Abstract No. 21: Major motor nerve injury following irreversible electroporation (IRE) in a porcine model

Abstract

To determine whether irreversible electroporation (IRE) may be performed safely in close proximity to the sciatic nerve in a porcine model. Single session IRE treatment adjacent to the normal sciatic nerve at the sciatic notch was performed unilaterally in 4 female Yorkshire pigs under general anesthesia and using pancuronium as a paralytic agent. Two to four 19-gauge monopolar electrodes were placed in close proximity to the sciatic nerve under CT guidance. IRE was performed using 1500–1800 V/cm. One of the animals was sacrificed acutely. The other 3 pigs were observed for up to 7 days before they were euthanized for pathologic correlation. The pigs were administered analgesics and encouraged to ambulate in the observation period. Contrast-enhanced CT was performed immediately following IRE, and contrast-enhanced CT or MRI was performed on the day of sacrifice. Gross and microscopic histology of the ablated tissue were evaluated. The closest electrode was placed within 0–5mm of the sciatic nerve in each animal. Maximal dimension of the ablation zone on immediate post-ablation contrast-enhanced CT measured 2.5 cm with 2 electrodes (n=1) and 6.9–7.2 cm (n=3, mean 7.0 cm) with 4 electrodes. Size of the ablation zone decreased to 3.6–6.8 cm (mean 5.3cm) on contrast-enhanced MRI within 2–7 days. Two of the 3 non-acute pigs were unable to ambulate over an observation period of 2–7 days, including one pig euthanized at day 2 post-IRE due to immobility. Histology confirmed injury to the sciatic nerve in the acute and 2 immobile pigs. IRE performed in one animal at 5mm from the sciatic nerve did not result in nerve injury or immobility; in this case, the zone of non-enhancement on post-ablation CT did not extend beyond the nerve. Major motor nerves less than 5 mm from the IRE electrode may be injured and become nonfunctional. Further investigation is warranted to determine the safety parameters of IRE in perineural tissue.