Radial diffusivity predicts demyelination in ex vivo multiple sclerosis spinal cords

Area of Science:

• Neuroimaging
• Pathology
• Multiple Sclerosis Research

Background:

• Multiple sclerosis (MS) involves demyelination, axonal degeneration, and inflammation.
• Previous animal studies suggested diffusion tensor imaging (DTI) could differentiate axonal and myelin pathologies.

Purpose of the Study:

• To correlate DTI findings with histochemical staining for demyelination and axonal damage.
• To investigate DTI's ability to differentiate pathologies in ex vivo human MS spinal cords.

Main Methods:

• DTI performed on 9 MS and 5 control fixed human cervical spinal cord blocks.
• Histochemical staining (LFB, Bielschowsky silver, H&E) for myelin and axonal integrity.
• Semi-quantitative grading of demyelination and manual axonal counts.
• Correlation of DTI parameters (ADC, RA, axial/radial diffusivity) with histopathology.

Main Results:

• Increased radial diffusivity correlated with demyelination severity.
• Decreased relative anisotropy (RA) observed in moderate-severe demyelination.
• Radial diffusivity, ADC, and RA altered with increasing axonal loss.
• Axial diffusivity did not significantly correlate with axonal density.

Conclusions:

• Radial diffusivity may indicate demyelination but is not specific to it in chronic MS.
• Radial diffusivity alterations also reflect axonal injury.
• DTI parameters, particularly radial diffusivity, can serve as markers of tissue integrity in MS lesions.
• Findings support ongoing in vivo DTI studies for MS.