ORCID Profile
0000-0002-8211-9923
Current Organisations
University of Montreal
,
Institut universitaire de gériatrie de Montréal
,
University of British Columbia
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Publisher: Elsevier BV
Date: 09-2017
DOI: 10.1016/J.NEULET.2017.08.036
Abstract: Combining structural and functional magnetic resonance imaging may provide insight into how residual motor networks contribute to motor outcomes post-stroke. The purpose of this study was to examine whether a structural motor network (SMN), generated with fMRI guided diffusion-based tractography, relates to motor function post-stroke. Twenty-seven in iduals with mild to moderate upper limb impairment post stroke underwent diffusion magnetic resonance imaging. A bilateral motor network mask guided white matter tractography for each participant. Fractional anisotrophy (FA) was calculated for the SMN and corticospinal tracts (CST). The Wolf Motor Function Test (WMFT) rate and Fugl-Meyer Upper Limb (FM) tests characterized arm function and impairment respectively. The SMN and ipsilesional CST together explained approximately 35% of the variance in paretic arm function (WMFT-rate p=0.006). This study demonstrates that a broader motor network, like the SMN, is functionally meaningful. Given that the motor network is widely distributed, the proposed SMN warrants further investigation as a potential adjunct biomarker to characterize recovery potential after stroke.
Publisher: Hindawi Limited
Date: 2017
DOI: 10.1155/2017/4281532
Abstract: Background . Severity of arm impairment alone does not explain motor outcomes in people with severe impairment post stroke. Objective . Define the contribution of brain biomarkers to upper limb motor outcomes in people with severe arm impairment post stroke. Methods . Paretic arm impairment (Fugl-Meyer upper limb, FM-UL) and function (Wolf Motor Function Test rate, WMFT-rate) were measured in 15 in iduals with severe (FM-UL ≤ 30/66) and 14 with mild–moderate (FM-UL 40/66) impairment. Transcranial magnetic stimulation and diffusion weight imaging indexed structure and function of the corticospinal tract and corpus callosum. Separate models of the relationship between possible biomarkers and motor outcomes at a single chronic (≥6 months) time point post stroke were performed. Results . Age (Δ R 2 0.365, p = 0.017 ) and ipsilesional-transcallosal inhibition (Δ R 2 0.182, p = 0.048 ) explained a 54.7% ( p = 0.009 ) variance in paretic WMFT-rate. Prefrontal corpus callous fractional anisotropy (PF-CC FA) alone explained 49.3% ( p = 0.007 ) variance in FM-UL outcome. The same models did not explain significant variance in mild–moderate stroke. In the severe group, k-means cluster analysis of PF-CC FA distinguished two subgroups, separated by a clinically meaningful and significant difference in motor impairment ( p = 0.049 ) and function ( p = 0.006 ) outcomes. Conclusion . Corpus callosum function and structure were identified as possible biomarkers of motor outcome in people with chronic and severe arm impairment.
Publisher: Elsevier BV
Date: 05-2018
DOI: 10.1016/J.JNEUMETH.2018.03.001
Abstract: Information about the structural integrity of the corticospinal tract (CST) from diffusion-weighted imaging can improve our ability to understand motor outcomes in people with upper limb impairment after stroke, especially those with severe impairment. Yet, there is no consensus on which method of CST generation most accurately represents function and impairment in in iduals with chronic stroke. The aim of the study was to compare different methods of CST reconstruction and resulting microstructural properties, as well as the relationship between these properties and motor function and impairment. Fifteen in iduals with mild-moderate impairment and 15 with severe impairment who were in the chronic phase post-stroke underwent a diffusion-weighted imaging scan and motor function and impairment assessments. Different relationships existed between reconstruction methods, microstructural properties, and impairment and function. In severe stroke, fractional anisotropy (FA) emerged over and above apparent diffusion coefficient (ADC) and tract number to index CST integrity FA correlated with impairment and function, whereas ADC and tract number did not correlate. No significant differences between methods or microstructural properties were found in mild-moderate stroke. Our study demonstrates that CST reconstruction method influences the extraction of microstructural integrity in in iduals with chronic severe stroke, with FA appearing to be the most representative method. A similar line of investigation is warranted earlier post-stroke. Differences in this data set highlight the need to establish a common methodology for CST reconstruction and analysis which may eliminate discrepancies in interpreting DWI and enhance biomarker use post-stroke for motor function.
Publisher: Hindawi Limited
Date: 04-02-2019
DOI: 10.1155/2019/7092496
Abstract: Continuous theta burst stimulation (cTBS) is a form of noninvasive repetitive brain stimulation that, when delivered over the contralesional hemisphere, can influence the excitability of the ipsilesional hemisphere in in iduals with stroke. cTBS applied prior to skilled motor practice interventions may augment motor learning however, there is a high degree of variability in in idual response to this intervention. The main objective of the present study was to assess white matter biomarkers of response to cTBS paired with skilled motor practice in in iduals with chronic stroke. We tested the effects of stimulation of the contralesional hemisphere at the site of the primary motor cortex (M1c) or primary somatosensory cortex (S1c) and a third group who received sham stimulation. Within each stimulation group, in iduals were categorized into responders or nonresponders based on their capacity for motor skill change. Baseline diffusion tensor imaging (DTI) indexed the underlying white matter microstructure of a previously known motor learning network, named the constrained motor connectome (CMC), as well as the corticospinal tract (CST) of lesioned and nonlesioned hemispheres. Across practice, there were no differential group effects. However, when categorized as responders vs. nonresponders using change in motor behaviour, we demonstrated a significant difference in CMC microstructural properties (as measured by fractional anisotropy (FA)) for in iduals in M1c and S1c groups. There were no significant differences between responders and nonresponders in clinical baseline measures or microstructural properties (FA) in the CST. The present study identifies a white matter biomarker, which extends beyond the CST, advancing our understanding of the importance of white matter networks for motor after stroke.
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 26-07-2022
DOI: 10.1212/WNL.0000000000200517
Abstract: It is difficult to predict poststroke outcome for in iduals with severe motor impairment because both clinical tests and corticospinal tract (CST) microstructure may not reliably indicate severe motor impairment. Here, we test whether imaging biomarkers beyond the CST relate to severe upper limb (UL) impairment poststroke by evaluating white matter microstructure in the corpus callosum (CC). In an international, multisite hypothesis-generating observational study, we determined if (1) CST asymmetry index (CST-AI) can differentiate between in iduals with mild-moderate and severe UL impairment and (2) CC biomarkers relate to UL impairment within in iduals with severe impairment poststroke. We hypothesized that CST-AI would differentiate between mild-moderate and severe impairment, but CC microstructure would relate to motor outcome for in iduals with severe UL impairment. Seven cohorts with in idual diffusion imaging and motor impairment (Fugl-Meyer Upper Limb) data were pooled. Hand-drawn regions-of-interest were used to seed probabilistic tractography for CST (ipsilesional/contralesional) and CC (prefrontal remotor/motor/sensory osterior) tracts. Our main imaging measure was mean fractional anisotropy. Linear mixed-effects regression explored relationships between candidate biomarkers and motor impairment, controlling for observations nested within cohorts, as well as age, sex, time poststroke, and lesion volume. Data from 110 in iduals (30 with mild-moderate and 80 with severe motor impairment) were included. In the full s le, greater CST-AI (i.e., lower fractional anisotropy in the ipsilesional hemisphere, p 0.001) and larger lesion volume ( p = 0.139) were negatively related to impairment. In the severe subgroup, CST-AI was not reliably associated with impairment across models. Instead, lesion volume and CC microstructure explained impairment in the severe group beyond CST-AI ( p 's 0.010). Within a large cohort of in iduals with severe UL impairment, CC microstructure related to motor outcome poststroke. Our findings demonstrate that CST microstructure does relate to UL outcome across the full range of motor impairment but was not reliably associated within the severe subgroup. Therefore, CC microstructure may provide a promising biomarker for severe UL outcome poststroke, which may advance our ability to predict recovery in in iduals with severe motor impairment after stroke.
No related grants have been discovered for Jason Neva.