Cervical Atrophy Following Complete Thoracic Spinal Cord Injury: Insights From a Multinational Cohort.

BACKGROUND: Spinal cord injury (SCI) results in neurodegeneration both at and above the lesion site. While cervical cord atrophy is well characterised in populations of mixed cervical, thoracic and/or lumbar injuries, the remote morphological changes in cervical cord following thoracic SCI remain unclear. The present study aimed to quantify cervical spinal cord morphology at C2-C3 in individuals with complete thoracic SCI and compare these metrics to matched controls. METHODS: Participants were 52 adults with complete thoracic SCI and 55 neurologically healthy, able-bodied controls matched for age and sex. Extracted cervical metrics included mean cross-sectional area (CSA), antero-posterior (AP) and right-left (RL) diameters, eccentricity, solidity, orientation and cord length. Group differences were assessed using linear mixed models adjusted for age, sex and scanning sites. Impacts of experiencing SCI-related chronic neuropathic pain on these metrics were explored. RESULTS: Compared to controls, the thoracic SCI group showed significantly reduced cervical CSA and AP/RL diameters, consistent with remote atrophy, and increased eccentricity, indicating a more flattened cord profile. Solidity, orientation and cord length showed no group differences, supporting metric reliability and absence of segmentation artefacts. Although no difference was evident among the SCI groups, those experiencing chronic neuropathic pain had larger eccentricity than controls. CONCLUSIONS: Complete thoracic SCI is associated with significant remote cervical cord degeneration, even in the absence of direct cervical injury. Results highlight that neurodegenerative processes propagate along ascending and descending spinal pathways. Cervical morphometry metrics, particularly CSA and eccentricity, may represent biomarkers of distal neurodegeneration following thoracic SCI and inform future therapeutic strategies.