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Interv Pain Med
Interv Pain Med
Interventional Pain Medicine
2772-5944
Elsevier

S2772-5944(23)00094-8
10.1016/j.inpm.2023.100262
100262
Technical Note
Modified technique for fluoroscopically guided pudendal nerve block for chronic pelvic pain
Modi Devas J. devasjmodi@gmail.com
a∗
Chazen J. Levi b
Singh Jaspal Ricky c
a NewYork-Presbyterian Hospital at Columbia and Cornell, Department of Rehabilitation and Regenerative Medicine, New York, NY, USA
b Hospital for Special Surgery, Department of Radiology, New York, NY, USA
c Weill Cornell Medicine, Center for Comprehensive Spine Care, Department of Rehabilitation Medicine, New York, NY, USA
∗ Corresponding author. 180 Fort Washington Ave., Harkness Pavilion First Floor, RM 168, New York, NY, 10032, USA. devasjmodi@gmail.com
11 6 2023
6 2023
11 6 2023
2 2 1002628 8 2022
25 5 2023
26 5 2023
© 2023 The Authors
2023
https://creativecommons.org/licenses/by-nc-nd/4.0/ This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
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pmc1 Overview

Pudendal neuralgia is a neuropathic condition characterized by severe pain, frequently seen in pain medicine practices. It is estimated to affect approximately 1 in 100,000 individuals [1]. A variety of advancements have been developed for diagnosis and treatment of chronic pelvic pain, including pudendal neuralgia. A comprehensive assessment, including a thorough history, examination, and imaging is crucial to identify the cause of pelvic pain. MRI imaging can be helpful in identifying inflammation around the pudendal nerve as demonstrated in Fig. 1. However, advanced imaging is often unremarkable and, in this case, a diagnostic pudendal nerve block can be pursued. As described previously in the literature, a pudendal nerve block can provide both diagnostic and therapeutic value. Prior to advancements in fluoroscopic guided techniques, anatomical landmarks were used for pudendal nerve blocks.Fig. 1 AXIAL T2 SPAIR MRI showing asymmetric T2 hyperintensity of the right pudendal neurovascular bundle as it passes the ischial spine, indicative of an inflammatory process, which could clinically correlate with pudendal nerve compression or entrapment.

Fig. 1

The current literature describes a fluoroscopically guided technique that employs a 5–15° ipsilateral oblique angulation of the pelvis, with the patient lying prone. The pudendal nerve block is carried out by advancing the spinal needle to the tip of the ischial spine, where the nerve exits the pelvis [2]. We propose a similar technique under fluoroscopy, with a slight variation in needle positioning based on a CT-guided pudendal nerve block technique and MRI imaging. Fig. 2, Fig. 3 demonstrate the precise needle placement to target the pudendal nerve, approximately 5–10 ​mm anteromedial to the ischial spine [3]. To the best of our knowledge, there is currently no published data on the accuracy of fluoroscopically guided pudendal nerve blocks. However we believe this technique may offer greater accuracy, as it is based on an extrapolation of a CT-guided technique.Fig. 2 Axial CT image with patient in prone position. The needle is positioned deep to the sacrotuberous ligament (purple arrow) to the origin of the pudendal neurovascular bundle (red arrow). Obturator internus muscle (blue arrow), ischial spine (green arrow), gluteus maximus (yellow arrow) are also visualized. (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.)

Fig. 2

Fig. 3 Axial CT images with patient in prone position showing proper needle position deep to the sacrotuberous ligament, at the origin of the pudendal neurovascular bundle. Contrast can be seen extending along Alcock's canal, medial to the right obturator internus (red arrow). (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.)

Fig. 3

2 Anatomy

The pudendal nerve provides both motor and sensory innervation, arising from the S2–S4 sacral nerve roots. It provides sensory innervation to the rectal canal, anus, perineum, and external genitalia. The pudendal nerve arises from the sacral plexus and then passes through the greater sciatic foramen, piercing the sacrospinous and sacrotuberous ligaments. The nerve then reenters through the lesser sciatic foramen and courses through the pudendal canal, also known as Alcock's canal, which is formed by fascia of the obturator internus muscle. This canal carries the neurovascular bundle comprised of the pudendal artery, vein, and nerve before exiting medial to the ischial spine, as illustrated in Fig. 4. The pudendal nerve then divides into various peripheral nerves including the dorsal nerve, inferior rectal nerve, and perineal nerve, providing innervation to the penis or clitoris, external anal sphincter, and bulbospongiosus, ischiocavernosus, and levator ani pelvic floor muscles, respectively [4,5].Fig. 4 Male anatomical illustration of the pudendal nerve and terminal branches. By Mikael Häggström, used with permission. [12].

Fig. 4

3 Patient presentation and diagnosis

Patients commonly present with a prolonged course of pelvic pain, initially having participated in conservative treatment options with pharmacotherapy, botox injections, and/or physical therapy as well as integrative options such as acupuncture without relief. Patient's often will describe no relief from pain in either seated or standing positions. The pain is typically localized over the pubic symphysis with radiation to the genitalia region. Physical exam is often unremarkable, however reproducible pain with palpation over the ischial spine or obturator internus spasm could be indicative of pudendal nerve entrapment [6]. Since pudendal neuralgia can also present with urinary or bowel frequency, urgency, or incontinence, a thorough evaluation with examination and advanced imaging must be performed to exclude other etiologies [7]. The Nantes criteria has been developed to provide five essential findings that is consistent with pudendal nerve entrapment syndrome, one of which is a positive anesthetic block and therefore can be pursued for both diagnostic and therapeutic purposes [8].

4 Technique

The patient is positioned prone and the skin is prepped in a standard sterile manner. The fluoroscope is first positioned to provide an AP view of the pelvis and identify the ischial spine. The fluoroscope is then rotated ipsilaterally, until the ischial spine becomes prominent, approximately 5–15°. The skin overlying the ischial spine is then anesthetized with approximately 2 ​mL of 1% lidocaine (preservative free) administered with a sterile 25 gauge 1.5 inch needle. Using fluoroscopic guidance, a sterile 22 gauge 5 inch spinal needle is then advanced to the tip of the ischial spine, as described in the literature (Fig. 5). Our modified technique involves advancing the needle approximately 5–10 ​mm anteromedially after “walking off” the tip of the ischial spine. A lateral view is then obtained to visualize the needle passing just anterior and medial to the ischial spine through the spinotuberous ligament (Fig. 6). Precise needle placement is then confirmed by administering 1 ​mL of Omnipaque (iohexol) contrast dye through microbore tubing under live fluoroscopy. After confirmation of no intravascular uptake and contrast flow pattern consistent with Alcock's canal, the injectate can be administered (Fig. 7). A solution of 2 ​mL of 2% lidocaine (preservative free) mixed with 2 ​mL of 0.25% bupivacaine, and 1 ​mL of triamcinolone solution (40 ​mg/mL) can be utilized as the injectate.Fig. 5 Ipsilateral oblique view is shown to visualize the ischial spine. Left: Ipsilateral oblique view of approximately 10° with femoral head (red), ilium (yellow), and ischial spine (blue) are visualized. Right: Tip of needle is advanced to the tip of the ischial spine, before advancing medial and anterior to the ischial spine. (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.)

Fig. 5

Fig. 6 Lateral view demonstrating advancement of the needle approximately 5–10 ​mm anterior and medial to the ischial spine (blue). (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.)

Fig. 6

Fig. 7 Lateral view (left) and ipsilateral oblique (right) demonstrating uptake of contrast into Alcock's canal.

Fig. 7

5 Follow up

After performing a pudendal nerve block, the patient is closely monitored in recovery for any complications or adverse effects, including lower extremity weakness, bowel incontinence, bladder incontinence, bleeding, or reaction. The patient is instructed to monitor symptoms, keep track of their pain levels (NRS), and is asked to schedule a follow up appointment after approximately 4 weeks. The patient is advised to resume a pelvic rehabilitation program as tolerable, with a focus on strengthening gluteal, hamstring, and pelvic floor muscles. At follow up encounter, if the patient reported at least >50% in pain relief, a second confirmatory block can be pursued to confirm the pudendal nerve as the source of the patient's pain. Should the patient be interested, they can select to pursue pulsed radiofrequency ablation. Methods that have been described include pulsed radiofrequency ablation that is performed for 240 ​seconds at 42° Celsius [9,10].

6 Discussion

Pudendal nerve blocks for pudendal neuralgia has been described as a safe and effective method for reducing pain for patients. Image guidance allows for visualization of anatomical structures and precise anesthetic delivery. We believe this modified technique allows for better accuracy at targeting the pudendal nerve in Alcock's canal. As visualized on CT/MRI imaging, the neurovascular bundle lies just anterior and medial to the ischial spine. We anticipate this would reduce false negatives rates and improve patient outcomes for patients with true pudendal neuralgia. Further randomized control trials would be required to confirm this hypothesis. Some individuals utilize ultrasound guidance, which can certainly be a safe and effective method at targeting the pudendal nerve. However, this technique may require additional training for individuals that are more proficient with fluoroscopic guidance. A randomized trial from 2012 demonstrated that there were no differences in the degree of neural blockade between ultrasound and fluoroscopic guided techniques. However, the time to complete the procedure under ultrasound was significantly longer [11].

7 Conclusion

We describe a modified fluoroscopically guided pudendal nerve block for patients with pudendal neuralgia. Our technique was extrapolated from CT guided procedures, with an anteromedial placement of the needle in reference to the ischial spine, which may reduce fall negatives from the traditional technique and could improve patient outcomes.

Funding

None.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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