Effects of DRG pulsed radiofrequency parameters on the clinical outcome for battered sensory never syndrome: a prospective, triple-blind, randomized controlled trial

Abstract

Battered Sensory Never Syndrome (BSNS) is a condition characterized by persistent, long-term mechanical compression of the sensory roots, dorsal root ganglia (DRG), and sensory fibers of the spinal nerve roots. This leads to symptoms such as hyperalgesia or allodynia, paresthesia, and radicular pain-like syndromes where pain worsens with weight-bearing or physical activity. High-voltage DRG pulsed radiofrequency (PRF) is effective for BSNS, but optimal treatment parameters for the best clinical efficacy remain undefined. This study aims to compare the clinical outcomes of various PRF temperatures and durations in patients with BSNS. Patients with BSNS were randomized to one of four high-voltage (80 V) PRF parameter groups: 42℃/3min, 42℃/12min, 55℃/3min, and 55℃/12min. The primary outcome measures included the Numerical Rating Scale (NRS) and the Oswestry Disability Index (ODI). The secondary outcome measures included the Hamilton Anxiety Scale (HAMA), the Hamilton Depression Scale (HAMD), the Pittsburgh Sleep Quality Index (PSQI) scores, the effective rate of pain relief, the proportion of patients with a ≥ 50% reduction in ODI score, and medication usage. These were evaluated before PRF and within 12 months after surgery. All patients included in our study had a mean age over 60, with the majority being female. Four patient groups showed significant reductions in NRS, ODI, HAMA, HAMD scores (P < 0.05) and decreased medication use within 12 months post-PRF, with no statistically significant differences between the groups (P > 0.05). The PSQI scores decreased significantly only in the 42 °C/3min group at 1 month,3 and 6 months (P < 0.05), also without intergroup significance (P > 0.05). The subgroup analysis by time and temperature revealed that NRS scores (P = 0.009), the number of patients with effective pain relief (P = 0.039) and ODI reduction ≥ 50% (P = 0.045) 1 month after PRF in the 55℃ group were significantly better than those in the 42℃ group, while no statistically significant difference was found between 3-min and 12-min durations (P > 0.05). High-voltage DRG PRF effectively treats BSNS patients within a treatment duration range of 3 to 12 min. Treatment at 55 °C offers superior pain relief and physical function improvement without neuropathic complications.

Supplementary Information

The online version contains supplementary material available at 10.1038/s41598-026-36277-9.

Introduction

Low back pain (LBP) represents a global health challenge of epidemic proportions. It ranks as the foremost cause of disability worldwide, with a point prevalence of 7.5% and a lifetime prevalence exceeding 80%^1,2. Among patients with chronic low back pain, 10–40% of those undergoing lumbar surgery developed Persistent Spinal Pain Syndrome (type 2)^3,4, which is one of the refractory pain conditions in clinical practice. Formerly known as failed back surgery syndrome, PSPS (type 2) manifests as persistent low back pain after surgery, often accompanied by leg pain, including burning or stabbing pain, hyperalgesia or allodynia, paresthesia, and worsened pain during ambulation and other symptoms^5,6. Its etiology involves multiple factors before, during, and after surgery. Apart from incomplete surgical removal, suboptimal screw-rod positioning, postoperative adhesions, or recurrence, the cause remains unclear in most patients. In 1975, Bertrand, G. and in 1985, H. Waisbrod termed PSPS (type 2) with unclear etiology as “Battered Root Syndrome“^7,8. Clinical observations and studies have revealed the following characteristics in such patients: a mismatch between radicular symptoms and the degree of localized compression seen on imaging; persistence of symptoms after minimally invasive or open surgery, with revision surgery that fails to alleviate or even exacerbates symptoms; and hyperalgesia or allodynia in the lower back, buttocks, or legs, generally unrelated to posture. Previously, due to limited understanding, treatment mainly involved medication and revision surgery, which often resulted in unsatisfactory outcomes. This often leads to anxiety, depression, and sleep disorders, severely impacting patients’ physical and mental health. Based on etiology and pathophysiology, researchers have recently proposed the term “Battered Sensory Nerve Syndrome” (BSNS) and have found that high-voltage pulsed radiofrequency (PRF) modulation applied to the corresponding dorsal root ganglion (DRG) significantly benefits BSNS patients⁹.

Pulsed Radiofrequency (PRF) is a minimally invasive neuromodulation technique currently used in clinical practice for treating neuropathic pain (NPP). It utilizes radio waves to generate an electric field, producing brief electrical stimulation and pulsed currents at the tip of the radiofrequency needle to modulate neural activity and alleviate pain^9,10. The standard PRF protocol operates at an output voltage of 45 V, a pulse frequency of 2 Hz, lasting for 120 s, with the electrode tip temperature maintained below 42 °C¹¹. Advantages include operational simplicity, rare complications, and minimal tissue damage. However, PRF demonstrates only partial efficacy, with overall response rates being low, especially regarding sustained therapeutic effects¹². To enhance treatment effectiveness and prolong the duration of analgesia, researchers have explored more efficient PRF modes and discovered that high-voltage can improve PRF therapeutic outcomes^9,11,13–17. Some studies indicate that increasing voltage and treatment duration can effectively manage pain in patients with zoster-associated pain (ZAP), particularly when the disease duration is short^16,18. Furthermore, studies have confirmed that increasing the PRF treatment temperature to 48 °C and extending the duration to 240 s significantly enhanced the therapeutic efficacy for postherpetic neuralgia (PHN)¹⁹. In summary, key PRF treatment parameters including voltage, temperature and duration still lack standardization and require further investigation.

The parameters for DRG PRF treatment of BSNS have not yet been standardized. The conventional protocol typically employs a pulsed radiofrequency mode at 42 °C with a field strength of 70–80 V for 720 s⁹. However, a subset of patients still experiences suboptimal outcomes with recurrent pain, making it particularly important to further enhance the analgesic efficacy of DRG PRF. In earlier clinical practice, to ensure safety and avoid the risk of nerve damage, the output voltage was set based on the patient’s maximum tolerance level, with attempts to appropriately increase the radiofrequency treatment temperature, not exceeding 55 °C. Under this approach, patients reported broader coverage of painful areas during PRF treatment and expressed higher satisfaction with the therapeutic outcomes compare to precious protocols.

The objective of this study is to examine the efficacy and safety profile of high-voltage pulsed radiofrequency therapy administered at different temperatures and durations for the management of BSNS, with the goal of maximizing therapeutic benefits for patients.

Method

Study design and registration

This is a prospective, triple-blind, randomized controlled trial. The study was approved by the Ethics Committee of the Third Xiangya Hospital, Central South University (No.24859,10.10.2024) and retrospectively registered at chictr.org.cn (ChiCTR2500097038,11.2.2025).

Sample size

The sample size calculation was based on a previous retrospective study⁹ of patients with PSPS (type 2) treated with pulsed radiofrequency and our preliminary experimental results, using the mean NRS score (µ₁ = 3, µ₂ = 3, µ₃ = 1, µ₄ = 3) at one month postoperatively as the primary efficacy endpoint. According to the formula²⁰: , Δ = , = , where n = number of participants required in each intervention group, λ is the non-centrality parameter of the chi-square distribution with k-1 degrees of freedom (where k is the number of groups), obtainable from λ tables, and σ² represents the within-group variance, which is the square of 1.86. The significance level (α) was set at 0.05 (two-sided), and the power (1-β) was set at 0.80. Based on the calculation, 13 patients were required per group. Considering a 10% attrition rate, 15 patients were needed per group, resulting in a total of 60 cases across the 4 groups.

Study population

This study screened and evaluated patients suffered from chronic low back pain and/or leg radicular pain, who were hospitalized in the Pain Department of the Third Xiangya Hospital, Central South University, and a total of sixty BSNS patients were recruited to sign the informed consent form.

The inclusion criteria were as follows: (1) symptom duration ≥ 3 months; (2) age ranging from 18 to 80 years; (3) pain intensity ≥ 5 on the Numeric Rating Scale (NRS); (4) clinical presentation consistent with the diagnostic features of BSNS^9,21,22; (5) presence of asymmetric neuropathic pain symptoms, including hyperalgesia, allodynia, or paresthesia; (6) lumbar disc herniation with significant low back and/or leg pain, but lumbar spine MRI showing no indications for surgery; (7) postoperative lumbar spine patients with no significant recurrence on imaging studies but experiencing either poor clinical outcomes or symptom exacerbation after revision surgery.

Patients were excluded based on the following conditions: (1) coagulation disorders; (2) local infection at the puncture site; (3) spinal infections or spinal tuberculosis; (4) vertebral fractures, intraspinal space-occupying lesions, or cauda equina syndrome; (5) severe cardiac, cerebral, renal, or hepatic dysfunction; (6) psychiatric disorders or intellectual disabilities that affect cooperation with minimally invasive procedures; (7) allergy to radiocontrast agents; (8) multiple sclerosis or malignant neoplasms; (9) inability to comply with postoperative follow-up requirements.

Randomization and blinding

Patients were randomly allocated to four PRF treatment groups through a computer-generated protocol. The groups had different parameters: 42 °C/3min, 42 °C/12min, 55 °C/3min, and 55 °C/12min, with a 1:1:1:1 allocation ratio. Blinding was implemented through sealed opaque envelopes. Prior to the procedure, a technician not involved in the study opened sequentially numbered opaque envelopes that contained group assignments. Until study completion, all patients, operating surgeons, and outcome assessors remained blinded regarding group allocations.

DRG PRF procedure

All procedures were performed by the same surgeon under fluoroscopic guidance. Patients were placed in the prone position with a thin pillow under the abdomen and were connected to a grounding pad. The selection of our target segments is based on a combination of the patient’s clinical symptoms, physical examination findings, and imaging presentation. According to the affected DRG segments, the corresponding puncture site was then selected, and a surface marker grid was placed paravertebrally. Under C-arm fluoroscopy, the puncture site was identified at the targeted intervertebral foramen. The needle trajectory was planned, and skin marking was performed.

Following routine skin disinfection and draping, 1% lidocaine was used to administer local anesthesia. After the anesthetic took effect, a PRF introducer needle (Z-1510-20YN; Aesculap, Shanghai, China) was advanced slowly along the planned trajectory under fluoroscopic guidance. The needle position was confirmed radiographically. On the anteroposterior view, the tip was positioned inferior to the lateral border of the pedicle (Fig. 1A). On the lateral view, it was located in the upper third of the intervertebral foramen (Fig. 1B). A small volume of contrast agent was injected to reconfirm the needle position. The radiofrequency electrode was then connected to the RF generator (R-2000B A1; Beiqi, Beijing, China). Sensory testing was performed at 50 Hz, with the needle position adjusted to reproduce tingling sensations in the affected nerve root region at ≤ 0.5 V. Then, motor testing was conducted at 2 Hz, with muscle twitching required in the corresponding nerve root territory at ≤ 1.0 V. Finally, the technician applied PRF treatment according to the randomly assigned stimulation parameters.

Fig. 1.

Fluoroscopic images of the pulsed radiofrequency puncture needle tip located at the right L4 and L5 dorsal root ganglia. (A) Anteroposterior image, confirms that the needle is located below the lateral edge of the pedicle. (B) Lateral image, used to confirm the depth of the needle and show that the needle has entered the intervertebral foramen. Yellow = pedicle, red = intervertebral foramen.

All groups received treatment at a maximum output voltage of 80 V, frequency of 2 Hz, pulse width of 20 ms, delivered over 3 cycles. Throughout the procedure, the impedance was maintained below 400 Ω. During the temperature elevation, patients initially experienced a sensation of heat or burning in the treatment area, which became tolerable after approximately 10 s. For high-temperature groups, the temperature was gradually increased to 55 °C. Prior to PRF treatment initiation, an appropriate dose of intravenous analgesics was administered to minimize patient discomfort. The radiofrequency generator was operated by a specialized technician, and the display monitor was concealed from both the patient and the qualified physician. To consolidate therapeutic efficacy, a second session of DRG PRF treatment with identical parameters was typically performed after a one-week interval, subject to the patient’s consent.

Outcome assessment and follow-up

Follow-up evaluations were conducted by non-surgical team members. In light of the fact that BSNS patients typically present with activity-induced pain, and considering that prolonged pain and repeated treatments may contribute to issues such as anxiety, depression, and insomnia, we have stratified the follow-up evaluation metrics into primary and secondary outcome measures^23,24.

Primary outcome measures included: (1) pain intensity, assessed using the Numeric Rating Scale (NRS)²⁵ (0 = no pain, 10 = unbearable pain); (2) physical function, evaluated with the 10-item Oswestry Disability Index (ODI)^25–27questionnaire (range 0-100; 0–20: minimal disability, 21–40: moderate disability, 41–60: severe disability, 61–80: crippling back pain, 81–100: bed-bound or exaggerating symptoms).

Secondary outcome measures included: (1) anxiety, measured using the Hamilton Anxiety Rating Scale (HAMA)²⁸ (14 items, total score 0–56; <7: no anxiety, 7–13: mild anxiety, 14–28: moderate anxiety, ≥ 29: severe anxiety); (2) Depression, assessed with the Hamilton Depression Rating Scale (HAMD)²⁸ (17 items, total score ≤ 7: normal, 17–24: mild to moderate depression, ≥ 24: severe depression); (3) Sleep quality, evaluated using the Pittsburgh Sleep Quality Index (PSQI)^28,29 (total score 0–21; 0–5: good sleep, 6–10: fairly good sleep, 11–15: general sleep quality, 16–21: poor sleep quality). Assessments were performed preoperatively, 1 day after the first procedure, and at the bedside before discharge. (4) response rate for improvement in pain intensity; (5) the proportion of patients achieving ≥ 50% reduction in ODI scores; (6) medication usage; (7) the number of PRF sessions administered. All complications and adverse events such as local infection, nerve injury, and localized hematoma were recorded. Telephone follow-ups were conducted at 1 week, 1 month,3 months, 6 months and 12 months after discharge.

Statistical analysis

Continuous variables were presented as mean ± standard deviation and analyzed using t-test or ANOVA. Categorical data were expressed as frequencies and compared using χ² test or Fisher’s exact test. Statistical significance was set at P < 0.05. All statistical analyses were performed using Prism 9.0 software (GraphPad, San Diego, CA, USA).

Results

From April 2023 to June 2025, this study initially screened 87 patients with chronic low back pain and/or leg radicular pain. Among these, 60 patients who met the inclusion criteria and provided informed consent were randomly assigned to one of the four treatment groups. Two patients from each group withdrew from follow-up because they opted for alternative surgical interventions. Therefore, the final cohort consisted of 52 BSNS patients for analysis (Fig. 2).

Fig. 2.

Flowchart of study design.

Baseline characteristics

Demographic and clinical characteristics of the patients in each group are summarized in Table 1. The enrolled BSNS patients were characterized primarily by radiating lower limb pain, some patients also presented with concurrent low back pain, with a mean disease duration exceeding 12 months in each group. And all patients included had a mean age over 60, with the majority being female. The mean ID-Pain score upon admission was greater than 2, suggesting the presence of neuropathic pain. Pain intensity was moderate to severe, as reflected by total preoperative Short-Form McGill Pain Questionnaire (SF-MPQ) scores of 10.5 ± 3.3, 9.9 ± 4.5, 8.4 ± 2.8, and 8.2 ± 2.2, respectively. These scores indicate substantial impairment in physical function, mood, and sleep. The mean ODI scores (> 21 points) across all groups indicated at least a moderate level of disability. Additionally, 48% (25/52) of patients exhibited potential anxiety, 63% (33/52) showed signs of potential depression, and 58% (30/52) had fair or poor sleep quality. No statistically significant differences were observed among the four groups in terms of age, gender distribution, disease duration, pain laterality, affected segments, comorbidities, or baseline pain-related measures (P > 0.05).

Table 1.

General characteristics of BSNS patients who received pulsed radiofrequency therapy for the dorsal root ganglion.

Characteristics	42℃/3min (n = 13)	42℃/12min (n = 13)	55℃/3min (n = 13)	55℃/12min (n = 13)	P Value
Age (mean ± standard deviation, years)	64 ± 13	61 ± 16	64 ± 9	62 ± 10	0.829
Sex (male/female)	3:10	5:8	6:7	2:11	0.307
Pain duration (median, range, months)	48 (3-360)	12 (3-120)	36 (3-120)	72 (3-156)	0.083
Side (n, %)					0.080
Left	4 (30.8)	3 (23.1)	8 (61.5)	5 (38.5)
Right	5 (38.5)	8 (61.5)	4 (30.8)	2 (15.4)
Bilateral	4 (30.8)	2 (15.4)	1 (7.7)	6 (46.2)
Dermatome (n, %)					0.967
L3	1(7.7)	1(7.7)	1(7.7)	2 (15.4)
L4	12(92.3)	10(76.9)	11(84.6)	12(92.3)
L5	9(69.2)	11(84.6)	12(92.3)	9(69.2)
PSPS (type 2) (n, %)	5 (38.5)	3 (23.1)	5 (38.5)	4 (30.8)	0.811
Low back pain	6 (46.2)	4 (30.8)	3 (23.1)	5 (38.5)	0.637
Hypertension (n, %)	6 (46.2)	4 (30.8)	5 (38.5)	6 (46.2)	0.831
Diabetes (n, %)	2 (15.4)	3 (23.1)	1 (7.7)	4 (30.8)	0.480
Heart disease (n, %)	2 (15.4)	2 (15.4)	1 (7.7)	2 (15.4)	0.920
Preoperative pain severity (mean ± standard deviation)
ID-Pain scores	2.6 ± 1.0	2.4 ± 0.8	2.3 ± 0.8	2.2 ± 0.8	0.576
SF-MPQ scores
Sensory items	5.7 ± 1.5	5.6 ± 1.5	5.1 ± 1.5	5.3 ± 1.3	0.657
Emotion items	4.8 ± 2.0	4.3 ± 3.2	3.3 ± 2.3	2.8 ± 1.1	0.111
Total scores of pain	10.5 ± 3.3	9.9 ± 4.5	8.4 ± 2.8	8.2 ± 2.2	0.196
ODI (mean ± standard deviation)	31.4 ± 7.6	26 ± 8.7	25 ± 8.7	23.8 ± 7.0	0.126
Possibly anxious (n, %)	7 (53.8)	7 (53.8)	7 (53.8)	4 (30.8)	0.556
Possibly depressed (n, %)	10 (76.9)	10 (76.9)	8 (61.5)	5 (38.5)	0.135
Poor sleep (n, %)	8 (61.5)	8 (61.5)	8 (61.5)	6 (46.2)	0.814
PRF frequency (median, range, times)	2 (1–3)	2 (1–3)	2 (1–3)	2 (1–3)	0.362

PSPS, Persistent Spinal Pain Syndrome, ID-Pain scores Neuropathic Pain Scale scores, SF-MPQ Short-Form McGill Pain Questionnaire, ODI Oswestry Disability Index, PRF pulsed radiofrequency.

Primary outcome measures

Pain intensity

No statistically significant differences in preoperative NRS scores were observed among the groups (P > 0.05). Postoperatively, NRS scores were significantly reduced at all time points compared to preoperative baselines within each group (P < 0.0001). However, no statistically significant differences were detected between the groups at any time point (P > 0.05) (Fig. 3A).

Fig. 3.

Comparison of changes in primary outcome measures among BSNS patients within 12 months after DRG PRF with different parameter groups. (A) NRS score, (B) ODI score(C) HAMA score (D) HAMD score (E) PSQI score. ANOVA analysis of variance: *p < 0.05; **p < 0.01; ***p < 0.001, ****p < 0.0001, ns: P > 0.05. NRS, Numeric Rating Scale; ODI, Oswestry Disability Index; HAMA, Hamilton Anxiety Rating Scale; HAMD, Hamilton Depression Scale; PSQI, Pittsburgh sleep quality index.

Physical function

Postoperative ODI scores demonstrated a significant reduction within each group at all assessed time points compared with preoperative baselines (P < 0.05). However, no statistically significant differences were observed among the groups at any time point (P > 0.05) (Fig. 3B).

Secondary outcome measures

Anxiety levels

Postoperative HAMA scores decreased significantly compared to preoperative baseline values in all four groups. Specifically, the 42 °C/3min, 42 °C/12min and 55 °C/3min PRF groups exhibited significant reductions (P < 0.05) within 12 months after surgery. In the 55 °C/12min PRF group, significant reductions (P < 0.05) were seen at 1 week ,1 month and 3 months postoperatively. However, no statistically significant differences were observed in HAMA scores among the four groups at any time point (P > 0.05) (Fig. 3C).

Depressive symptoms

Postoperative HAMD scores showed significant reductions from preoperative baseline, with statistically significant differences (P < 0.05) observed within 6 months after surgery in the 42 °C/3min PRF group and at all time points in the 55 °C/3 min and 55 °C/12 min PRF groups. No statistically significant differences were found among the four groups at any time point (P > 0.05) (Fig. 3D).

Sleep quality

No statistically significant differences in preoperative PSQI scores were observed among the groups (P > 0.05). Postoperative PSQI scores decreased from preoperative baselines in all four groups; however, statistically significant reductions (P < 0.05) occurred only in the 42 °C/3min PRF group at 1 month, 3months and 6 months postoperatively. No statistically significant intergroup differences were found at any time point (P > 0.05) (Fig. 3E).

Medication usage in the four groups

The number of patients using medications decreased following discharge in all groups. No statistically significant intergroup differences were observed in the use of calcium channel blockers (pregabalin or gabapentin) (Table 2) or nonsteroidal anti-inflammatory drugs (NSAIDs) (Table 3) (P > 0.05).

Table 2.

The usage of calcium ion channel blockers (n, %).

	42℃/3min	42℃/12min	55℃/3min	55℃/12min	P Value
Discharge	7 (53.8)	8 (61.5)	7 (53.8)	8 (61.5)	0.957
1 month	0 (0)	4 (30.8)	1 (7.7)	4 (30.8)	0.077
3 months	0 (0)	1 (7.7)	0 (0)	2 (15.4)	0.184
6 months	0 (0)	1 (7.7)	0 (0)	2 (15.4)	0.184
12 months	0 (0)	1 (9.1)	0 (0)	1 (11.1)	0.499

Table 3.

The usage of NSAIDs (n, %).

	42℃/3min	42℃/12min	55℃/3min	55℃/12min	P Value
Discharge	8 (61.5)	4 (30.8)	6 (46.2)	5 (38.5)	0.435
1 month	0 (0)	0 (0)	2 (15.4)	1 (7.7)	0.184
3 months	0 (0)	0 (0)	0 (0)	0 (0)	/
6 months	1 (8.3)	0 (0)	0 (0)	0 (0)	0.168
12 months	1 (11.1)	0 (0)	0 (0)	0 (0)	0.157

NSAIDs Non-Steroidal Anti-Inflammatory Drugs.

Subgroup analysis by temperature and duration

We compared the efficacy between the 55 °C PRF groups (3 min and 12 min) and the 42 °C PRF groups (3 min and 12 min). At 1 month postoperatively, the NRS scores in the 55 °C PRF group (1.23 ± 0.20) was significantly lower than that in the 42 °C PRF group (2.46 ± 0.41) (P = 0.009) (Fig. 4A). Additionally, 92.3% of patients in the 55 °C PRF group achieved clinically meaningful pain relief (≥ 50% reduction), a rate significantly higher than that in the 42 °C PRF group (65.4%, P = 0.039) (Fig. 4B). Furthermore, a significantly higher proportion of patients in the 55 °C PRF group exhibited ≥ 50% reduction in ODI scores compared to the 42 °C PRF group (76.9% vs. 46.2% ; P = 0.045)(Fig. 4C). However, no statistically significant differences were observed between the 3 min and 12 min PRF groups (each at 42 °C and 55 °C) in any of outcome measures (P > 0.05) (Fig. 5A-C).

Fig. 4.

Efficacy comparison between 42 °C (3 min + 12 min) and 55 °C (3 min + 12 min) PRF groups. (A). The NRS scores within 12 months, the 55 °C PRF group was significantly lower than that of the 42 °C PRF group at 1 month postoperatively. Unpaired Student’s t-test: **p < 0.01. (B) the number of patients with effective treatment 1 month after PRF. Fisher’s exact test: *p < 0.05. (C) the number of patients with ODI reduction ≥ 50% one month after PRF. Fisher’s exact test: *p < 0.05. NRS, Numeric Rating Scale; Effective treatment: NRS > 50% reduction; ODI, Oswestry Disability Index.

Fig. 5.

Efficacy comparison between 3 min (42℃+55℃) and 12 min (42℃+55℃) PRF groups. None statistical significance was found in the NRS scores within 12 months (A), one month after PRF, the number of patients with effective treatment (B), the number of patients with ODI reduction ≥ 50% (C). NRS, Numeric Rating Scale; Effective treatment: NRS > 50% reduction; ODI, Oswestry Disability Index.

Adverse events

No severe adverse events occurred in any group. A small number of patients reported transient pain during the testing procedure, but no procedure discontinuation was required. No procedure-related complications or adverse events including local infection, nerve injury, or hematoma were observed in any group after treatment.

Discussion

BSNS represents a clinically refractory form of neuropathic pain (NPP) characterized by both central and peripheral sensitization. Although DRG PRF has demonstrated significant analgesic effects, achieving long-term efficacy remains challenging. Pain often gradually recurs within months after treatment, albeit generally at lower intensity than before. If pain relapses, patients may require repeated DRG PRF treatments to maintain therapeutic benefits. Therefore, enhancing the efficacy of DRG PRF and prolonging its analgesic duration while ensuring safety constitute urgent clinical priorities.

Researchers have investigated various radiofrequency voltages and durations on the efficacy of PRF treatment. A randomized controlled study found that PRF at 65 V provided better pain relief, improved quality of life, and higher patient satisfaction at 12 months postoperatively, through comparing three groups of PHN patients who received thoracic DRG PRF at different voltages (45 V, 55 V, and 65 V)¹⁵. A similar analysis of various PRF parameters in acute ZAP demonstrated that the high-voltage group (76.50 ± 5.61 V) had lower pain scores, better sleep quality, and reduced medication requirements compared to the standard voltage group (47.73 ± 2.45 V)³⁰. Another retrospective study showed that high-voltage, long-duration PRF effectively treated acute ZAP and yielded better outcomes when applied repeatedly¹⁸. Currently, high-voltage, long-duration PRF has been widely used as a minimally invasive interventional treatment for various NPP conditions including trigeminal neuralgia, PHN, lumbosacral radicular pain, and glossopharyngeal neuralgia. This approach has shown satisfactory therapeutic outcomes^10,11,31,32. In our study, all four groups received high-voltage PRF (80 V). Although the treatments differed in temperatures and durations, all groups showed significant improvement compared to preoperative assessments, with no statistically significant differences observed between groups. The results are consistent with previous findings, demonstrating that high-voltage DRG PRF significantly alleviates pain, improves physical function, and reduces anxiety and depression in BSNS patients. Nevertheless, the improvement in sleep quality was not significant, possibly because most of our patients were elderly and had chronic sleep problems unrelated to pain.

The duration of individual PRF sessions and the number of treatment repetitions are adjustable parameters in therapy. Studies have suggested that extending PRF treatment time to 180s³³, 240s¹³, 360s³⁴, 600s³⁵, or 900s³¹ can yield better analgesic effects compared to the classical standard treatment time of 120s. The principle for determining the number of repetitions is as follows: if the duration of an individual session is relatively short (e.g., 120s), the treatment may be repeated three times³⁶; whereas for longer sessions (e.g., 600s), a single application may suffice without repetition. In our study, no significant difference in therapeutic outcomes was observed between the 3-min and 12-min PRF groups at 12 months postoperatively. Extending the duration of individual PRF sessions did not result in superior therapeutic outcomes. This finding may be related to the desensitization phenomenon as reported by Yuan et al.¹⁹, which occurs within 60 s of PRF application in clinical practice.

The mechanism of PRF remains incompletely elucidated, primarily encompassing two aspects^37,38: Firstly, the thermal effect. During conventional PRF treatment, the temperature is controlled to remain below 42 °C. This temperature range is insufficient to induce protein coagulation, thereby avoiding disruption of signal transduction in nociceptive C-fibers and also preventing adverse effects on larger motor nerve fibers. As a result, this effectively minimizes thermal damage to tissues. Secondly, the electric field effect. PRF generates an extremely high electric field intensity at the electrode tip (in contrast to the low or moderate field strengths present in most target tissues under physiological conditions). This high-intensity electric field can induce the transmembrane potentials in tissue cells. Prolonged alterations in transmembrane potential may further lead to changes in membrane potentials at synapses, thereby modulating synaptic signal transmission. This mechanism can reverse the abnormally enhanced synaptic transmission observed in NPP, ultimately achieving analgesic therapeutic effects. The question of whether PRF efficacy is primarily determined by the electric field effect or the thermal effect of current remains controversial. Some studies have reported a positive correlation between field strength and treatment outcomes during PRF, suggesting that both increasing temperature and raising voltage can enhance field intensity, with high-voltage PRF demonstrating stronger analgesic effects³⁹. In our study, subgroup analysis by temperature showed that the 55 °C PRF group achieved significantly better NRS scores, higher rates of effective pain relief, and greater proportions of patients with ≥ 50% reduction in ODI scores at 1 month postoperatively, compared to the 42 °C PRF group. Overall, all four high-voltage PRF groups (42 °C/3min, 42 °C/12min, 55 °C/3min, 55 °C/12min) demonstrated favorable therapeutic outcomes. These included significant pain relief, marked improvement in physical function, and notable alleviation of anxiety and depression symptoms. No statistically significant differences were observed among the groups. Thus, effective treatment can generally be achieved when a strong field effect is maintained. Based on this, we propose that the field effect plays a dominant role in determining PRF therapeutic efficacy.

The BSNS patients included in our study primarily exhibited lower limb radicular pain, with some patients in each group also experiencing concurrent low back pain. During the research period, all patients underwent DRG PRF surgical treatment. We observed that patients with low back pain symptoms also experienced some degree of relief. We analyzed that this may be related to the anatomical location of the DRG. When pulsed stimulation is applied at the DRG site, it likely affects both the adjacent medial and lateral branches of the dorsal rami. Additionally, the electric field generated by PRF may influence the DRG and its central projections, potentially alleviating not only leg pain but also indirectly reducing some associated referred low back pain by modulating central sensitization or affecting pain transmission pathways.

PRF delivers a low-energy electrical field in rapid pulsations to target nervous tissue⁴⁰. In PRF, because the pulse duration is only a small percentage of the time between pulses, the average tissue temperature rise for the same RF voltage is much less for PRF than for RF. The biological changes in tissue during PRF may result from thermal effects, high-intensity electric fields, or a combination of both. The heat generated during the pulses depends on power deposition, which is related to pulse frequency and pulse width, though the extent of thermal effects remains uncertain. This also represents the innovation of this study, which for the first time combines the temperature and time parameters of DRG PRF (Pulsed Radiofrequency), particularly by deviating from the conventional PRF temperature to explore the impact of these PRF treatment parameters on the clinical outcomes of BSNS patients in a preliminary manner. In the high-temperature group, the radiofrequency temperature was gradually increased. During the treatment, patients reported a tolerable sensation of warmth in the original pain area when the temperature reached 55 °C. Prior to PRF initiation, appropriate intravenous analgesics were administered to minimize discomfort. Electrocardiographic monitoring during the procedure showed no abnormal increase in blood pressure or heart rate. Studies have reported that nerve conduction block occurs in larger nerve fibers at 41–45 °C; in thinner Aδ and C fibers, it occurs at temperatures around at 60 °C. Nerve damage begins to occur at 70–75 °C. Furthermore, temperatures above 85 °C cause non-selective destruction of all nerve fibers¹⁹. Temperature elevation to 48 °C appears to boost PRF efficacy in PHN management¹⁹. Importantly, while PHN patients experience burning pain that could heighten sensitivity to heat, 48 °C remains a well-tolerated and viable option in practice. In this study, the maximum temperature during PRF treatment was set to 55 °C, with a pulse width not exceeding 20ms, and no manifestations of nerve damage were observed postoperatively.

These findings suggest that higher-temperature DRG PRF may enhance neuromodulation without structural injury, supporting its use particularly in patients with refractory BSNS. We hypothesize that elevating the temperature not only augments the thermal effect of the radiofrequency but also potentiates the accompanying field effect.

Our study has several limitations. First, it was a single-center study with a small sample size, which may affect the reliability of the results. Second, the majority of participants included in our study were elderly individuals, who often experience multiple pain conditions due to various comorbidities, including diabetes, potentially serving as confounding factors. Finally, the stratification of temperature and duration into only two levels each, without finer gradations, may have limited the study’s conclusions to some extent. We anticipate that future large-scale, multicenter randomized controlled trials with more refined subgroup analyses will help further elucidate the optimal treatment parameters for DRG PRF in managing BSNS.

Conclusion

High-voltage DRG PRF effectively treats BSNS patients with a treatment duration ranging from 3 to 12 min. Notably, compared to the standard PRF temperature of 42 °C, increasing the temperature to 55 °C can more effectively alleviate pain and improve physical function in BSNS patients, with no complications related to neurological injury.

Supplementary Information

Below is the link to the electronic supplementary material.

Author contributions

Q. W., methodology, data collection, data analysis, visualization, writing original draft. R. H., conceptualization, methodology, data analysis. R. H., investigation, methodology, data collection. Y. N., H.Z., methodology, data collection. D. H., conceptualization, supervision, project administration. Y. H., conceptualization, project administration, methodology, visualization, manuscript review & editing, manuscript revision. Q. D., conceptualization, project administration, methodology, data analysis, visualization, writing original draft, manuscript review & editing, manuscript revision.

Funding

This research was funded by the National Natural Science Foundation of China (82271512 to D.H.) and the National Natural Science Foundation of China for Young Scientists (82401735 to Y.H.).

Data availability

The datasets generated during and/or analyzed during the current study are available from the corresponding author on reasonable request.

Declarations

Competing interests

The authors declare no competing interests.

Ethical approval

The study was conducted in accordance with the Declaration of Helsinki and approved by the Ethics Committee of The Third Xiangya Hospital, Central South University (No.24859,10.10.2024). The trial was retrospectively registered at chictr.org.cn (ChiCTR2500097038,11.2.2025).