Long-term impact of spinal cord reserve on disability accumulation in multiple sclerosis

Background: This study aimed to test the association between cervical canal area (CCaA), a proxy for spinal cord reserve, measured at the first demyelinating event and disability accumulation in people with multiple sclerosis (pwMS). Methods: Subjects with a clinically isolated syndrome (CIS) enrolled at Cemcat between January 2009 and December 2014 were included if they had a baseline brain three-dimensional T1-weighted image (3DT1WI), at least a 10-year clinical follow-up, and diagnosis of MS during follow-up. Clinical data were collected at the onset of CIS, and at 6 months, 1 year, 5 years, 10 years, and at the last follow-up visit. CCaA was measured on 3DT1WI using a validated segmentation pipeline at the C2/C3 and C3/C4 disc levels. Results: Of the initial 121 pwMS, the final cohort comprised 81 pwMS with CCaA measures at C2/C3 and 76 pwMS at C3/C4. Linear mixed-effects models showed that while CCaA was not predictive of Expanded Disability Status Scale (EDSS) at disease onset, its influence on disability accumulation increased over time (C3/C4: CCaA-Time interaction, β = −0.023, p = 0.034). Conclusion: Larger spinal cord reserve at disease onset appeared to be associated with a slower rate of disability accumulation, supporting the concept of spinal cord reserve.