title: Changes in callosal motor fiber integrity after subcortical stroke of the pyramidal tract.
abstract: In the healthy brain, there are close correlations between task-related activation of the primary motor cortex (M1), the magnitude of interhemispheric inhibition, and microstructural properties of transcallosal fiber tracts. After subcortical stroke affecting the pyramidal tract (PT), an abnormal pattern of bilateral activity develops in M1. With this prospective longitudinal study, we aimed to determine whether a morphological correlate of poststroke disinhibition could be measured within 20 days and 6 months of PT stroke. Using diffusion tensor imaging with tractography, we delineated transcallosal motor fibers (CMF) in nine PT stroke patients, six patients with subcortical infarct not affecting the PT (NonPT) and six transient ischemic attack patients. We compared changes in CMF fractional anisotropy ratios (rFA) with rFA in a distinct bundle of callosal occipital fibers (COF). At the initial time point, there were no significant differences in rFA between groups and fiber bundles. At follow-up, PT-group rFA(CMF) was significantly lower than PT-group rFA(COF) and NonPT-group rFA(CMF). PT-group rFA(CMF) decreased over time and correlated with rFA of the PT (rFA(PT)) retrograde to the infarct at 6 months. Our data suggest a progressive degenerative transsynaptic effect of PT stroke on CMF, which could be a morphological correlate of transcallosal disinhibition.
authors.affiliation: Department of Neurology and Neurosurgery, Montréal Neurological Institute, Montréal, Quebec, Canada.
authors.forename: Basia A
authors.initials: BA
authors.lastname: Radlinska
authors.forename: Yasmin
authors.initials: Y
authors.lastname: Blunk
authors.forename: Ilana R
authors.initials: IR
authors.lastname: Leppert
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Minuk
authors.forename: G Bruce
authors.initials: GB
authors.lastname: Pike
authors.forename: Alexander
authors.initials: A
authors.lastname: Thiel
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016880:Anisotropy; D001931:Brain Mapping; D002544:Cerebral Infarction / Q000473:pathology*; D003337:Corpus Callosum / Q000473:pathology*; D056324:Diffusion Tensor Imaging; D005260:Female; D007839:Functional Laterality; D006801:Humans; D002546:Ischemic Attack, Transient / Q000473:pathology; D008137:Longitudinal Studies; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009044:Motor Cortex / Q000473:pathology*; D011446:Prospective Studies; D011712:Pyramidal Tracts / Q000473:pathology*; D012720:Severity of Illness Index