Chronic Pelvic Pain: Is Neuromodulation the Solution? 2023

Chronic pelvic pain can be a challenge to treat for many reasons, not least because it manifests in myriad ways, making it difficult even to nail down a definition of the term. The pathology behind chronic pelvic pain (CPP) is equally complex.

The authors of a new literature review comment on the potential consequences of this complex situation. They point out that because CPP is difficult to diagnose, patients are often not evaluated by pain management specialists until they have been unsuccessfully treated by two or more specialists from other fields, typically including gynecology.

At this point, they wrote, “CPP has often evolved into a chronic phase, rendering techniques including physical therapy, nerve blocks, radiofrequency lesions, and pharmacologic options increasingly ineffective. In such patients, neuromodulation may be the last bastion of potentially effective therapy.” Perhaps for that reason, interest in the potential of neuromodulation to treat CPP has increased in recent years. The 2022 narrative review, published in Pain and Therapy, set out to evaluate the state of the latest research on neuromodulation for CPP.¹

The reviewers looked at a variety of neuromodulatory approaches to the treatment of chronic pelvic pain, including:¹

• sacral neuromodulation (SNM)
• conus medullaris stimulation (CMS)
• dorsal root ganglion (DRG) stimulation
• dorsal column spinal cord stimulation (SCS)
• pudendal nerve stimulation (PNS)

Prioritizing newer papers and primary manuscripts wherever possible, the researchers searched PubMed, Medline, SciHub, Cochrane, and Google Scholar for studies on neuromodulation treatments for chronic pelvic pain.

Sacral Neuromodulation

A minimally invasive approach, sacral neuromodulation (SNM) was well documented primarily in the treatment of interstitial cystitis/bladder pain syndrome (IC/BPS), with 15 of 35 studies found in this review limited to this indication. All but one study found improvement in long-term pain outcomes in the majority of patients who had at least one follow-up. While adverse effects were inconsistently reported, researchers did note complications for SNM, including explant from infection, pain at implantation site, poor analgesic efficacy, intolerable paresthesias, lead migration or displacement, lead breakage, and device failure (usually consisting of device malfunction or battery failure).

Conus medullaris stimulation, or CMS, for CPP was described in only one multicenter prospective case study, which involved 27 patients with refractory pudendal neuralgia. Twenty of the 27 subjects progressed to permanent CMS implantation. At 15-month follow-up, the average estimated improvement was 55.5%. Complications were minor, and all patients said they would undergo the procedure again.

Dorsal Root Ganglion Stimulation

DRG stimulation was found to be a promising treatment, with studies finding an average decrease of greater than 50% in visual analog scales (VAS) and numerical rating scales in all multi-patient studies. Patients also reported better function and mobility, as well as improved quality of life.

“While the efficacy of neuromodulation for CPP often depends on adequate lead positioning, a lack of consensus exists with respect to the optimal target and location of leads,” Alan D. Kaye, MD, PhD, told PPM. Dr. Kaye is an anesthesiologist and director of the Pain Program Fellowship at Louisiana State University School of Medicine, editor-in-chief of the journal Pain Physician, and one of the study’s authors. “In this regard, DRG stimulation has been observed to provide significant pain relief for study participants,” he said.

The reviewers found 10 studies evaluating dorsal column SCS for managing CPP. Only one study was an RCT, comparing SCS to DRG stimulation. The others were case reports or case series, totaling 56 patients in all. These studies included patients with different pain etiologies, including irritable bowel syndrome, pudendal neuralgia, post-herniorrhaphy pain, and non-specific pelvic pain. The results suggest that SCS could be a useful therapy, though the researchers found no RCTs comparing SCS to placebo for pelvic pain.

Pudendal Nerve Stimulation

Data was limited for pudendal nerve stimulation as well. The reviewers found only five studies totaling 129 patients: a case series, a case report, two retrospective studies, and one prospective, double-blind crossover trial that compared PNS with sacral stimulation. From this limited data, the authors suggest that PNS “appears to have a positive impact on pelvic pain outcomes.”¹

Practical Takeaways

In their final analysis,¹ the researchers found evidence of benefit for all of the neuromodulation approaches reviewed. However, the data in general were of low quality and limited, particularly regarding study conditions and sample sizes, a finding that was not unexpected.

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