Relationships between functional and structural corticospinal tract integrity and walking post stroke

Area of Science:

• Neuroscience
• Rehabilitation Medicine
• Biomedical Engineering

Background:

• Stroke recovery heavily relies on corticospinal tract (CST) integrity for upper limb function.
• The relationship between CST integrity and lower limb function post-stroke is less understood.
• Assessing lower limb motor control is crucial for patient mobility and quality of life.

Purpose of the Study:

• To investigate the association between walking impairment and the structural/functional integrity of the CST in chronic stroke patients.
• To determine if lower limb functional connectivity and CST structural integrity predict walking ability.

Main Methods:

• Utilized transcranial magnetic stimulation (TMS) and electromyography (EMG) to measure lower limb motor evoked potentials.
• Calculated the functional connectivity ratio (FCR) from ipsilateral and contralateral motor cortex outputs to the vastus lateralis.
• Assessed CST structural integrity using diffusion tensor MRI (DT-MRI) to measure fractional anisotropy (FA) asymmetry.

Main Results:

• The FCR of the paretic leg showed a correlation with walking impairment; increased ipsilateral connectivity was linked to slower walking speeds.
• Asymmetrical FA values, indicating reduced structural integrity of the lesioned CST, correlated with greater walking impairment.
• A strong positive correlation was observed between FCR and FA asymmetry.

Conclusions:

• Greater ipsilesional CST structural damage and increased functional connectivity from the contralesional motor cortex to the paretic lower limb are associated with more severe walking impairment.
• Structural and functional CST damage measures can inform the selection of tailored therapeutic strategies for stroke survivors.