Irreversible electroporation in the epidural space of the porcine spine: Effects on adjacent structures

Purpose: To determine the effects of irreversible electroporation (IRE) on the neural tissues after ablation in the epidural space of the porcine spine. Materials and Methods: The institutional animal care and use committee approved this study. With the IRE electrode positioned in the right lateral recess of the spinal epidural space, 20 IRE ablations were performed with computed tomographic (CT) guidance by using different applied voltages in four animals that were euthanized immediately after magnetic resonance (MR) imaging of the spine, performed 6 hours after IRE (terminal group). Histopathologic characteristics of the neural tissues were assessed and used to select a voltage for a survival study. Sixteen CT-guided IRE ablations in the epidural space were performed by using 667 V in four animals that were survived for 7 days (survival group). Clinical characteristics, MR imaging findings (obtained 6 hours after IRE and before euthanasia), histopathologic characteristics, and simulated electric field strengths were assessed. A one-way analysis of variance was used to compare the simulated electric field strength to histologic findings. Results: The mean distance between the IRE electrode and the spinal cord and nerve root was 1.71 mm 6 0.90 and 8.47 mm ± 3.44, respectively. There was no clinical evidence of paraplegia after IRE ablation. MR imaging and histopathologic examination showed no neural tissue lesions within the spinal cord; however, five of 16 nerve roots (31.2%) demonstrated moderate wallerian degeneration in the survival group. The severity of histopathologic injury in the survival group was not significantly related to either the simulated electric field strength or the distance between the IRE electrode and the neural structure (P >05). Conclusion: Although the spinal cord appears resistant to the toxic effects of IRE, injury to the nerve roots may be a limiting factor for the use of IRE ablation in the epidural space.