Collateral nerve fibers in human spinal cord: visualization with magnetic resonance diffusion tensor imaging

Area of Science:

• Neuroimaging
• Biophysics
• Anatomy

Background:

• Diffusion tensor magnetic resonance imaging (DT-MRI) offers structural insights into nerve fiber tissues.
• The primary eigenvector of the diffusion tensor aligns with nerve fibers, particularly longitudinally in the spinal cord.

Purpose of the Study:

• To investigate if orthogonal collateral nerve fibers in the spinal cord create an organized arrangement of second eigenvectors.
• To validate DT-MRI's capability in visualizing detailed spinal cord fiber architecture.

Main Methods:

• Performed line scan diffusion imaging on a clinical MR scanner for DT-MRI scans.
• Acquired axial sections of a human cervical spinal cord specimen and four normal volunteers at varying resolutions.
• Used light microscopy on a fixed and stained spinal cord specimen for detailed collateral fiber architecture analysis.

Main Results:

• Diffusion was anisotropic in both white and gray matter of the spinal cord specimen, with distinct fractional anisotropy (FA) values.
• Volunteer FA values were comparable to the specimen, indicating consistent measurements.
• Second eigenvector directions in DT-MRI showed a clear pattern correlating with collateral nerve fibers observed in histology.

Conclusions:

• DT-MRI can non-invasively reveal the complex fiber architecture of the human spinal cord.
• The arrangement of second eigenvectors accurately reflects the distribution of collateral nerve fibers.
• This study confirms the utility of DT-MRI for detailed neuroanatomical investigation of the spinal cord.