Chronic pelvic pain is a common problem, especially in women, with ratio “2:1” which produces a higher degree of functional and emotional impairment to the patient. Chronic Pelvic Pain (CPP) is a poorly localized pain due to damage of tissue or nerve from inflammation which worsens with odd sitting posture such as leaning back while being seated, prolonged sitting as well as standing and abrupt rising from sitting position [1,2]. 

Due to diverse and complex origin of chronic pelvic pain, it eventually becomes difficult to diagnose and treat this type of pain. The effectiveness of the treatment in patients of chronic pelvic pain corresponds with a change in the VAS score [3].

The Ganglion of Impar (Ganglion of Walther) is a solitary retroperitoneal structure, which is formed by termination of paired sympathetic chains in the sacral region. Blocking the Ganglion Impar attenuates this sympathetically mediated recalcitrant chronic pelvic pain, leading to reduction of opioids consumption, less side effects and an improvement in the patients’ quality of life [4].

A radiofrequency ablation is a minimally invasive procedure that destroys the nerve fibers carrying pain signals to the brain. Radio Frequency Ablation (RFA) of Ganglion Impar is a well-established, drug-free treatment that has been clinically proven to provide safe, effective, lasting relief from chronic pain. Both Thermal Radiofrequency Ablation (TRF) and Pulsed Radiofrequency Ablation (PRF) treatment induce distance-dependent tissue destruction under the stimulating needle. The acute effects of PRF are more reversible and less neurodestructive in nature than the TRF mode, even in normothermia conditions hence PRF is better than TRF. PRF produces a transient inhibition of evoked synaptic activity and classic thermal RF (TRF) produces a lasting inhibition [5,6].

The purpose of this study is to compare the VAS score between Thermal and Pulsed radiofrequency ablation in Ganglion Impar block for treatment of chronic pelvic pain in female patients.

Aims and Objectives

To compare analgesia using VAS score in both the groups over period of 3 weeks.

After obtaining approval from the Institutional ethics committee, CTRI registration number CRTI/2020/10/028306 and written informed consent of the patients, the proposed study was carried out in adult female patients of age groups 18-60 years, visiting the pain clinic for chronic pelvic pain, who had already taken medications for 2 weeks but inadequate benefit was reported by medications and physiotherapy trial.

Source of Data

This study was conducted on patients with chronic pelvic pain at IGMC and associated hospital KNSH for M and Ch SHIMLA with the approval of research and Ethics Committee.

Study Design

This study was randomized, single blinded prospective and controlled study.

Inclusion Criteria

• Patient giving consent to participate in the study

• Female patients with chronic pelvic pain after ruling out any obstetrics and gyanecological cause through specialist opinion and USG or negative diagnostic laproscopy

• Patients above the age of 18 years and below 60 years

• Patients who have had atleast two weeks trial of medications without significant effect

• Patient with normal anatomy for ganglion impar block

Exclusion Criteria

• Patient refusal

• Patients with uncontrolled systemic diseases

• Patients with infection or injury at the injection site

• Patients with coccygectomy

• Allergy to iodine contrast medium

• Hypersensitivity

• Patient with bleeding disorders and the patients on anticoagulants

A total of 30 patients from pain clinic who were suffering from chronic pelvic pain were included after obtaining written consent.

Sample Size Calculation 

The sample size was calculated to be of 15 subjects for each group; this was calculated on the basis of a similar study in chronic pelvic pain patients where the minimum number of patients required were found to be 31, with a power of at least 80% and α of 0.05 while considering VAS score as primary objective. Anticipating loss of subjects during the study, we enrolled 30 patients in our study, 15 in each group.

The patients were divided into 2 groups of 15 patients each using computer generated random numbers:

• Group A: [Group-Thermal RFA] patients were treated with thermal radiofrequency ablation

• Group B: [Group-Pulsed RFA] patients were treated with pulsed radiofrequency ablation

The study was randomized, single blinded prospective and controlled study with follow up done weekly for three weeks either by routine checkup in the pain clinic or through a phone call.

They underwent radiofrequency ablation of Ganglion Impar by trans-sacro-coccygeal technique using C-arm guidance. Patients were made familiar with VAS score. The ganglion impar block was administered in all these patients under all aseptic precautions using C-arm guidance to mark and identify bony landmarks.

Methodology

All patients underwent a routine preanaesthetic checkup. During this, thorough history, general examination, routine investigations of the patients i.e. FBS/RBS, Bleeding Time (BT), Clotting Time (CT) of the patient was carried out.

Pre-procedural assessment of pain was done on the basis of VAS score. After confirmation of inclusion criteria of the patient by the anesthesiologist the procedure was undertaken. Written informed consent was taken from the patient prior to the procedure explaining the various risks and benefits of the procedure. Baseline VAS was recorded prior to beginning the procedure.

A 20-gauge venous access was secured and basic monitors such as noninvasive blood pressure and saturation (SpO₂) probe will be connected. The procedure was carried out with the patient in prone position with pillow under the abdomen to allow flexion of the lumbosacral spine and the lower extrimities rotated internally. 

The procedure was performed using C-arm to identify and mark the essential bony landmarks. Under strict aseptic precautions the saccrococcygeal and gluteal regions were cleaned with savlon and painted with povidone iodine 10%. The area was drapped with sterile towels and the access region was left open. A skin wheal was raised with 1% lidocaine using 25 gauge needle after the identification of the disc in lateral projection. A true lateral image was obtained by superimposing the two greater sciatic notches.

About 22G, 5 cm long with 5mm active tip radiofrequency needle was then introduced from the marked site to pierce the saccrococcygeal joint and position was confirmed after injecting non-ionic dye and needle placement was confirmed by induction of reverse comma sign/“crescent” sign in lateral fluroscopic views. 

A diagnostic block was performed using 1% lidocaine 10ml. After 5 min, patient was ressessed and if the patient consider pain relief of atleast 2 point reduction in VAS scores, the patients were considered candidates for radiofrequency ablation of Ganglion Impar. 

Before radiofrequency ablation was performed, tissue impedence check and motor and sensory tests were done. These comprised tissue impedence <600 Ohm, sensory response <50 Hz and motor response <2 Hz at stimulation intensity between 0.4–0.8 volts. Patients with no significant decrease in VAS score were excluded from this study.

Thereafter radiofrequency ablation was done depending upon the group:

• Group A: Thermal radiofrequency ablation, was done using radiofrequency thermocouple electrode (Cosman Medical Co Inc.) connected to Cosman radiofrequency generator using following parameters: tissue impedance <600 Ohm, sensory response <50 Hz and a motor response <2 Hz at a stimulation intensity between 0.4–0.8 Volts (V) with 3 cycles each 90 seconds apart and temperature ranging from 60-80°C

• Group B: Pulsed radiofrequency ablation, was done using radiofrequency thermocouple electrode using the following parameters: voltage output 45 V; 2 Hz frequency; 20 ms pulses in a one-second cycle, 120 second duration per cycle; impedance range between 150 and 500 Ohms with 3 cycles and a 42°C plateau temperature 

Inj bupivacaine 5mL and inj dexamethasone 2 mg was injected the end of procedure to overcome ablation induced pain and neuritis. Follow up was done after the procedure using VAS score.

Figure 1: 
 

Patients were kept in the recovery room for 2 hours and then sent home with the attendents on the day of the procedure with routine single dose antibiotic prophylaxis, NSAIDS in the form of Tablet Diclofenac 100mg SR for 3 days. Patients were advised to abstain from heavy workload after the procedure. Patient who complained of increase in VAS in between the follow up period were given tablet Pregablin 75 mg H.S. at night as rescue drug.

Follow-up after 24 hours,1 week, 2 weeks and 3 weeks was done either in OPD or telephonically and VAS score was noted.

Failure Cases

Patients who did not achieve a successful block, that is patients in whom there is no decrease in VAS by 2 points after 24 hours of block were dropped from further study; but the number was noted as failure cases and other form of treatment was given.

Visual Analogue Pain Scale 

Employs a 10 cm drawn line with left anchor point descriptor labeled “no pain” and the right sided equivalent labeled “worst possible pain”. It requires patients to mark current pain severity on the continuum. The VAS score is the measured distance from the “no pain” point to the pain estimate (Figure 1).

Statistical Analysis

All the data collected from the patient’s records was transferred into MS Excel sheet for further processing and analysis. Data was further analyzed using standard statistical software. In order to compare results between two study groups, appropriate parametric or non parametric test of statistical significance was used. Probability value (p-value) less than 0.05 was considered statistically significant.

The present study was conducted in prospective, single blind, randomized controlled manner in the Pain Clinic in the Department o Anesthesiology at Indira Gandhi Medical College and Hospital. It comprised of total 30 female patients between age group 30-60 years. Patients were randomly divided into two groups. Patients in Group A(n = 15) were given thermal radiofrequency ablation where as patients in Group B were given pulsed radiofrequency ablation. No patients experienced any interventional failure (inability to obtain proper fluoroscopic view of dye). So, in each group 15 patients were studied.

Table 1: Age Wise Distribution of the Patients

Table 2: Comparison of Pre Procedural VAS Score

Table 3: Comparison of 24 Hours Post Procedural VAS Score

Table 4: Comparison of 1 Week Post Procedural VAS Score

Table 5: Comparison of 2 Week Post Procedural VAS Score

Table 6: Comparison of 3 Week Post Procedural VAS Score

Socio-Demographic Analysis

According to age distribution, in group A, 3(20%) were ≤40 years, 6(40%) were between 41-50 years and 6(40%) were between 51-60 years of age while in group B, 8(53.3%) were ≤40 years, 4(26.7%) were between 41-50 years and 3(20%) were between 51-60 years of age. The p-value was calculated to be 0.159 which was found to statistically non-significant (Table 1).

Mean age (in years) in group A and B was found to be 47.60±6.833 and 42.67±7.807 years respectively. The p value was calculated to be 0.76 which was found to be statistically non-significant (Table 1).

VAS Scale 

Pre-Procedural VAS Score: The mean Pre-procedural VAS score of the patients in Group A was 7.93±0.704 where as mean Pre-procedure VAS score in patients of group B was 8.00±0.655. The p-value was 0.790 which was statistically non-significant (Table 2).

24 Hours Post Procedural VAS Score

The mean 24 Hours Post Procedural VAS Score of the patients in Group A was 2.53±0.516 where as mean 24 Hours Post Procedural VAS Score in patients of group B was 3.53±0.640. The p value was 0.000 which was statistically significant. This showed that mean 24 Hours Post Procedural VAS Score was significantly lower in group A as compared to group B (Table 3).

1 week Post Procedural VAS Score

The mean 1 week Post Procedural VAS Score of the patients in Group A was 2.60±0.507 where as mean 1 week Post Procedural VAS Score in patients of group B was 3.40±0.507. The p-value was 0.000 which was statistically significant. This showed that mean 1 week Post Procedural VAS Score was significantly lower in group A as compared to group B (Table 4).

2 week Post Procedural VAS Score

The mean 2 week Post Procedural VAS Score of the patients in Group A was 2.33±0.507 where as mean 2 week Post Procedural VAS Score in patients of group B was 3.31±0.564. The p-value was 0.000 which was statistically significant. This showed that mean 2 week Post Procedural VAS Score was significantly lower in group A as compared to group B (Table 5).

3 week Post Procedural VAS Score

The mean 3 week Post Procedural VAS Score of the patients in Group A was 2.31±0.415 where as mean 3 week Post Procedural VAS Score in patients of group B was 3.29±0.516. The p value was 0.000 which was statistically significant. This showed that mean 3 week Post Procedural VAS Score was significantly lower in group A as compared to group B (Table 6).

Chronic pelvic pain is associated with burning sensation and intractable pain in pelvic region and sometimes radiating to lower limbs. Treatment options include conservative management using analgesics, opioids, physiotherapy, ganglion impar block using steroids, local anesthetics, neurolytics and radiofrequency ablation. Lim et al. [7] in their study used botulinum toxin Type A to block Ganglion Impar in patients with chronic pelvic pain and found significant reduction in pain by assessing post procedural VAS score.

We conducted a prospective single blinded randomized control study with a calculated sample size of 30 with history of pelvic pain where we compared thermal radiofrequency ablation versus pulsed radiofrequency ablation. No literature is available with similar study design using the above mentioned techniques. We observed satistically significant difference in the pain assessment parameters during immediate and follow up period. Thermal radiofrequency ablation was found to be better as compared to pulsed radiofrequency ablation in management of immediate and chronic pelvic pain. The patients were followed for a period of 3 weeks. Post procedural 24 hours mean VAS score in thermal RFA was 2.53 where as in pulsed RFA group was 3.53 (p value <0.05). The result was comparative in both groups. Reig et al. [8] observed that post lesioning VAS score decresed from 8.2 to 3.7 where he used thermal radiofrequency ablation for the management of chronic pelvic pain. The results were comparable with our study.

The difference in mean VAS score after 3 weeks follow up was clinically significant in thermal radiofrequency ablation group (p value <0.05). In a study conducted by Usmani et al. [9] where they compared conventional RFA with local anesthetic and steroid found that after 3 weeks mean VAS score was 2.00±1.22 (p value<0.001). In their study they also evaluated patients’ satisfaction using excellent good and poor variable in his questionnaire pertaining to pain relief in sitting and standing and analgesic requirement. They further observed that patient satisfaction was more on later weeks i.e. 6th and 12th week as compared to 1st and 2nd week.

Under the light of the above-mentioned results, we can conclude that thermal radiofrequency ablation of ganglion impar for chronic pelvic pain produces prolonged pain free period, better functional capacity and better satisfaction in the patients as compared to patients who were treated with pulsed radio frequency ablation. So, the patients of chronic pelvic pain stand to benefit from thermal radio frequency ablation of ganglion impar. However, more studies need to be conducted with larger sample size and longer and more complete follow up.

Limitation

Our study was limited by the limited amount of research that has been conducted in this field. Very few studies have been conducted which described Ganglion Impar using radiofrequency ablation for chronic pelvic pain. We found no study which compared thermal radiofrequency versus pulsed radiofrequency ablation of Ganglion Impar in patients with chronic pelvic pain. The sample size was low in our study due to the Covid pandemic which affected many patients. Above all our study was dependent on referral of patients from other departments who did not respond to conservative management. Lack of general awareness of pain clinic and procedures and undertreatment of the symptoms also contribute to poor patient compliance.

1. Turchan, A. et al. “Impar Ganglion Block with Combination of Neurolysis Drugs and Radiofrequency Thermocoagulation for Perineal Pain.” Asian Journal of Neurosurgery, vol. 13, no. 3, July–September 2018, pp. 838–841.

2. Thienhaus, O. et al. Classification of Pain. In: Pain Management: A Practical Guide for Clinicians, R.S. Weiner (Eds.), CRC Press, 2002. European Association of Urology Guidelines on Chronic Pelvic Pain.

3. Maigne, J.Y. and G. Chatellier. “Comparison of Three Manual Coccydynia Treatments: A Pilot Study.” Spine, vol. 26, no. 20, 15 October 2001, pp. E479–E483.

4. Marker, D.R. et al. “MR-Guided Perineural Injection of the Ganglion Impar: Technical Considerations and Feasibility.” Skeletal Radiology, vol. 45, no. 5, May 2016, pp. 591–597.

5. Usta, B. et al. “Fluoroscopically Guided Ganglion Impar Block by Pulsed Radiofrequency for Relieving Coccydynia.” Pain Practice, vol. 39, 2010, pp. e1–e2.

6. Bonica, J.J. “The Management of Pain of Cancer.” Journal of the Michigan State Medical Society, vol. 52, no. 3, March 1953, pp. 284–290.

7. Lim, S.J. et al. “Ganglion Impar Block with Botulinum Toxin Type A for Chronic Perineal Pain: A Case Report.” Korean Journal of Pain, vol. 23, no. 1, March 2010, pp. 65–69.

8. Reig, E. et al. “Thermocoagulation of the Ganglion Impar or Ganglion of Walther: Description of a Modified Approach. Preliminary Results in Chronic, Nononcological Pain.” Pain Practice, vol. 5, no. 2, June 2005, pp. 103–110.

9. Usmani, H. et al. “Conventional Radio Frequency Thermo Coagulation versus Local Anesthetic and Steroid Injection for Ganglion Impar Block in Chronic Perineal Pain of Non-oncological Origin.” Journal of Anesthesia and Clinical Care, vol. 1, 2014, article 005.