Randomized and controlled prospective trials of Ultrasound-guided spinal nerve posterior ramus pulsed radiofrequency treatment for lower back post-herpetic neuralgia

Anatomo-physiological basis and applied techniques of electrical neuromodulation in chronic pain

Chronic pain, a complex and debilitating condition, poses a significant challenge to both patients and healthcare providers worldwide. Conventional pharmacological interventions often prove inadequate in delivering satisfactory relief while carrying the risks of addiction and adverse reactions. In recent years, electric neuromodulation emerged as a promising alternative in chronic pain management. This method entails the precise administration of electrical stimulation to specific nerves or regions within the central nervous system to regulate pain signals. Through mechanisms that include the alteration of neural activity and the release of endogenous pain-relieving substances, electric neuromodulation can effectively alleviate pain and improve patients' quality of life. Several modalities of electric neuromodulation, with a different grade of invasiveness, provide tailored strategies to tackle various forms and origins of chronic pain. Through an exploration of the anatomical and physiological pathways of chronic pain, encompassing neurotransmitter involvement, this narrative review offers insights into electrical therapies' mechanisms of action, clinical utility, and future perspectives in chronic pain management.

Analgesic Treatment Approach for Postherpetic Neuralgia: A Narrative Review

Post-herpetic neuralgia (PHN) is an entity derived from peripheral nerve damage that occurs during the reactivation of the Varicella Zoster Virus (VZV), which manifests itself through pain with neuropathic characteristics. This can prove to be very difficult to manage in the chronic stages of disease reappearance. There currently exists a multitude of treatment alternatives for PHN, however, prevention through the early initiation of antiviral regimens is vital. There are various pharmacological options available, but it is important to individualize each patient to maximize efficacy and minimize adverse effects. Interventional procedures have become a cornerstone in difficult-to-manage cases, and have shown promising outcomes when used in a multimodal approach by experienced specialists. It is necessary to make an objective diagnosis of PHN and start early treatment. Additionally there is current evidence that vouches for interventional therapies as well as individualization, with a clear establishment of therapeutic objectives according to the needs of each patient.

Ultrasound-Guided Selective Pulsed Radiofrequency Treatment of Great Auricular Nerve for Post-Herpetic Neuralgia of the Head and Neck: A Case Report

Objective

The current study aimed to further verify the feasibility of ultrasound-guided selective pulsed radiofrequency (PRF) therapy of greater auricular nerve (GAN) in the treatment of head and neck post-herpetic neuralgia (PHN) by observing the efficacy and safety.

Methods

Under the guidance of high-frequency ultrasound (Frequency: 10 MHz), the GAN was identified by a radiofrequency electrode trocar with a transverse in-plane approach, which was inserted into the GAN, then the inner needle of the trocar was retracted. After adjusting the technical variables (electrode tip temperature: 42°C, output voltage: 60 V, pulse frequency: 2 Hz, pulse width: 22 ms, single duration: 240 s, two times), the radiofrequency electrode placed on the auricle and below the ear for sensory and motor tests began to work.

Results

The pain in the left head and neck of the patient lasted for more than 1 month, we decided to try selective PRF of GAN guided by ultrasound for the first time. Immediately after the treatment, 11-point pain intensity numerical rating scale (PI-NRS) score ranged from 5 to 1. During his hospitalization, mecobalamine and gabapentin were taken instead of opioids. Seven days after the procedure, PI-NRS score was 2, the degree of numbness the patient he felt by himself in the original lesion area relieved from 100% to 40%, the depression module of the Patient Health Questionnaire-9 (PHQ-9) score was from 7 to 5, the Generalized Anxiety Disorder-7 (GAD-7) score from 8 to 4, the range of pain areas was reduced to external auditory tract, and there were no adverse events occurring.

Conclusion

The ultrasound-guided selective PRF treatment of GAN was safe and effective in the improvement of PHN in the head and neck, which is worthy of clinical promotion.

Pulsed radiofrequency inhibits expression of P2X3 receptors and alleviates neuropathic pain induced by chronic constriction injury in rats

Background:

Pulsed radiofrequency (PRF) is a minimally invasive interventional technique that provides a novel and effective treatment strategy for neuropathic pain (NP). PRF is advantageous because it does not damage nerves and avoids sensory loss after treatment. At present, animal studies have demonstrated that PRF is safe and effective for relieving the NP associated with sciatic nerve damage in rats with chronic constriction injury (CCI). However, the mechanism through which this effect occurs is unknown. An increasing body of evidence shows that the expression of the P2X ligand-gated ion channel 3 (P2X₃) receptor is closely related to NP; this study was to investigate whether the expression of this receptor is involved in NP relief due to PRF.

Methods:

A total of 36 healthy adult male Sprague-Dawley (SD) rats were randomly divided into three groups: Sham group, CCI group, and PRF group. The right sciatic nerve was ligated in CCI group and PRF group to establish a CCI model; the right sciatic nerve was separated but not ligated in Sham group. On day 14 after the operation, PRF was administered to the ligated sciatic nerve in PRF group (42°C, 45 V, 2 min). A non-live electrode was placed at the exposed sciatic nerve for the rats in Sham and CCI groups. The hindpaw withdrawal threshold (HWT) and thermal withdrawal latency (TWL) were measured at the right hindpaw at different time points before and after PRF or sham therapy. On day 28 after treatment, the dorsal root ganglion (DRG) and spinal dorsal horn of the right L4–6 were harvested from each group to determine the mRNA and protein levels of the P2X₃ receptor.

Results:

On day 28 after PRF treatment, the HWT (8.33 ± 0.67 g vs. 3.62 ± 0.48 g) and TWL (25.42 ± 1.90 s vs. 15.10 ± 1.71 s) were significantly higher in PRF group as compared to CCI group (P < 0.05). The mRNA expression of the P2X₃ receptor in the DRG in PRF group was 23.7% lower than that in CCI group (P < 0.05), in the spinal dorsal horns in PRF group was 22.7% lower than that in CCI group (P < 0.05). The protein expression of the P2X₃ receptor in the DRG in PRF group was 27.8% lower than that in CCI group (P < 0.05), in the spinal dorsal horns in PRF group was 35.6% lower than that in CCI group (P < 0.05).

Conclusion:

PRF possibly reduces NP in CCI rats by inhibiting the expression of the P2X₃ receptor in the L4–6 DRG and spinal dorsal horns.