White Matter Integrity and Chronic Poststroke Upper Limb Function: An ENIGMA Stroke Recovery Analysis.

Area of Science:

• Neuroscience
• Neurology
• Rehabilitation Medicine

Background:

• The corticospinal tract (CST) is a key biomarker for upper limb motor function after stroke.
• Structural damage to the CST may necessitate compensatory roles of other white matter tracts for functional recovery.

Purpose of the Study:

• To investigate the relevance of alternative white matter tracts for upper limb motor function in chronic stroke survivors with varying degrees of CST damage.
• To determine if residual pathways compensate for CST integrity in stroke recovery.

Main Methods:

• Utilized the ENIGMA Stroke Recovery dataset (n=166) of chronic stroke patients with upper limb impairment.
• Quantified white matter integrity using fractional anisotropy (FA) for CST, superior longitudinal fascicle, and callosal fibers.
• Correlated FA values with upper limb motor function using the Fugl-Meyer upper extremity scale.

Main Results:

• In individuals with severe CST damage, higher FA in callosal fibers (r=0.49, P=0.025) and the superior longitudinal fascicle (r=0.51, P=0.018) correlated with better motor function.
• No significant associations were found in individuals with less severe CST damage.

Conclusions:

• Stroke survivors with significant CST damage rely on intact alternative pathways for motor function recovery.
• Residual white matter tracts play a compensatory role in achieving better upper limb outcomes after severe CST injury.