DSPN which is associated with marked impairment in quality of life due to partly excruciating neuropathic pain on the one hand and painless foot ulcers on the other hand, leading to the greatest morbidity and mortality and resulting in a huge economic burden for diabetes care[4, 20]. Regrettably, the mechanism of diabetic neuropathic pain is complex and there is a lack of effective treatment. At present, (1) lifestyle modification, causal treatment aimed at near-normoglycemia and multifactorial cardiovascular risk intervention, (2) pathogenesis-derived treatment and (3) symptomatic treatment of neuropathic pain are often recommended in the treatment guidelines for DSPN[21], it remains suboptimal because of complexity of symptoms and the long duration of therapy. Therefore, it is very important to find more effective treatment methods for DSPN.
SGB is a frequently used technique for treating chronic pain[22], especially for neuropathic pain and reflex sympathetic dystrophy[23]. The procedure involves injection of local anesthetic in and around the stellate ganglion to temporarily block its function. PRF is a common technique of neuromodulation that has been shown to be effective in regulating neurological function[9]. The RF generator intermittently emits impulse current that is conducted to the needle tip and acts as analgesia near neural tissue through field effects caused by rapid voltage fluctuations. At the same time, the electrode tip temperature was maintained at 42℃without disrupting motor nerve function. Mild temperature energy of PRF therapy did not cause nerve damage and would not produce long-term clinical effects[24], Moor et al. performs SG pulsed radiofrequency to treat cluster headaches (n = 2) and shows that 50%, 22%, and 28% have complete, marked/partial, and no improvement, respectively; through 12 months of follow-up, these reduced to 28%, 37%, and 37%, respectively[25]. In our study, we observed that the significant and total effective rates at 1-week post-procedure were 67.86% and 89.29%, and as time went on, the significant and total effective rates at 24 weeks post-procedure were 17.86% and 32.14%. these findings suggests that the clinical effect of ultrasound-guided SG PRF therapy is time dependent.
The analgesic mechanism of PRF is unclear, and it is currently believed that the analgesia is produced by neuromodulation[9]. Recent studies have shown that PRF results in the induction of c-Fos expression, and changes in the efficacy of synaptic transmission, as well as reduce neuroinflammation and nerve damage[26, 27]. The first case series of the stellate ganglion as an interventional site was conducted in 1991, the authors reported a new technique ,PRF, for endoscopic denervation in a mongrel canine model and demonstrates the safety and reliability of PRF[28]. Subsequent case studies involving the anterior ethmoidal nerve[29], infraorbital nerve[30], mental nerve[31], and caudal epidural[32] also suggests satisfactory pain relief that persisted for 6 months. SG pulsed radiofrequency has proved to get long-term pain relief in various neuropathic pain syndromes (post-mastectomy neuropathic pain syndrome, complex regional pain syndromes, and phantom pain)[2], the exact analgesic mechanism is yet to be known, however, the safety and efficacy of SGB treatment have been demonstrated. Yuanyuan Ding et al. have reported that SG pulsed radiofrequency treatment of facial and upper limb PHN is safe and effective and improves the quality of life of the patients. They also proved that SG pulsed radiofrequency superior to SGB [33], it may be due to the gradual metabolism of local anesthetic drugs over time, however. PRF acts primarily through neuromodulation. The effect of neuromodulation is slow, but it can be maintained for an extended period. In this study, the use of SG pulsed radiofrequency in patients with Painful DSPN significantly decreased the VAS scores, SF-MPQ scores, and TCSS indices during the first week after treatment, and the difference was significant compared with preoperative values, and the duration of the clinical maintenance effect (pain relief) exceeds 24 weeks.
Patients with DSPN not only have physical pain, but also have psychological problems caused by affliction and long-term treatment[3]. Alino et al. have found that SG intervention can effectively relieve symptoms in patients with anxiety disorders, psychological conditions improved in PTSD patients after a period of SBG treatment[34]. Our results also revealed that relevant indicators of health-related quality of life, including SDN, KPS, PDI, and PHQ-9, improved to varying degrees after the treatment with SG pulsed radiofrequency.
SG neurons are surrounded by peripheral satellite glial cells (SGCs), and SGCs are an important component of the nociceptive signaling pathway[35, 36]. Reinauer et al have reported that SGB can improve the neurotrophic status, blocking the vicious cycle of pain[37]. At the same time, it can enhance the defense function and prevent nerve damage[38]. Kim et al. performed SG pulsed radiofrequency treatment under ultrasound guidance in patients with CRPS, 91.7% of patients experienced at least moderate improvement (30% self-described degree of benefit), and the mean hand temperature rose by 1.39 ± 0.96℃ after the procedure[39]. Therefore, we hypothesized that SG pulsed radiofrequency therapy could alleviate a series of neuropathy-associated symptoms.in our study, we observed and recorded patients' subjective sensations, including the degree of perceived pain relief (%), numbness relief (%), and chills relief (%). As a result, the degree of perceived pain relief, chills relief, and numbness relief improved after the procedures. It may suggest that ultrasound-guided SG pulsed radiofrequency therapy can ameliorate pain and other symptoms including chills and numbness.
Our study obtains its strength due to this is the first time that SG pulsed radiofrequency therapy has been applied to the treatment of patients with painful DSPN, providing a new treatment for DSPN. However, there are some limitations. Firstly, this experimental study lacks a blank control group, and a simple longitudinal study lacks some reliability, A randomized controlled trial is needed to verify our hypothesis. Secondly, the sample size is small, more multi-center studies will be required to strengthen the findings of our study. Lastly, further study including more objective measures will be required to validate these observations.