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|Title: ||Proportional recovery after stroke depends on corticomotor integrity|
|Authors: ||Byblow, Winston|
|Issue Date: ||17-Nov-2015|
|Publisher: ||to American Neurological Association|
|Citation: ||Byblow, W. D., C. M. Stinear, P. A. Barber, M. A. Petoe & S. J. Ackerley (2015). Proportional recovery after stroke depends on corticomotor integrity. Annals of neurology: [epub ahead of print].|
For most patients the resolution of upper limb impairment during the first six months after stroke is 70% of the maximum possible. We sought to identify candidate mechanisms of this proportional recovery. We hypothesized that the proportional resolution of upper limb impairment depends on ipsilesional corticomotor pathway function, is mirrored by the proportional recovery of excitability in this pathway, and is unaffected by upper limb therapy dose.
Upper limb impairment was measured in 93 patients at 2, 6, 12 and 26 weeks after first-ever ischaemic stroke. Motor evoked potentials and motor threshold were recorded from extensor carpi radialis using transcranial magnetic stimulation, and fractional anisotropy in the posterior limbs of the internal capsules was determined with diffusion-weighted MRI.
Initial impairment score, the presence of motor evoked potentials and fractional anisotropy asymmetry were the only predictors of impairment resolution, indicating a key role for corticomotor tract function. By 12 weeks, upper limb impairment resolved by 70% in patients with motor evoked potentials regardless of their initial impairment, and ipsilesional rest motor threshold also resolved by 70%. The resolution of impairment was insensitive to upper limb therapy dose.
These findings indicate that upper limb impairment resolves by 70% of the maximum possible regardless of initial impairment, but only for patients with intact corticomotor function. Impairment resolution seems to reflect spontaneous neurobiological processes that involve the ipsilesional corticomotor pathway. A better understanding of these mechanisms could lead to interventions that increase the resolution of impairment above 70%. This article is protected by copyright. All rights reserved.|
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