the corticospinal tract (CST) by Frey et al. (2012): minimum fiber length was 110mm and the highest individual FA value leading to visualization of white matter tracts was determined as the FA threshold (FAT). Then, deterministic DTI FT using an FA value of 100%, 75%, 50%, and 25% of the individual FAT (with 25% as an additional setting to the original protocol) was performed. Our approach visualized 9 language-related subcortical white matter pathways. By using 100% FAT, the mean percentage of visualized tracts was 13.5%, whereas DTI FT performed with 75%, 50%, and 25% FAT detected 30.6%, 61.3%, and 93.7% of language-related fiber tracts, respectively. nTMS language mapping alone is not able to visualize subcortical language-related pathways. This study shows that nTMS language maps are feasible for DTI FT of language-related pathways within the scope of a FAT-based protocol. Although this approach is novel and might be helpful during scientific neuroimaging and tumor resection, intraoperative validation is needed to go beyond the level of feasibility.