title: Functional MRI vs. navigated TMS to optimize M1 seed volume delineation for DTI tractography. A prospective study in patients with brain tumours adjacent to the corticospinal tract.
abstract: DTI-based tractography is an increasingly important tool for planning brain surgery in patients suffering from brain tumours. However, there is an ongoing debate which tracking approaches yield the most valid results. Especially the use of functional localizer data such as navigated transcranial magnetic stimulation (nTMS) or functional magnetic resonance imaging (fMRI) seem to improve fibre tracking data in conditions where anatomical landmarks are less informative due to tumour-induced distortions of the gyral anatomy. We here compared which of the two localizer techniques yields more plausible results with respect to mapping different functional portions of the corticospinal tract (CST) in brain tumour patients.
  
  
  
  The CSTs of 18 patients with intracranial tumours in the vicinity of the primary motor area (M1) were investigated by means of deterministic DTI. The core zone of the tumour-adjacent hand, foot and/or tongue M1 representation served as cortical regions of interest (ROIs). M1 core zones were defined by both the nTMS hot-spots and the fMRI local activation maxima. In addition, for all patients, a subcortical ROI at the level of the inferior anterior pons was implemented into the tracking algorithm in order to improve the anatomical specificity of CST reconstructions. As intra-individual control, we additionally tracked the CST of the hand motor region of the unaffected, i.e., non-lesional hemisphere, again comparing fMRI and nTMS M1 seeds. The plausibility of the fMRI-ROI- vs. nTMS-ROI-based fibre trajectories was assessed by a-priori defined anatomical criteria. Moreover, the anatomical relationship of different fibre courses was compared regarding their distribution in the anterior-posterior direction as well as their location within the posterior limb of the internal capsule (PLIC).
  
  
  
  Overall, higher plausibility rates were observed for the use of nTMS- as compared to fMRI-defined cortical ROIs (p< 0.05) in tumour vicinity. On the non-lesional hemisphere, however, equally good plausibility rates (100%) were observed for both localizer techniques. fMRI-originated fibres generally followed a more posterior course relative to the nTMS-based tracts (p< 0.01) in both the lesional and non-lesional hemisphere.
  
  
  
  NTMS achieved better tracking results than fMRI in conditions when the cortical tract origin (M1) was located in close vicinity to a brain tumour, probably influencing neurovascular coupling. Hence, especially in situations with altered BOLD signal physiology, nTMS seems to be the method of choice in order to identify seed regions for CST mapping in patients.
authors.affiliation: University of Cologne, Center of Neurosurgery, 50924 Cologne, Germany.
authors.forename: Carolin
authors.initials: C
authors.lastname: Weiss Lucas
authors.affiliation: University of Cologne, Center of Neurosurgery, 50924 Cologne, Germany.
authors.forename: Irada
authors.initials: I
authors.lastname: Tursunova
authors.affiliation: University of Cologne, Center of Neurosurgery, 50924 Cologne, Germany.
authors.forename: Volker
authors.initials: V
authors.lastname: Neuschmelting
authors.affiliation: University of Cologne, Center of Neurosurgery, 50924 Cologne, Germany.
authors.forename: Charlotte
authors.initials: C
authors.lastname: Nettekoven
authors.affiliation: Institute of Neuroscience and Medicine, Research Centre Jülich, 52425 Jülich, Germany.
authors.forename: Ana-Maria
authors.initials: AM
authors.lastname: Oros-Peusquens
authors.affiliation: Institute of Neuroscience and Medicine, Research Centre Jülich, 52425 Jülich, Germany.
authors.forename: Gabriele
authors.initials: G
authors.lastname: Stoffels
authors.affiliation: University of Cologne, Center of Neurosurgery, 50924 Cologne, Germany.
authors.forename: Andrea Maria
authors.initials: AM
authors.lastname: Faymonville
authors.affiliation: Institute of Neuroscience and Medicine, Research Centre Jülich, 52425 Jülich, Germany; RWTH Aachen University, University Clinic Aachen, Departments of Nuclear Medicine and Neurology, 52074 Aachen, Germany; Department of Electrical and Computer Systems Engineering, Monash University, Melbourne, Victoria, Australia; Monash Institute of Medical Engineering, Monash University, Melbourne, Victoria, Australia; Monash Biomedical Imaging, School of Psychological Sciences, Monash University, Melbourne, Victoria, Australia.
authors.forename: Shah N
authors.initials: SN
authors.lastname: Jon
authors.affiliation: Institute of Neuroscience and Medicine, Research Centre Jülich, 52425 Jülich, Germany; RWTH Aachen University, University Clinic Aachen, Departments of Nuclear Medicine and Neurology, 52074 Aachen, Germany.
authors.forename: Karl Josef
authors.initials: KJ
authors.lastname: Langen
authors.affiliation: University of Cologne, Department of Radiology, 50937 Cologne, Germany.
authors.forename: Hannah
authors.initials: H
authors.lastname: Lockau
authors.affiliation: University of Cologne, Center of Neurosurgery, 50924 Cologne, Germany.
authors.forename: Roland
authors.initials: R
authors.lastname: Goldbrunner
authors.affiliation: Institute of Neuroscience and Medicine, Research Centre Jülich, 52425 Jülich, Germany; University of Cologne, Department of Neurology, 50924 Cologne, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Grefkes
mesh_terms: D000328:Adult; D000368:Aged; D001931:Brain Mapping / Q000379:methods / Q000592:standards*; D001932:Brain Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology / Q000503:physiopathology; D056324:Diffusion Tensor Imaging / Q000379:methods / Q000592:standards*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods / Q000592:standards*; D008297:Male; D008875:Middle Aged; D009044:Motor Cortex / Q000000981:diagnostic imaging* / Q000473:pathology / Q000503:physiopathology; D011712:Pyramidal Tracts / Q000000981:diagnostic imaging* / Q000473:pathology / Q000503:physiopathology; D050781:Transcranial Magnetic Stimulation / Q000379:methods / Q000592:standards*
keywords: APB, Abductor pollicis brevis muscle; BOLD, Blood-oxygenation-level dependent; CST; CST, Corticospinal tract; DCS, Direct cortical stimulation; DTI, Diffusion tensor imaging; Deterministic; EF, Electric field; EMG, Electromyography; FA(T), Fractional anisotropy (threshold); FACT, Fibre assignment by continuous tracking; FOV, Field-of-view; FWE, Family-wise error; KPS, Karnofsky performance scale; LT, Lateral tongue muscle, anterior third; M1, Primary motor cortex; MEP, Motor-evoked potential; MFL, Minimal fibre length; MPRAGE, Magnetization prepared rapid acquisition gradient echo (T1 MR seq.); OR, Odd's ratio; PLIC, Posterior limb of the internal capsule; PM, Plantar muscle; Pyramidal tract; RMT, Resting motor threshold; ROI; ROI, Region-of-interest; SD, Standard deviation; SE, Standard error; Somatotopic; X-sq, X-squared (Pearson's chi-square test); dMRI, Diffusion magnetic resonance imaging (i.e., diffusion-weighted imaging, DWI); fMRI; fMRI, Functional magnetic resonance imaging; nTMS; nTMS, Neuronavigated transcranial magnetic stimulation; pxsq, p-value according to Pearson's chi-square test