title: Diffusion imaging and transcranial magnetic stimulation assessment of transcallosal pathways in chronic stroke.
abstract: OBJECTIVE
  To examine the relationship of transcallosal pathway microstructure and transcallosal inhibition (TCI) with motor function and impairment in chronic stroke.
  
  
  METHODS
  Diffusion-weighted magnetic resonance imaging and transcranial magnetic stimulation (TMS) data were collected from 24 participants with chronic stroke and 11 healthy older individuals. Post-stroke motor function (Wolf Motor Function Test) and level of motor impairment (Fugl-Meyer score) were evaluated.
  
  
  RESULTS
  Fractional anisotropy (FA) of transcallosal tracts between prefrontal cortices and the mean amplitude decrease in muscle activity during the ipsilateral silent period evoked by TMS over the non-lesioned hemisphere (termed NL-iSPmean) were significantly associated with level of motor impairment and motor function after stroke (p<0.05). A regression model including age, post-stroke duration, lesion volume, lesioned corticospinal tract FA, transcallosal prefrontal tract FA and NL-iSPmean accounted for 84% of variance in motor impairment (p<0.01). Both transcallosal prefrontal tract FA (ΔR(2)=0.12, p=0.04) and NL-iSPmean (ΔR(2)=0.09, p=0.04) accounted for unique variance in motor impairment level.
  
  
  CONCLUSIONS
  Prefrontal transcallosal tract microstructure and TCI are each uniquely associated with motor impairment in chronic stroke.
  
  
  CONCLUSIONS
  Utilizing a multi-modal approach to assess transcallosal pathways may improve our capacity to identify important neural substrates of motor impairment in the chronic phase of stroke.
authors: Graduate Program in Rehabilitation Sciences, Faculty of Medicine, University of British Columbia, Vancouver, Canada.
authors: Cameron S
authors: CS
authors: Mang
authors: Division of Physical Therapy, School of Medicine, Emory University, Atlanta, USA.
authors: Michael R
authors: MR
authors: Borich
authors: Graduate Program in Neuroscience, Faculty of Medicine, University of British Columbia, Vancouver, Canada.
authors: Sonia M
authors: SM
authors: Brodie
authors: Graduate Program in Rehabilitation Sciences, Faculty of Medicine, University of British Columbia, Vancouver, Canada.
authors: Katlyn E
authors: KE
authors: Brown
authors: Graduate Program in Rehabilitation Sciences, Faculty of Medicine, University of British Columbia, Vancouver, Canada.
authors: Nicholas J
authors: NJ
authors: Snow
authors: Graduate Program in Rehabilitation Sciences, Faculty of Medicine, University of British Columbia, Vancouver, Canada.
authors: Katie P
authors: KP
authors: Wadden
authors: Graduate Program in Rehabilitation Sciences, Faculty of Medicine, University of British Columbia, Vancouver, Canada; Graduate Program in Neuroscience, Faculty of Medicine, University of British Columbia, Vancouver, Canada. Electronic address: lara.boyd@ubc.ca.
authors: Lara A
authors: LA
authors: Boyd
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D002908:Chronic Disease; D003337:Corpus Callosum / Q000378:metabolism / Q000473:pathology*; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D017397:Prefrontal Cortex / Q000378:metabolism / Q000473:pathology*; D020521:Stroke / Q000175:diagnosis* / Q000378:metabolism; D050781:Transcranial Magnetic Stimulation / Q000379:methods*
keywords: Diffusion imaging; Motor function; Motor impairment; Stroke; Transcallosal inhibition; Transcranial magnetic stimulation