Spinal cord lesion characteristics and early standing ability with and without epidural stimulation

Current evidence suggests that spinal cord epidural stimulation (scES) can promote aspects of motor recovery for standing, stepping and volitional lower limb movement in research participants with spinal cord injury (SCI), although the extent of such recovery varies among individuals. The goal of this retrospective cohort study was to assess (i) whether the early application of scES, prior to any training with scES, is sufficient to enhance standing ability; and (ii) which magnetic resonance imaging (MRI) biomarkers of spinal cord lesion, if any, are associated with early responsiveness to scES for standing. Twenty-nine non-ambulatory individuals with chronic, severe SCI (n = 27 clinically motor complete; n = 2 motor incomplete) underwent spinal cord MRI and were subsequently implanted with scES. Standing ability was assessed prior to epidural stimulator implant and after implant with scES parameters targeted to facilitate standing (Stand-scES). T2-weighted MRI was used to measure the following spinal cord lesion characteristics: lesion length, midsagittal tissue bridges, and estimates of spared tissue in the anterior, posterior, right, and left spinal cord regions. Early application of continuous Stand-scES significantly improved the ability to stand for longer periods (+ 17%, P = 0.040) and with greater outcomes of independent lower limb extension (P values 0.009-0.042) compared to pre-implant, although responses varied across participants. Notably, shorter spinal cord lesion length and the presence of tissue bridge at the lesion site were positively associated with standing ability promoted by Stand-scES (P values 0.011-0.033). The proposed MRI lesion markers may clarify expectations of early standing recovery with Stand-scES.