title: Correlating subcortical interhemispheric connectivity and cortical hemispheric dominance in brain tumor patients: A repetitive navigated transcranial magnetic stimulation study.
abstract: OBJECTIVE
  The present study aims to investigate the relationship between transcallosal interhemispheric connectivity (IC) and hemispheric language lateralization by using a novel approach including repetitive navigated transcranial magnetic stimulation (rTMS), hemispheric dominance ratio (HDR) calculation, and rTMS-based diffusion tensor imaging fiber tracking (DTI FT).
  
  
  METHODS
  31 patients with left-sided perisylvian brain lesions underwent diffusion tensor imaging (DTI) and rTMS language mapping. Cortical language-positive rTMS spots were used to calculate HDRs (HDR: quotient of the left-sided divided by right-sided naming error rates for corresponding left- and right-sided cortical regions) and to create regions of interest (ROIs) for DTI FT. Then, fibers connecting the rTMS-based ROIs of both hemispheres were tracked, and the correlation of IC to HDRs was calculated via Spearman's rank correlation coefficient (rs).
  
  
  RESULTS
  Fibers connecting rTMS-based ROIs of both hemispheres were detected in 12 patients (38.7%). Within the patients in which IC was detected, the mean number of subcortical IC fibers ± standard deviation (SD) was 138.0 ± 346.5 (median: 7.5; range: 1-1,217 fibers). Regarding rs for the correlation of HDRs and fiber numbers of patients that showed IC, only moderate correlation was revealed.
  
  
  CONCLUSIONS
  Our approach might be beneficial and technically feasible for further investigation of the relationship between IC and language lateralization. However, only moderate correlation was revealed in the present study.
authors.affiliation: Department of Neurosurgery, Klinikum rechts der Isar, Technische Universität München, Germany; TUM-Neuroimaging Center, Klinikum rechts der Isar, Technische Universität München, Germany. Electronic address: Nico.Sollmann@tum.de.
authors.forename: Nico
authors.initials: N
authors.lastname: Sollmann
authors.affiliation: Department of Neurosurgery, Klinikum rechts der Isar, Technische Universität München, Germany; TUM-Neuroimaging Center, Klinikum rechts der Isar, Technische Universität München, Germany. Electronic address: Sebastian.Ille@tum.de.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Ille
authors.affiliation: Department of Neurosurgery, Klinikum rechts der Isar, Technische Universität München, Germany; TUM-Neuroimaging Center, Klinikum rechts der Isar, Technische Universität München, Germany. Electronic address: Tussislorena@gmail.com.
authors.forename: Lorena
authors.initials: L
authors.lastname: Tussis
authors.affiliation: Department of Neurosurgery, Klinikum rechts der Isar, Technische Universität München, Germany; TUM-Neuroimaging Center, Klinikum rechts der Isar, Technische Universität München, Germany. Electronic address: S.Maurer@tum.de.
authors.forename: Stefanie
authors.initials: S
authors.lastname: Maurer
authors.affiliation: Department of Neurosurgery, Klinikum rechts der Isar, Technische Universität München, Germany; TUM-Neuroimaging Center, Klinikum rechts der Isar, Technische Universität München, Germany. Electronic address: Thehauck@googlemail.com.
authors.forename: Theresa
authors.initials: T
authors.lastname: Hauck
authors.affiliation: Department of Neurosurgery, Klinikum rechts der Isar, Technische Universität München, Germany; TUM-Neuroimaging Center, Klinikum rechts der Isar, Technische Universität München, Germany. Electronic address: Chiara.Negwer@tum.de.
authors.forename: Chiara
authors.initials: C
authors.lastname: Negwer
authors.affiliation: Section of Neuroradiology, Department of Radiology, Klinikum rechts der Isar, Technische Universität München, Germany. Electronic address: Jsb@tum.de.
authors.forename: Jan S
authors.initials: JS
authors.lastname: Bauer
authors.affiliation: Department of Neurosurgery, Klinikum rechts der Isar, Technische Universität München, Germany. Electronic address: Florian.Ringel@tum.de.
authors.forename: Florian
authors.initials: F
authors.lastname: Ringel
authors.affiliation: Department of Neurosurgery, Klinikum rechts der Isar, Technische Universität München, Germany. Electronic address: Bernhard.Meyer@tum.de.
authors.forename: Bernhard
authors.initials: B
authors.lastname: Meyer
authors.affiliation: Department of Neurosurgery, Klinikum rechts der Isar, Technische Universität München, Germany; TUM-Neuroimaging Center, Klinikum rechts der Isar, Technische Universität München, Germany. Electronic address: Sandro.Krieg@tum.de.
authors.forename: Sandro M
authors.initials: SM
authors.lastname: Krieg
mesh_terms: D000328:Adult; D001932:Brain Neoplasms / Q000175:diagnosis / Q000378:metabolism*; D002540:Cerebral Cortex / Q000378:metabolism* / Q000473:pathology; D056324:Diffusion Tensor Imaging / Q000379:methods*; D005260:Female; D007839:Functional Laterality / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009415:Nerve Net / Q000378:metabolism* / Q000473:pathology; D050781:Transcranial Magnetic Stimulation / Q000379:methods*; D055815:Young Adult
keywords: Diffusion tensor imaging; Fiber tracking; Hemispheric dominance; Language; Object naming; Transcranial magnetic stimulation