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Evolution of cortical activation during recovery from corticospinal tract infarction
R S Marshall1, G M Perera, R M Lazar
1Columbia-Presbyterian Medical Center, Columbia University, New York, NY, USA. rsm2@columbia.edu
Background And Purpose:
Recovery from hemiparesis due to corticospinal tract infarction is well documented, but the mechanism of recovery is unknown. Functional MRI (fMRI) provides a means of identifying focal brain activity related to movement of a paretic hand. Although prior studies have suggested that supplementary motor regions in the ipsilesional and contralesional hemisphere play a role in recovery, little is known about the time course of cortical activation in these regions as recovery proceeds.
Methods:
Eight patients with first-ever corticospinal tract lacunes causing hemiparesis had serial fMRIs within the first few days after stroke and at 3 to 6 months. Six healthy subjects were used as controls. Statistically significant voxels during a finger-thumb opposition task were identified with an automated image processing program. An index of ipsilateral versus contralateral activity was used to compare relative contributions of the 2 hemispheres to motor function in the acute and chronic phases after stroke.
Results:
Controls showed expected activation in the contralateral sensorimotor cortex (SMC), premotor, and supplementary motor areas. Stroke patients differed from control patients in showing greater activation in the ipsilateral SMC, ipsilateral posterior parietal, and bilateral prefrontal regions. Compared with the nonparetic hand, the ratio of contralateral to ipsilateral SMC activity during movement of the paretic hand increased significantly over time as the paretic hand regained function.
Conclusions:
The evolution of activation in the SMC from early contralesional activity to late ipsilesional activity suggests that a dynamic bihemispheric reorganization of motor networks occurs during recovery from hemiparesis.
Insights
Brain reorganization aids recovery from hemiparesis after stroke. Functional MRI (fMRI) shows motor network shifts from contralesional to ipsilesional activity as function returns.
Area of Science:
- Neuroscience
- Neurology
- Radiology
Background:
- Recovery from hemiparesis following corticospinal tract infarction is recognized, but the underlying mechanisms remain unclear.
- Functional MRI (fMRI) is a key tool for visualizing brain activity during hand movement.
- Previous research indicated supplementary motor regions' involvement, but the temporal dynamics of cortical activation during recovery are not well understood.
Purpose of the Study:
- To investigate the time course of cortical activation patterns during recovery from hemiparesis.
- To explore the role of bihemispheric motor network reorganization in functional recovery after stroke.
Main Methods:
- Serial fMRI scans were conducted on eight hemiparetic stroke patients and six healthy controls.
- Patients underwent imaging within days of stroke onset and again at 3–6 months.
- A finger-thumb opposition task was used to assess motor function and associated brain activity, comparing ipsilateral and contralateral sensorimotor cortex (SMC) contributions.
Main Results:
- Healthy controls exhibited typical contralateral SMC activation.
- Stroke patients showed increased ipsilateral SMC, parietal, and prefrontal activation compared to controls.
- The ratio of contralesional to ipsilesional SMC activity increased significantly over time in stroke patients as motor function improved.
Conclusions:
- Motor network recovery involves a dynamic bihemispheric reorganization.
- The shift from early contralesional to later ipsilesional SMC activation is a hallmark of functional recovery.
- These findings provide insights into the neural plasticity underlying motor recovery after stroke.