Journal Article

Motor system activation after subcortical stroke depends on corticospinal system integrity

Nick S. Ward, Jennifer M. Newton, Orlando B. C. Swayne, Lucy Lee, Alan J. Thompson, Richard J. Greenwood, John C. Rothwell and Richard S. J. Frackowiak

in Brain

Published on behalf of The Guarantors of Brain

Volume 129, issue 3, pages 809-819
Published in print March 2006 | ISSN: 0006-8950
Published online January 2006 | e-ISSN: 1460-2156 | DOI: https://dx.doi.org/10.1093/brain/awl002
Motor system activation after subcortical stroke depends on corticospinal system integrity

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Movement-related brain activation patterns after subcortical stroke are characterized by relative overactivations in cortical motor areas compared with controls. In patients able to perform a motor task, overactivations are greater in those with more motor impairment. We hypothesized that recruitment of motor regions would shift from primary to secondary motor networks in response to impaired functional integrity of the corticospinal system (CSS). We measured the magnitude of brain activation using functional MRI during a motor task in eight chronic subcortical stroke patients. CSS functional integrity was assessed using transcranial magnetic stimulation to obtain stimulus/response curves for the affected first dorsal interosseus muscle, with a shallower gradient representing increasing disruption of CSS functional integrity. A negative correlation between the gradient of stimulus/response curve and magnitude of task-related brain activation was found in several motor-related regions, including ipsilesional posterior primary motor cortex [Brodmann area (BA) 4p], contralesional anterior primary motor cortex (BA 4a), bilateral premotor cortex, supplementary motor area, intraparietal sulcus, dorsolateral prefrontal cortex and contralesional superior cingulate sulcus. There were no significant positive correlations in any brain region. These results suggest that impaired functional integrity of the CSS is associated with recruitment of secondary motor networks in both hemispheres in an attempt to generate motor output to spinal cord motoneurons. Secondary motor regions are less efficient at generating motor output so this reorganization can only be considered partially successful in reducing motor impairment after stroke.

Keywords: functional brain imaging; motor recovery; motor system; stroke; BA = Brodmann area; CSS = corticospinal system; FDI = first dorsal interosseus; fMRI = functional MRI; MEP = motor evoked potential; NHPT = nine hole peg test; rMT = resting motor threshold; SMA = supplementary motor area; SPM = Statistical Parametric Mapping; TMS = transcranial magnetic stimulation; VAS = visual analogue scale

Journal Article.  7441 words.  Illustrated.

Subjects: Neurology ; Neuroscience

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