Myotome Conversion from Zero Reveals Recovery Beyond Pooled Motor Scores After Cervical Spinal Cord Injury: A Proof-of-Concept Analysis

Study Design: Retrospective proof-of-concept analysis Objective: We propose myotome conversion from zero (MC-0) as a proof-of-concept analytic metric that can better differentiate segmental recovery patterns obscured by pooled motor scores and AIS grade. Setting: Data from the Spinal Cord Injury Model Systems Database (SCIMS; 2016–2023). Methods: Retrospective proof-of-concept analysis of participants with traumatic cervical SCI from the SCIMS Database. For each key upper-extremity myotome we tabulated the number of low MC-0 (improvement to 1-2/5 from a baseline motor score of 0/5), and high MC-0 (improvement to > 3/5 from a baseline of 0/5). We analyzed the proportion of upper-extremity myotomes demonstrating MC-0, the proportion without conversion, the distribution of conversion by neurological level of injury, and clinically meaningful UEMS changes, alongside AIS grade stability, between inpatient rehabilitation admission and discharge. Results: 1,275 participants from 16 SCIMS sites were analyzed. Across 10 key myotomes (C5–T1, bilaterally), nearly half of initially paralyzed upper-extremity myotomes showed some recovery between rehabilitation admission and discharge (31.8% low, 14.3% high conversion), while 53.9% showed no conversion. MC-0 was operationalized using registry data and explained an additional 23–30% of variation in discharge UEMS beyond admission UEMS across C4–C6 injuries. Notably, many participants demonstrated myotome conversions across multiple key myotomes without a change in AIS grade. Conclusion: MC-0 assessment is feasible in registry data and provides a more granular view of early motor recovery after cervical SCI. MC-0 may complement or replace traditional outcomes in natural history studies and early neurorecovery trials. Sponsorship: This work was supported by Kringle Pharma, Inc and by the National Institute on Disability, Independent Living, and Rehabilitation Research (NIDILRR), U.S. Department of Health and Human Services, through the 90IFST0026, NIDILRR grant number 90SIMS009-01 . The contents do not necessarily represent the policy of the Department of Health and Human Services.