The Effect of Prophylactic Local Epidural Steroid Delivery in a Spinal Cord Injury Model

Spinal cord injury during high-risk spinal deformity correction surgery occurs rarely despite best efforts to avoid it. Current neurophysiological monitoring strategies can only report an injury after it happens and some injuries fail to be captured intraoperatively. This catastrophic complication is usually irreversible. Using adult rats and an established spinal cord injury model, the objective of this study was to investigate whether prophylactic delivery of steroids directly to the region of injury via epidural injection, immediately prior to mechanical spinal cord injury, could prevent or reduce the long-term consequences of spinal cord injury. Methods: In adult rats, a previously described model of incomplete spinal cord injury (SCI) was utilized by introducing a size 2-French embolectomy catheter through a T10 laminotomy and compressing the cord by balloon inflation for 6 minutes. There were three study groups: the treatment group with prophylactic local epidural injection of methylprednisone (MP) 30 minutes prior to SCI (“SCI + MP”); the 1st control group with pre-operative normal saline (NS) administered epidurally 30 minutes before SCI (“SCI + NS”); and the 2nd control group with epidural injection of methylprednisone only, without SCI (“MP only”). Rats were evaluated weekly by two blinded evaluators for a period of 6 weeks utilizing the Basso-Beattie-Bresnahan (BBB) standardized behavioral scoring system. Results: The MP only group without SCI recovered from surgery rapidly without any behavioral indication of SCI. There was a significant improvement in average BBB scores in the MP only group at week 2-3 (versus post-operative day 1 [POD1]) in the 3-week data (p< 0.0169). Significant differences in the mean BBB score were determined in the SCI+MP group at weeks 1-3 (versus POD1) in the 3-week data (p< 0.0169). These behavioral improvements were not observed in the SCI+NS group over time. At 3 weeks post-SCI, both the SCI+NS and SCI+MP groups had significantly lower mean BBB scores than the MP only group (p< 0.005). At 6-weeks post-SCI, mean BBB scores were significantly different between the MP only group and the SCI+NS and SCI+MP groups (p< 0.05). Mean BBB scores were significantly higher for the SCI+MP group than for the SCI+NS group at weeks 2-4 (p< 0.05). Six weeks after SCI, the final mean BBB scores were 11.8 for the SCI+MP group versus 0.5 for the SCI+NS group. Conclusion: Rats treated with prophylactic, local, epidural MP prior to mechanical SCI recovered faster and to a significantly greater extent compared to those treated with saline only. Furthermore, epidural MP administration without SCI did not have any appreciable negative effects. Prophylactic treatment of high-risk spinal deformity surgery patients with a high concentration of epidural or intrathecal methylprednisolone may have potential to mitigate SCI severity. This possibility deserves further investigation in animals and human subjects.