PainUltrastructural evaluation of pulsed radiofrequency and conventional radiofrequency lesions in rat sciatic nerve
Introduction
RF treatments have been used for more than 30 years for a variety of pain syndromes as follows: occipital neuralgia [7], cervical radicular pain [18], [25], intercostal neuralgia [26], lumbar radicular pain [10], mechanical low back pain because of the zygapophyseal joints dysfunction [6], and discogenic pain [8]. In addition, the CRF is used for computed tomography-guided percutaneous cordotomy, extralemniscal myelotomy, and trigeminal tractotomy [12]. In the application of CRF, heat is produced in the tissues surrounding the RF electrode tip [21]. The result is a coagulative necrosis of the targeted tissue that is not conceptually different from other neurolytic procedures designed to destruct sensory pathways for pain relief [16].
The PRF is a newly defined energy type, in which a relatively high voltage is applied intermittently to the neural tissue. Sluijter et al [20] proposed that the effect of PRF is due to the EMF produced during the application. PRF has recently been introduced as an alternative method of pain intervention and is rapidly gaining acceptance because it is an apparently effective therapy that does not cause extensive tissue injury. It has been suggested that PRF might be suitable for use in patients with neuropathic pain in whom the pain could not be controlled by invasive techniques and oral medication [20]. However, the mechanism of therapeutic effect PRF is still controversial.
The purpose of this study was to investigate the effects of PRF on neuronal histopathologic condition and ultrastructure in rat sciatic nerve and to compare with the effects of CRF and low-temperature CRF.
Section snippets
Surgical procedure
Twenty-five male Wistar rats, weighing between 180 and 220 g were used. The rats were anesthetized with ketamine hydrochloride, 100 mg/kg (Ketalar, Eczacıbası, Istanbul, Turkey), and xylazine, 5 mg/kg (Rompun; Bayer, Leverkusen, Germany). All surgical procedures were performed by the same surgeon with the aid of an operating microscope. The right sciatic nerve was used for the surgical procedures. An ECG pad was used as a return electrode for the RF generator and placed on the rat's chest. A
Results
During the experiment, all rats were alive. None of them developed wound infections and autotomy. In the transmission electron microscopic examination of the unmyelinated axons, they were found to be normal ultrastructurally, in all of the groups (Fig. 2, Fig. 3).
In group 1 (control group), nearly all of the myelinated axons were found to be normal, ultrastructurally (Fig. 1).
In group 2 (sham group), most of the myelinated axons were found to be normal; however, in a few of the myelinated
Discussion
PRF has recently been introduced as a nonneurodestructive or minimally neurodestructive alternative to radiofrequency for the management of chronic pain [2], [20]. In particular, recent manuscripts by Van Zundert et al [28], [29] report no side effects in a series of patients treated with percutaneous PRF for chronic cervical and trigeminal pain syndromes. An editorial reviewing the current literature concludes that PRF stimulation of the DRGs is a valid neuromodulation technique that is not
Conclusion
This is the first experimental study showing the ultrastructural effects of PRF on peripheral nerve tissue quantitatively. Ultrastructural analysis was showed significant differences between the PRF and CRF groups. We think that separation in myelin configuration may result in blockage or interruption of the nerve signal through that nerve pathway that may be responsible for reversible neuronal depression. PRF may be used as a test method to decide to make permanent RF lesions if it works.
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2020, BioelectrochemistryCitation Excerpt :Two decades after its conception and despite multiple evidence of its effectiveness [4], the exact mechanism of action of PRF has not been revealed yet. There is evidence that the analgesic effect of PRF is neither related to thermal effects nor to a permanent physical neural damage [6–9]. Currently most studies suggest that PRF induced pain relief takes place through a neuromodulatory-type process that alters the synaptic transmission or the excitability of C fibers [10–12].