Spinal Cord Injury Severity Influences Microstructural Alterations in the Supraspinal Somatosensory Pathways.

RATIONALE AND OBJECTIVES: Spinal cord injury (SCI) induces structural remodeling of supraspinal somatosensory pathways; however, the specific microstructural alterations across different injury severities remain unclear. This study aimed to investigate these changes to inform severity-specific therapies for sensory recovery. MATERIALS AND METHODS: We included 20 patients with complete SCI (CSCI), 16 with incomplete SCI (ISCI), and 32 sex- and age-matched healthy controls. Using diffusion tensor imaging (DTI) and deterministic fiber tractography, fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD), and radial diffusivity (RD) were quantitatively analyzed in the medial lemniscus (ML), spinothalamic tract (STT), and thalamocortical projections from the thalamus to six cortical subregions. Group comparisons and correlation analyses with sensory scores were performed. RESULTS: Severity-dependent patterns of microstructural alterations were observed. The ISCI group exhibited concurrent increases in AD and MD within the ML and STT. In thalamocortical projections, widespread elevations in RD and MD were found in sensory, motor, frontal, and parietal pathways in ISCI. In contrast, CSCI showed more restricted increases in RD and MD, mainly confined to sensory and parietal projections. No significant group differences in FA were detected. Notably, in CSCI patients, sensory scores were negatively correlated with MD and RD values in the thalamo-sensory cortical pathway. CONCLUSION: This study demonstrated that SCI induces severity-dependent remodeling within supraspinal somatosensory pathways, providing a foundation for targeted and stratified clinical therapeutic strategies. ISCI is characterized by the coexistence of widespread axonal injury and repair, while CSCI features localized demyelination correlated with sensory dysfunction.