title: Associations between clinical outcome and navigated transcranial magnetic stimulation characteristics in patients with motor-eloquent brain lesions: a combined navigated transcranial magnetic stimulation-diffusion tensor imaging fiber tracking approach.
abstract: OBJECTIVE Navigated transcranial magnetic stimulation (nTMS) and diffusion tensor imaging fiber tracking (DTI FT) based on nTMS data are increasingly used for preoperative planning and resection guidance in patients suffering from motor-eloquent brain tumors. The present study explores whether nTMS-based DTI FT can also be used for individual preoperative risk assessment regarding surgery-related motor impairment. METHODS Data derived from preoperative nTMS motor mapping and subsequent nTMS-based tractography in 86 patients were analyzed. All patients suffered from high-grade glioma (HGG), low-grade glioma (LGG), or intracranial metastasis (MET). In this context, nTMS-based DTI FT of the corticospinal tract (CST) was performed at a range of fractional anisotropy (FA) levels based on an individualized FA threshold ([FAT]; tracking with 50%, 75%, and 100% FAT), which was defined as the highest FA value allowing for visualization of fibers (100% FAT). Minimum lesion-to-CST distances were measured, and fiber numbers of the reconstructed CST were assessed. These data were then correlated with the preoperative, postoperative, and follow-up status of motor function and the resting motor threshold (rMT). RESULTS At certain FA levels, a statistically significant difference in lesion-to-CST distances was observed between patients with HGG who had no impairment and those who developed surgery-related transient or permanent motor deficits (75% FAT: p = 0.0149; 100% FAT: p = 0.0233). In this context, no patient with a lesion-to-CST distance ≥ 12 mm suffered from any new surgery-related permanent paresis (50% FAT and 75% FAT). Furthermore, comparatively strong negative correlations were observed between the rMT and lesion-to-CST distances of patients with surgery-related transient paresis (Spearman correlation coefficient [rs]; 50% FAT: rs= -0.8660; 75% FAT: rs= -0.8660) or surgery-related permanent paresis (50% FAT: rs= -0.7656; 75% FAT: rs= -0.6763). CONCLUSIONS This is one of the first studies to show a direct correlation between imaging, clinical status, and neurophysiological markers for the integrity of the motor system in patients with brain tumors. The findings suggest that nTMS-based DTI FT might be suitable for individual risk assessment in patients with HGG, in addition to being a surgery-planning tool. Importantly, necessary data for risk assessment were obtained without significant additional efforts, making this approach potentially valuable for direct clinical use.
authors.affiliation: 1Department of Neurosurgery.|2TUM-Neuroimaging Center, and.
authors.forename: Nico
authors.initials: N
authors.lastname: Sollmann
authors.affiliation: 1Department of Neurosurgery.|2TUM-Neuroimaging Center, and.
authors.forename: Noémie
authors.initials: N
authors.lastname: Wildschuetz
authors.affiliation: 1Department of Neurosurgery.|2TUM-Neuroimaging Center, and.
authors.forename: Anna
authors.initials: A
authors.lastname: Kelm
authors.affiliation: 1Department of Neurosurgery.|2TUM-Neuroimaging Center, and.
authors.forename: Neal
authors.initials: N
authors.lastname: Conway
authors.affiliation: 1Department of Neurosurgery.|2TUM-Neuroimaging Center, and.
authors.forename: Tobias
authors.initials: T
authors.lastname: Moser
authors.affiliation: 1Department of Neurosurgery.|2TUM-Neuroimaging Center, and.
authors.forename: Lucia
authors.initials: L
authors.lastname: Bulubas
authors.affiliation: 3Section of Neuroradiology, Department of Radiology, Klinikum rechts der Isar, Technische Universität München,Germany.
authors.forename: Jan S
authors.initials: JS
authors.lastname: Kirschke
authors.affiliation: 1Department of Neurosurgery.
authors.forename: Bernhard
authors.initials: B
authors.lastname: Meyer
authors.affiliation: 1Department of Neurosurgery.|2TUM-Neuroimaging Center, and.
authors.forename: Sandro M
authors.initials: SM
authors.lastname: Krieg
mesh_terms: D000328:Adult; D000368:Aged; D001921:Brain / Q000000981:diagnostic imaging* / Q000601:surgery; D001931:Brain Mapping / Q000379:methods*; D001932:Brain Neoplasms / Q000000981:diagnostic imaging* / Q000601:surgery; D056324:Diffusion Tensor Imaging; D005260:Female; D005910:Glioma / Q000000981:diagnostic imaging* / Q000601:surgery; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D038361:Neuronavigation; D011712:Pyramidal Tracts / Q000000981:diagnostic imaging*; D050781:Transcranial Magnetic Stimulation
keywords: BMRC = British Medical Research Council; CST = corticospinal tract; DTI, DTI FT = diffusion tensor imaging, DTI fiber tracking; FA, FAT = fractional anisotropy, FA threshold; HGG = high-grade glioma; IOM = intraoperative monitoring; LAD = lesion-to-activation distance; LGG = low-grade glioma; MEP = motor evoked potential; MET = metastasis; ROI = region of interest; brain tumor; corticospinal tract; diagnostic technique; diffusion tensor imaging; fMRI = functional MRI; nTMS = navigated transcranial magnetic stimulation; navigated transcranial magnetic stimulation; rMT = resting motor threshold; risk stratification; rs = Spearman correlation coefficient; tractography