1473. An Animal Model of Spinal Cord Injury Demonstrating Reproducible Cavitation Following Minimally Invasive Epidural Compression

Authors: Patricia Leigh Zadnik Sullivan; Ahmed AlBayar, MD; John Arena, BS; Jake Budlow, BS; Victoria Johnson; D. Kacy Cullen, PhD; Douglas Smith, MD; Ali Ozturk (Philadelphia, PA)

Introduction: In spinal cord injury (SCI), following the initial impact or injury to the cord, progressive cell death can lead to a cystic cavity. We describe a minimally invasive animal model of SCI resulting in gross cavitation of the spinal cord after epidural compression. Unlike other SCI models, this method does not necessitate a laminectomy at the site of injury to create the lesion and thus does not decompress the canal simultaneously. Methods: All experiments were conducted in accordance with the Institutional Animal Use and Care Committee. A partial laminectomy was made at the L3/4 level in 14 female adult Sprague-Dawley rats. A 2F Fogarty catheter (Edwards Lifesciences) was inserted into the epidural space and advanced to the mid-thoracic spine, then inflated with 200 m L of ambient air for 5 minutes. Animal bladder function and weight were observed for 2 weeks, and ambulatory measures were recorded via Basso, Beattie and Bresnahan (BBB) score. Histopathologic characterization of axial sections at the epicenter, rostral and caudal to the lesion was performed with hematoxylin and eosin staining and immunohistochemistry (IHC) labeling of IBA-1 and GFAP. Results: All animals demonstrated significant impairment in hindlimb function postoperatively. Gross pathological analysis revealed cavitating lesions in the spinal cord. Axial sections rostral to the injury demonstrated central cavitation, and tissue from the epicenter of the injury demonstrated extensive necrosis. IBA-1 and GFAP IHC demonstrated extensive microglial activation and reactive astrogliosis surrounding the cavitation, consistent with pathology seen in human glial scar post SCI. Conclusion: Epidural compression with a Fogarty balloon generates a reproducible spinal cord injury in rats. The resultant injury model replicates elements of human SCI, including ambulatory impairment, cavitation and microglial and astrocyte activation.