Measuring myelin repair and axonal loss with diffusion tensor imaging.

Area of Science:

• Neuroimaging
• Neurology
• Biomedical Engineering

Background:

• Multiple Sclerosis (MS) is a chronic neurological disease affecting brain tissue integrity.
• Diffusion Tensor Imaging (DTI) offers a sensitive method to assess microstructural changes in the brain.
• DTI is valuable for monitoring disease progression and treatment efficacy in clinical trials.

Purpose of the Study:

• To utilize DTI to longitudinally evaluate changes in brain tissue integrity.
• To assess DTI metrics in patients with MS undergoing treatment with natalizumab.
• To correlate DTI findings with lesion activity and long-term tissue changes.

Main Methods:

• Serial DTI scans were performed on 21 MS patients over 12 months.
• Regions of interest in normal-appearing white and gray matter, and gadolinium-enhancing lesions were analyzed.
• Fractional Anisotropy (FA), λ(∥), λ(⊥), and Mean Diffusivity (MD) were quantified.
• Mixed-model regression analysis assessed DTI changes per month.

Main Results:

• Fractional Anisotropy (FA) increased in active lesions but decreased in normal-appearing brain tissue (NABT).
• Changes in FA were attributed to alterations in λ(⊥) within lesions and λ(∥) within NABT.
• Elevated baseline λ(⊥) in active lesions predicted future T1 black hole formation.
• Mean Diffusivity (MD) remained stable in both lesion types and NABT.

Conclusions:

• DTI measures demonstrated significant longitudinal changes in both active MS lesions and normal-appearing brain tissue.
• Observed DTI changes suggest potential remyelination in acute lesions and chronic axonal damage in normal-appearing white matter.
• DTI is a promising imaging biomarker for assessing neuroprotection in MS treatment studies.