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19 Articles in Volume 19, Issue #6
Arthrofibrosis: Targeting Hormones after Childbirth to Relieve Frozen Shoulder, Inflamed Joints
Can CGRP Help Clarify Why Migraine Is More Common in Women?
Case Report: Managing Chronic Pelvic Pain in Men
CGRP Monoclonal Antibodies for Chronic Migraine: Year 1 of Clinical Use
Chronic Pelvic Pain as a Form of Complex Regional Pain Syndrome
Correspondence: Continuing the “Pain Specialist” Dialogue
Endometriosis and its Misunderstood Etiology
Evolving Management Strategies for Osteoarthritic Pain
Gamma PEMF Therapy: A Pilot Study For Its Use in Managing Opioid Addiction
Guest Editorial: Sex Differences in Pain
How to Provide Effective Pain Management to LGBTQ Individuals
Interscalene Peripheral Nerve Stimulation for Post-Operative Chronic Shoulder Pain
New ICD-11 Codes Set to Improve Pain Care in the Primary Setting
Perspective: Could NGF Antagonists Be the Safest, Most Efficacious Class of Drug We Have to Treat Pain?
Rheumatoid Arthritis and Cognition: Is There a Genetic Link?
Targeting Nerves Provides Alternative to Opioids for Joint Arthroplasty
The Sex Question in Primary and Pain Care
What is capsaicin’s role in treating osteoarthritis?
When Pain Clinicians Have to Be the Villain: Communication Strategies to Bridge the Divide

Chronic Pelvic Pain as a Form of Complex Regional Pain Syndrome

Could chronic pelvic pain be treated in a similar manner to CRPS? The authors made a case based on clinical experience.
Pages 50-52

Chronic pelvic pain remains a challenging diagnosis and condition to treat. It tends to be a diagnosis of exclusion characterized by pain that has been continuous or recurrent for at least 6 months and is incumbent of a wide variety of conditions, such as prostadynia, vulvodynia, pudendal neuralgia, interstitial cystitis, coccygodynia, and chronic post-surgical pain to name a few.1 There are many parallels between the characterizations and symptoms of chronic pelvic pain (CPP) and complex regional pain syndrome (CRPS), as well as the response to treatment, that has led to the belief that perhaps CPP may indeed be a form of CRPS. This idea was first introduced by Janicki in 2003, when he noted that both subsets of patients report allodynia and hyperesthesia.2 However, this theory has not gained widespread adoption.

Part of the dilemma in characterizing CPP as CRPS is the medical community’s inability to satisfy the requirements of the Budapest criteria (typically used in the diagnosis of CRPS) by visualizing changes in the patient’s temperature, hair loss, or color. The pelvic region has a very different anatomy, particularly as is pertains to the sympathetic nervous system and surrounding vasculature. As such, one cannot expect CPP symptoms to present in the same manner as an extremity and Budapest criteria, therefore, should be exempt. Clinicians should be drawing upon physiologic similarities where the pelvic region is responding in a parallel fashion.

There are many parallels between the characterizations and symptoms of chronic pelvic pain (CPP) and complex regional pain syndrome (CRPS), as well as the response to treatment. (Source: Unsplash-Anthony Rao)

Allodynia and Spreading Pain

As stated, patients with CPP often present with allodynia. In patients with CRPS of an extremity, allodynia may present as a feeling of pain to what otherwise would be an innocuous stimulus, such as gently touching the skin or dipping the limb into lukewarm water. In cases of CPP, the stimuli encountered are different but still adhere to the fundamental definition of “allodynia.” Examples of such stimuli that should not be painful include urination, defecation, intercourse, sitting, and wearing undergarments. Patients with CPP typically report pain and discomfort with these otherwise common occurrences.

In cases of CRPS, allodynia is often thought to be due to both peripheral sensitization and central sensitization resulting from an insult or lesion to the peripheral nervous system.1,3 Many patients with CPP report an incident of trauma or surgery, infection, or a painful experience that occurred immediately prior to their development of chronic pain. This stimulus, thought to cause nerve injury, may lead to spontaneous and hyperexcitable primary afferent nociceptors, just as in cases of CRPS. With time, peripheral sensitization of afferent C fibers may trigger central sensitization, which can manifest via symptoms of allodynia and hyperalgesia, just as seen in CRPS.

Further, CPRS has been known to “spread” and involve other organ systems whereby an entire limb may end up affected, rather than just the area initially injured. In cases of CPP, there is significant evidence that symptom involvement is not limited to the initial end organ; painful symptoms may occur in nearby organs as well.4

Changes in Blood Flow

One of the “hallmark” signs of CRPS is color and temperature change, whereby the affected limb swells and becomes blue and cold or red and erythematous. This shift is thought to be due, at least in part, to changes in local blood flow. In the case of CRPS Type 2, trauma to a nerve typically leads to an inflammatory response and neurogenic inflammation. This response brings a host of cells to the injured location consistent with signs often present in acute CRPS. Neurogenic inflammation also occurs, as nociceptors are activated, and may cause antidromic excitation and neurotransmitter release of calcitonin gene-related peptide and substance P from peripheral nerve terminals leading to further inflammation.3 For obvious reasons, pelvic inflammation is not as readily visible as say, an ankle or hand; however, the changes in blood flow do occur, manifesting in a different form.

A large percentage of patients with CPP are found to have pelvic congestion syndrome (PCS), which is an increase of blood flow to the pelvic region.5 Pelvic congestion is a phenomenon thought to be due to incompetent valves in the venous supply to the pelvic region, resulting in venous insufficiency and “congestion."6 This impairment of valves leads to increased venous pressure as well as cell injury with leukocyte infiltration and a number of other inflammatory neurotransmittors (ie, adenosine triphosphate, endothelin, vasopressin, and nitric oxide). Perhaps the finding of PCS in patients with CPP is nothing more than the regional manifestation of the changes in blood flow one would observe in a case of conplex regional pain syndrome.

Response to Blocks

One common theory involving CRPS is a reflexive hyperactivity of the sympathetic nervous system. Consequently, sympathetic nerve blocks have been a popular interventional treatment modality for these patients. While not always effective, in the authors’ experience, patients with CRPS most often report at least a transient improvement in temperature, color, and allodynia with these interventions. In the case of upper extremity CRPS, clinicians typically target the stellate ganglion whereas lower extremity CRPS calls for a block of the lumbar sympathetic chain, most often at the L2 level.

Sympathetic blocks work by preventing the release of noradrenaline from sympathetic fibers located proximal to or in the area of pain, which is thought to disrupt a feedback circuit that can lead to hyperexcitability.3 CPP interventional treatment approaches are very similar – only the targets differ. In patients presenting with CPP, the targets may include the ganglion impar or superior hypogastric plexus. A blockade of the superior hypogastric plexus has been found to affect pain in the lower abdomen and visceral pelvic region, whereas the ganglion of impar may be used to target the perineum, distal rectum, distal urethra, distal vagina, and/or coccygodynia.7

Response to Neuromodulation

Spinal Cord Stimulation (SCS)

In addition to nerve blocks, spinal cord stimulation (SCS) has been a popular treatment modality for patients with chronic neuropathic pain syndromes, such as CRPS, who fail to respond to conservative or less invasive interventional approaches. Given the recalcitrant nature of CPP, as well as basic science showing involvement of the dorsal columns in transmission of pelvic pain, interventional pain physicians have considered that SCS may have a similar benefit on this cohort of patients as well.

Unfortunately, the results have been extremely discouraging, with CPP having the highest rate of explant of any indication for which SCS has been utilized.8 While traditional dorsal column SCS (DC-SCS) has faired better in treating patients with CRPS than in those with CPP based on explant rates, it has not been without its share of failures and largely for the same reasons.9 A major issue that has plagued DC-SCS when it comes to CRPS pain management has been loss of efficacy. Evidence has shown that, after five years, patients with CRPS being treated with DC-SCS and physical therapy (PT) faired no better than those treated with PT alone.10 CRPS most commonly occurs in the lower extremity, more specifically, the foot.9 Much like the pelvic region, this part of the body has proven to be difficult to capture with DC-SCS.9 Consequently, two of the most common complaints accompanying reports of failure of DC-SCS in CRPS is the inability to capture the affected area and unwanted paresthesias in unaffected areas.

Dorsal Root Ganglion (DRG) Stimulation

Over the past 5 to 7 years, shortcomings of DC-SCS in the interventional pain management community have largely served as a driving force behind the development of dorsal root ganglion (DRG) stimulation. Neuromodulators needed to be able to target specific body parts and not have the nuisance of paresthesia overflow. DRG stimulation has since proved to be superior to DC-SCS for the treatment of CRPS with respect to efficacy and its ability to rectify the shortcomings of the therapy.11 We believe that if DRG stimulation could provide the solution for patients with CRPS, it may be able to do the same for those with chronic pelvic pain. In 2019, a small case series was reported by Hunter and Yang using DRG stimulation to treat patients with CPP by placing leads at the L1 and S2 level.12 The authors reported greater than 80% reduction in pain out to 12 months. Similar to CRPS, DRG stimulation provided, in these cases, consistent, targeted stimulation to only the area(s) of need without the downside of paresthesia in other unaffected areas of the body.


Both CRPS and CPP are devastating conditions for men and women alike. For decades, those with CRPS were left to suffer agony, largely due to the medical community’s lack of understanding of the condition and inability to recognize it as a legitimate pathology. In recent years, CRPS has gained widespread recognition and may be identified with greater ease. Unfortunately, since CPP is something that cannot be seen with the naked eye or diagnosed during a physical exam, those afflicted may not be afforded the same benefits as those with CRPS in terms of being identified as a pain syndrome that requires the attention of a pain specialist. Patients with CPP may endure their pain for years before finally finding their way to a pain doctor, often being wrongly treated for a urinary tract infection with countless rounds of antibiotics. Worse still is the failure of many pain doctors to pick up on the similarities that exist between CPP and CRPS and to subsequently treat them with the same level of respect and diligence. It may only be in the hands of a pain doctor who specializes in pelvic pain that these patients ultimately find appropriate treatment.

Last updated on: October 7, 2019
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