Post-mortem evaluation of intervertebral disc degeneration using magnetic resonance imaging and magnetisation transfer ratio in chondrodystrophic and non-chondrodystrophic dogs: a pilot study

Intervertebral disc degeneration is a frequent and early condition in chondrodystrophic dogs, which can lead to neurological disorders due to compression of the spinal cord. The symptoms include pain, reduced mobility and even paralysis. Magnetic resonance imaging (MRI) is currently the reference technique for analysing this pathology. Based on T2-weighted MRI sequences, Pfirrmann's classification provides a qualitative assessment of the evolution of disc lesions. However, this approach remains subjective and subject to inter-observer variability, underscoring the need for more objective and reproducible tools. The aim of this pilot study was to explore the value of the magnetization transfer ratio (MTR) as a quantitative tool for a more accurate assessment of disc degeneration. MRI acquisitions were performed on spinal columns harvested post-mortem from 9 chondrodystrophic and non-chondrodystrophic dogs of various breeds. 181 intervertebral discs were graded according to the Pfirrmann scale, and MTR values were measured within the nucleus pulposus, annulus fibrosus and the entire disc. Moreover a correlation between imaging findings, macroscopic evaluation with Thompson grade and histological staining was made to ensure accurate assessment of intervertebral disc degeneration. Statistical analysis was carried out to examine the correlation between these values and the degree of disc degeneration. The results show a positive correlation between increased MTR and the severity of Pfirrmann grades. These data suggest that MTR MRI could provide a complementary tool for more reliable and standardised quantification of disc degeneration, reducing subjective bias. This approach could improve diagnostic accuracy and early assessment of disc alterations, with important implications for therapeutic management. Nonetheless, an in vivo validation of this approach remains necessary.