Diffusion tensor imaging in multiple sclerosis at different final outcomes.

Area of Science:

• Neuroimaging
• Neurology
• Biomedical Engineering

Background:

• Multiple Sclerosis (MS) presents diverse long-term outcomes, necessitating methods to differentiate demyelination from axonal degeneration.
• Evaluating the relative contributions of these pathological processes is crucial for understanding MS progression.

Purpose of the Study:

• To employ diffusion tensor imaging (DTI) to assess demyelination and axonal degeneration in the corpus callosum (CC) of MS patients.
• To correlate DTI metrics with different long-term MS disease courses.

Main Methods:

• DTI measures, including mean diffusivity (MD), fractional anisotropy (FA), axial diffusivity (AD), and radial diffusivity (RD), were analyzed in the CC of 31 MS patients.
• Patients were categorized by disease course: secondary progressive (n=13), non-progressive (n=11), and monophasic (n=7).
• A cohort of 254 attack-onset MS patients with 50-year follow-up and five healthy controls were included.

Main Results:

• Secondary progressive MS patients showed increased RD and reduced FA in the CC compared to other groups.
• No significant differences in DTI parameters were found between non-progressive, monophasic MS groups, and controls.
• Axial diffusivity (AD) did not differ across the groups, suggesting it's not a key indicator of long-term outcome.

Conclusions:

• Elevated RD in the corpus callosum is indicative of significant myelin loss, characterizing secondary progressive MS.
• Normal RD values in clinically isolated syndrome and non-progressive MS groups confirm their generally benign nature.
• Demyelination, identified by increased RD, serves as a distinguishing feature for secondary progressive MS, differentiating it from less aggressive forms.