Axial MRI biomarkers of spinal cord damage to predict future walking and motor function: a retrospective study

Andrew C. Smith,David Dungan,Christina Draganich,Jeffrey C. Berliner,Stephanie R. Albin,Mitch Sevigny,James M. Elliott,Kenneth A. Weber II,Denise R. O’Dell

doi:10.1038/s41393-020-00561-w

Abstract

Study designRetrospective.ObjectivesPrimary: to assess if axial damage ratios are predictors of future walking after spinal cord injury (SCI), and if they add any predictive value if initial neurological impairment grades are available. Secondary: to determine if lateral spinal cord regions are predictors of future lower extremity motor scores (LEMS).SettingUniversity/hospital.MethodsAxial T2-weighted MRIs were used. Axial damage ratios and non-damaged lateral cord volumes were calculated. Each participant answered at 1 year after SCI, “Are you able to walk for 150 feet? (45.72 meters)” For the secondary aim, right and left LEMS were used.ResultsIn total, 145 participants were selected. Individuals that could walk had smaller ratios than those that were unable. Walking and axial damage ratios were negatively correlated. A 0.374 ratio cut-off showed optimal sensitivity/specificity. When initial neurological grades were used, axial damage ratios did not add predictive value. Forty-two participants had LEMS available and were included for the secondary aim. Right cord regions and right LEMS were positively correlated and left regions and left LEMS, but these variables were also correlated with each other.ConclusionsAxial damage ratios were significant predictors of walking ability 1 year after SCI. However, this measure did not add predictive value over initial neurological grades. Lateral cord regions correlated with same-side LEMS, but the opposite was also found, calling this biomarker’s specificity into question. Axial damage ratios may be useful in predicting walking after SCI if initial neurological grades are unavailable.SponsorshipThis research was funded by a National Institutes of Health award, National Institute of Child Health and Development—NIH R03HD094577.

Highlights

After a spinal cord injury (SCI), the recovery of walking ability is among the top priorities for individuals with SCI [1]
The secondary aim of this study was to determine if spared tissue in the lateral cord regions may be significant predictors of future lower extremity motor scores (LEMS)
Individuals that were able to walk 150 feet (45.72 meters) 1 year after SCI had a smaller axial damage ratio than those that were unable to walk

Summary

Introduction

After a spinal cord injury (SCI), the recovery of walking ability is among the top priorities for individuals with SCI [1]. An important factor driving these clinical prediction rules is the extent of residual sensorimotor function, which is used to classify patients into American Spinal Injury Association Impairment Scales (AIS) [5] Those with motor incomplete injuries who have extensive voluntary residual motor function in their lower extremities receive a favorable prognosis for walking recovery [2,3,4]. After SCI, sensorimotor testing for proper AIS classification may not be possible to perform—in instances of sedation, polytrauma, and/or concomitant brain injury—the clinical prediction rules would not be available or applicable In these instances, magnetic resonance imaging (MRI) biomarkers may be especially useful to aide in the prediction of future walking ability [7, 8]

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