Quantification of normal-appearing white matter tract integrity in multiple sclerosis: a diffusion kurtosis imaging...

Area of Science:

• Neuroimaging
• Neurology
• Biomedical Engineering

Background:

• Multiple sclerosis (MS) is a demyelinating disease affecting the central nervous system.
• Normal-appearing white matter (NAWM) in MS patients exhibits subtle pathological changes.
• Standard diffusion tensor imaging (DTI) has limitations in characterizing these microstructural alterations.

Purpose of the Study:

• To characterize pathological changes in MS NAWM using novel diffusion kurtosis imaging (DKI)-derived white matter tract integrity (WMTI) metrics.
• To investigate the association between WMTI metrics and clinical parameters in MS patients.

Main Methods:

• MRI scans were acquired from 32 relapsing-remitting MS patients and 19 healthy controls.
• DKI-derived WMTI metrics (intra-axonal diffusivity, axonal water fraction, tortuosity, extra-axonal diffusivity) were calculated.
• Tract-based spatial statistics and region of interest analyses were performed to compare groups and assess correlations with clinical scores.

Main Results:

• MS patients showed significantly increased mean diffusivity and radial extra-axonal diffusivity in NAWM compared to controls.
• Fractional anisotropy, axonal water fraction, intra-axonal diffusivity, and tortuosity were significantly decreased in MS patients.
• Axonal water fraction in the corpus callosum correlated with Expanded Disability Status Scale scores, and most WMTI metrics correlated with the Symbol Digits Modality Test.

Conclusions:

• WMTI metrics are sensitive to microstructural changes in the NAWM of MS patients.
• These novel metrics offer a more pathologically specific and clinically meaningful complement to standard DTI metrics.
• WMTI may enhance the assessment of disease severity and progression in multiple sclerosis.