Percutaneous Pulsed Radiofrequency Reduces Mechanical Allodynia in a Neuropathic Pain Model

Abstract

Neuropathic pain is a result of a primary lesion or dysfunction of the peripheral or central nervous system, and its treatment is challenging. Animal models have been helpful in understanding mechanisms of neuropathic pain and in developing new treatment strategies. In this study, we examined the effect of percutaneous pulsed radiofrequency (PRF), which is a minimally invasive pain treatment method, on mechanical allodynia in a neuropathic pain rat model. Neuropathic pain was achieved in a peripheral nerve pain model by performing L5-6 spinal nerve ligation. On the 14th postoperative day, percutaneous PRF was applied to the plantar side of the left rear paw. Animals were evaluated for mechanical allodynia with both dynamic plantar aesthesiometer (DPA) (weight and paw withdrawal time) and von Frey filaments (VF) on the 14th postoperative day and 1, 3, 5, 7, 10, and 14 days after PRF treatment. Experiments were conducted in six groups: Sham-operated+placebo PRF 6 min, sham-operated+PRF 6 min, neuropathic (NP)+2 min placebo PRF, NP+2 min PRF, NP+6 min placebo PRF, and NP+6 min PRF. Allodynia developed in all animals in the NP groups compared to sham-operated animals (P=0.0001). DPA and VF showed that PRF application for 2 min significantly improved allodynia on 1-14th post-PRF day, compared to placebo PRF (P=0.0001). Although DPA (both weight and paw withdrawal time) did not show any therapeutic effect from 6 min PRF application on 1-14th post-PRF days (P=1.00), VF demonstrated transient improvement for the first week, which disappeared on later evaluations of the 6 min PRF group. Percutaneous PRF is an effective treatment option in the NP pain model, and further studies are needed to clarify its underlying mechanisms of action.