404 A Novel Minimally Invasive Porcine Model of Acute Spinal Cord Injury

INTRODUCTION: Spinal cord injury (SCI) animal models often utilize an open surgical laminectomy, which results in animal morbidity and also leads to changes in spinal canal diameter, spinal cord perfusion, cerebrospinal fluid flow dynamics, and spinal stability which may confound SCI research. METHODS: The model was validated in 5 YucatÁn pigs. Each animal underwent MRI and electrophysiology assessment at baseline, immediately after injury, and at experimental endpoint. Under general anesthesia, a kyphoplasty balloon was inserted into the dorsolateral epidural space of the animal's thoracic spine. The balloon was inflated while performing intermittent transcranial motor-evoked potentials (MEPs). Balloon inflation was stopped when MEPs were >80% diminished in the lower extremities. The balloon was maintained at this pressure for 10 minutes, then deflated. RESULTS: MEPs in hindlimb muscles were universally abolished in all animals after injury, while spinally evoked potentials remained unchanged. The MEPs in hindlimb muscles recovered eight days post-surgery. Immediate post-injury 1.5T MRI demonstrated a T2-hyperintense focus within the spinal cord parenchyma at the site of injury in each animal consistent with a mild contusion injury. Endpoint spinal cord histology in each case demonstrated multilobular cystic cavitation at the site of injury along with axonal loss in the dorsal and lateral funiculi. CONCLUSIONS: Imaging, neurofunctional, histologic, and electrophysiologic findings were consistent with a mild compression injury. Balloon inflation pressure, length of time that balloon remains inflated, and speed of inflation may be modified to achieve variations in injury severity and subtype.