To assess the association between automatically measured medulla oblongata volume (MOV) and spinal cord cross-sectional area (SC-CSA) as well as their associations with clinical disability in multiple sclerosis (MS).

Spinal cord atrophy is well known to be associated with clinical disability in MS. Manually-measured MOV on brain MRI has previously been proposed as a potential proxy for spinal cord atrophy.

161 MS patients were scanned on 1.5T MRI brain and cervical spinal cord sequences were collected. 126  patients had relapsing-remitting MS (RRMS) and 35 had secondary progressive MS (SPMS) disease course. Clinical disability was quantified via the Expanded Disability Status Scale (EDSS). MOV and SC-CSA (measured between C2-C3) were automatically calculated using FreeSurfer and Spinal Cord Toolbox, respectively. RRMS and SPMS patients were compared with respect to both MRI-derived measures. Correlations between MOV and SC-CSA and their associations with EDSS were also assessed. 

Compared to RRMS patients, SPMS patients presented with smaller MO volume (p=.003) and smaller C2-C3 CSA (p<.0001). When considering the entire cohort, MOV and SC-CSA were correlated (r=.574, p<.0001). A similar correlation was found in RRMS patients (r=.570, p<.0001) but somewhat weaker in SPMS patients (r=.355, p=.037). For the whole sample, correlations were found between MOV (r_s= -.446,p<.0001) and SC-CSA (r_s = -.572, p<.0001) with EDSS. For RRMS patients, the associations were similar in degree (r_s = -.329, p=.001 and r_s=-.332, p=.002, respectively) whereas for SPMS patients, the strength of the correlations diverged (r_s = -.364,p=.029 and r_s= -.779, p<.0001, respectively).

Our findings demonstrate that MOV correlates well with SC-CSA and can be reliably segmented in an automatic fashion. Moreover, MOV may potentially serve as a surrogate measure for SC atrophy in RRMS when cervical spine MRI is not available.