Spinal cord imaging markers and recovery of standing with epidural stimulation in individuals with clinically motor complete spinal cord injury

Spinal cord epidural stimulation (scES) is an intervention to restore motor function in those with severe spinal cord injury (SCI). Spinal cord lesion characteristics assessed via magnetic resonance imaging (MRI) may contribute to understand motor recovery. This study assessed relationships between standing ability with scES and spared spinal cord tissue characteristics at the lesion site. We hypothesized that the amount of lateral spared cord tissue would be related to independent extension in the ipsilateral lower limb. Eleven individuals with chronic, clinically motor complete SCI underwent spinal cord MRI, and were subsequently implanted with scES. Standing ability and lower limb activation patterns were assessed during an overground standing experiment with scES. This assessment occurred prior to any activity-based intervention with scES. Lesion hyperintensity was segmented from T2 axial images, and template-based analysis was used to estimate spared tissue in anterior, posterior, right, and left spinal cord regions. Regression analysis was used to assess relationships between imaging and standing outcomes. Total volume of spared tissue was related to left (p = 0.007), right (p = 0.005), and bilateral (p = 0.011) lower limb extension. Spared tissue in the left cord region was related to left lower limb extension (p = 0.019). A positive trend (p = 0.138) was also observed between right spared cord tissue and right lower limb extension. In this study, MRI measures of spared spinal cord tissue were significantly related to standing outcomes with scES. These preliminary results warrant future investigation of roles of supraspinal input and MRI-detected spared spinal cord tissue on lower limb motor responsiveness to scES.