Diffusional Kurtosis Imaging and Motor Outcome in Acute Ischemic Stroke

Area of Science:

• Neuroimaging
• Stroke Neurology
• Diffusion MRI

Background:

• Motor impairment is a common and significant deficit following stroke.
• Early detection of microstructural changes in the corticospinal tract is crucial for understanding stroke recovery.
• Conventional diffusion metrics may not fully capture the complexity of early post-stroke neural changes.

Purpose of the Study:

• To evaluate the ability of diffusional kurtosis imaging (DKI) to detect acute microstructural changes in the corticospinal tract (CST) after ischemic stroke.
• To assess the correlation between DKI-derived CST metrics and motor impairment severity at 3 months post-stroke.

Main Methods:

• Seventeen patients with first-ever ischemic stroke underwent brain MRI including DKI within 4 days of symptom onset.
• Corticospinal tract (CST) microstructural changes were assessed using DKI metrics (mean diffusivity, mean kurtosis, axial kurtosis, axonal water fraction) in lesioned and contralateral hemispheres.
• Motor function was evaluated using the Fugl-Meyer Upper Extremity Motor scale in the acute phase and at 3 months post-stroke.

Main Results:

• Axial kurtosis showed the largest signal change (12% increase) in the lesioned CST compared to the contralateral side.
• Strongest correlations with 3-month motor function (Fugl-Meyer score) were observed for the lesioned/contralateral CST mean kurtosis (ρ = -0.85) and axial kurtosis (ρ = -0.78) ratios.
• DKI metrics, particularly kurtosis-related ones, demonstrated greater sensitivity to early CST microstructural alterations.

Conclusions:

• Diffusional kurtosis imaging is sensitive to early microstructural changes in the corticospinal tract following ischemic stroke.
• Kurtosis-based diffusion metrics show significant potential for predicting motor impairment at 3 months post-stroke.
• DKI may offer a valuable tool for early assessment and prognosis in stroke patients.