Artikel
Fibre tracking from DCS positive language spots during awake surgeries reveals error-dependent connectivity patterns
Fibertracking von DCS positiven Sprachpunkten während Wachkraniotomien macht fehlerqualitätabhängige Konnektivitätsmuster deutlich
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Veröffentlicht: | 26. Juni 2020 |
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Objective: Little is known about the functional neuroanatomy of language. Currently, a hodotopic concept of language is propagated that draws the focus to subcortical fiber connections. 5 relevant fiber tracts have been assigned to the processing of language: the Superior Longitudinal Fasciculus/ Arcuate Fasciculus (AF), the Inferior Longitudinal Fasciculus (ILF), the Inferior Fronto-Occipital Fasciculus (IFOF), the Frontal Aslant Tract (FAT) and the Uncinate Fasciculus (UC). Cortical and subcortical mapping is used as the gold standard to define functional resection boundaries in language eloquent areas. Our aim was to investigate the functional connectivity of language positive spots during awake surgeries.
Methods: 13 patients with brain tumors in speech-related areas were evaluated with direct cortical stimulation (DCS, 50Hz, 6-8 mA, 200µs pulse width) and subcortical stimulation during awake surgeries, employing a picture-naming task. Preoperatively, they all received an MRI with MP-RAGE and DTI sequences. Positive and negative stimulation spots within the craniotomy were documented in the same MRI data set with respect to the linguistic quality of the error. The spots were converted into tract seeding points for DTI fibertracking, using a fractional anisotropy of 80% of the respective threshold value. Emerging fibers were analyzed with respect to their integration into well-established language tracts
Results: Altogether, 61 cortical and 15 subcortical language positive spots were documented. 32 integrated into FA, 21 to IFOF, 6 to FAT, 6 into association fibers, 9 into commissural fibers, 2 to the parasagittal parietal cortical region. The majority (62%) of cortical spots connecting into AF originated in the pars opercularis of the frontal operculum. All speech errors within the supramarginal gyrus connected into AF. The majority (87%) of spots connecting to IFOF originated in the dorsal part of the superior and middle temporal gyrus. All speech errors within the pars triangularis of the frontal operculum integrated into FAT. No cortical speech eloquent spots integrated into UF or ILF.
The main speech error integrating into FA was anomia. The main speech error integrating into IFOF was semantic. 100% of speech errors integrating into FAT were semantic.
Conclusion: Fibertracking from speech eloquent areas may help allocate subfunctions to the fiber tracts that implement speech in the human brain, and may thus contribute to solving the cortico-subcortical connectivity patterns of language.