Diffusion imaging and transcranial magnetic stimulation assessment of transcallosal pathways in chronic stroke

Clin Neurophysiol. 2015 Oct;126(10):1959-71. doi: 10.1016/j.clinph.2014.12.018. Epub 2015 Jan 12.

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.

Significance: 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.

Keywords: Diffusion imaging; Motor function; Motor impairment; Stroke; Transcallosal inhibition; Transcranial magnetic stimulation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aged
  • Aged, 80 and over
  • Chronic Disease
  • Corpus Callosum / metabolism
  • Corpus Callosum / pathology*
  • Diffusion Magnetic Resonance Imaging / methods*
  • Female
  • Humans
  • Male
  • Middle Aged
  • Prefrontal Cortex / metabolism
  • Prefrontal Cortex / pathology*
  • Stroke / diagnosis*
  • Stroke / metabolism
  • Transcranial Magnetic Stimulation / methods*