Magnetic resonance microimaging of the spinal cord in the SOD1 mouse model of amyotrophic lateral sclerosis detects motor nerve root degeneration

• Published in: NeuroImage (Orlando, Fla.) Vol. 58; no. 1; pp. 69 - 74
• Main Authors: Cowin, Gary J., Butler, Tim J., Kurniawan, Nyoman D., Watson, Charles, Wallace, Robyn H.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01-09-2011; Elsevier Limited
• Subjects: Amyotrophic lateral sclerosis; Amyotrophic Lateral Sclerosis - genetics; Amyotrophic Lateral Sclerosis - pathology; Animals; Cell Count; Contrast agents; Humans; Image Processing, Computer-Assisted; Magnetic Resonance Imaging; Mice; Mice, Inbred C57BL; Mice, Transgenic; Motor Neurons - pathology; Multiple sclerosis; Nerve Degeneration - pathology; Rodents; SOD1; Spinal cord; Spinal Cord - pathology; Spinal cord magnetic resonance microimaging; Spinal Nerve Roots - pathology; Superoxide Dismutase - genetics; Superoxide Dismutase-1; Amyotrophic lateral sclerosis; Spinal cord magnetic resonance microimaging; SOD1
• ISSN: 1053-8119; 1095-9572
• DOI: 10.1016/j.neuroimage.2011.06.003

Amyotrophic lateral sclerosis (ALS) is characterized by selective degeneration of motor neurons. Current imaging studies have concentrated on areas of the brain and spinal cord that contain mixed populations of sensory and motor neurons. In this study,
ex vivo magnetic resonance microimaging (MRM) was used to separate motor and sensory components by visualizing individual dorsal and ventral roots in fixed spinal cords. MRM at 15
μm in plane resolution enabled the axons of pure populations of sensory and motor neurons to be measured in the lumbar region of the SOD1 mouse model of ALS. MRM signal intensity increased by 38.3% (
p
<
0.05) exclusively in the ventral motor nerve roots of the lumbar spinal cord of ALS-affected SOD1 mice compared to wildtype littermates. The hyperintensity was therefore limited to white matter tracts arising from the motor neurons, whereas sensory white matter fibers were unchanged. Significant decreases in ventral nerve root volume were also detected in the SOD1 mice, which correlated with the axonal degeneration observed by microscopy. These results demonstrate the usefulness of MRM in visualizing the ultrastructure of the mouse spinal cord. The detailed 3D anatomy allowed the processes of pure populations of sensory and motor neurons to be compared.
► Magnetic resonance microimaging can detect axonal spinal cord damage in SOD1 mice. ► MRM signal intensity is increased in ventral nerves of SOD1 mice. ► Increasing MRM signal intensity correlates with decreasing axon number. ► MRM motor nerve root volume is decreased in SOD1 mice. ► High resolution MRM at 10
μm provided close to optical microscopy resolution.