Clinical Subsets of Central Cord Syndrome: Is it a Distinct Entity from Other Forms of Incomplete Tetraplegia for Research?

Central cord syndrome (CCS) is the most prevalent and debated incomplete spinal cord injury (SCI) syndrome, with its hallmark feature being more pronounced weakness of the upper extremities compared to the lower extremities. Varying definitions encapsulate multiple clinical features under the single umbrella term of CCS, complicating evaluation of its frequency, prognosis discussions, and outcomes research. Oftentimes, people with CCS are excluded from research protocols, as it is thought to have a favorable prognosis, but the vague nature of CCS raises doubts about the validity of this practice. The objective of this study was to categorize CCS into specific subsets with clear quantifiable differences, to assess whether this would enhance the ability to determine if individuals with CCS or its subsets exhibit distinct neurological and functional outcomes relative to others with incomplete tetraplegia. This study retrospectively reviewed individuals with new motor incomplete tetraplegia from traumatic SCI who enrolled in the Spinal Cord Injury Model Systems (SCIMS) database from 2010 to 2020. Through an assessment of the prevailing criteria for CCS, coupled with data analysis, we used two key criteria, including the severity of distal upper extremity weakness (i.e., hands and fingers) and extent of symmetry, to delineate three CCS subsets: Full CCS, Unilateral CCS, and Borderline CCS. Of the 1,490 participants in our sample, 17.5% had Full, 25.6% Unilateral, and 9% Borderline CCS, together encompassing more than 50% of motor incomplete tetraplegia cases. Despite the increased sensitivity and specificity of these subsets compared to existing quantifiable criteria, substantial variability in clinical presentation was still observed. Overall, individuals meeting CCS subset criteria showed a higher likelihood of AIS D grade compared to those with motor incomplete tetraplegia without CCS, from admission to the 1-year follow-up. The upper extremity motor score (UEMS) for those with CCS was lower on admission, a difference that diminished by discharge, while their lower extremity motor score (LEMS) consistently remained higher compared to those without CCS. However, these neurological distinctions did not result in significant functional differences, as lower and upper extremity functional outcomes at discharge were mostly similar to those with motor incomplete tetraplegia, with some significant differences observed within those with AIS D grade. The AIS grade seems to remain the foremost determinant influencing neurological and functional outcomes, rather than the diagnosis of CCS. We recommend that future studies consider incorporating motor incomplete tetraplegia into their inclusion/exclusion criteria, instead of relying on criteria specific to CCS. While there remains clinical value in characterizing an injury pattern as CCS and perhaps using the different subsets to better characterize the impairments, it does not appear to be a useful research criterion.