Identification and treatment of new inflammatory triggers for complex regional pain syndrome: small intestinal bacterial overgrowth and obstructive sleep apnea
Weinstock LB, Myers TL, Walters, AS, Schwartz, OA, Younger JW, Chopra PJ, Guarino AH.
Complex regional pain syndrome (CRPS) is evoked by conditions which may be associated with local and/or systemic inflammation. We present a case report of long-standing CRPS in an Ehlers-Danlos patient where prolonged remission was attained by directing therapy towards concomitant small intestinal bacterial overgrowth (SIBO), obstructive sleep apnea (OSA), and potential increased microglia activity. We theorize that cytokine production produced by SIBO and OSA may act as stimuli for ongoing CRPS symptoms. CRPS may also benefit from the properties of low dose naltrexone (LDN) which blocks microglia Toll-like receptors and induces production of endorphins which regulate and reduce inflammation.
Complex regional pain syndrome (CRPS), formally known as reflex sympathetic dystrophy, is a neuropathic pain disorder that may fail to respond to current therapy including a variety of medications, nerve blocks, and ketamine infusions (1, 2). The incidence of CRPS is uncertain as there are few epidemiological studies. In the Mayo Clinic study, the rate was 5.46 per 100,000 person years in comparison to a 6-fold larger study in the Netherlands where the rate was 26.2 per 100,000 person years (3, 4). A marked female predominance was noted in each study. A familial occurrence of CRPS has been described (5). The natural history of CRPS varies widely. The Mayo Clinic reported that 56 of the 74 patients with CRPS for 1 month - 5 years had complete remission after various treatments. Spontaneous remission was observed when the initial symptoms were mild (3). By way of comparison, there were no remissions in 656 Drexel University patients who had CRPS for 1 - 46 years (6). Pain had only modest improvement with their treatments. No spontaneous remissions occurred in 102 Dutch database patients who had CRPS for 2.1 - 10.8 years (7). Progressive disease was reported in 16% and permanent disability was present in 31% of the Dutch patients.
Pathophysiological consequences of cytokine release, microglia activation, central sensitization, and autonomic nervous system dysfunction result in regional pain along with vasomotor, motor/trophic, and sudomotor/edema dysfunction (1, 2, 8, 9). Microglia cells are an integral part of the anatomic framework of the nervous system with attachments to astrocytes (10). They act as neuromodulators which alter central nervous cell and spinal sensory neuron excitability. Various syndromes marked by hyperalgesia including fibromyalgia and CRPS may be mediated by microglia cell activation as a consequence of pro-inflammatory cytokines (11, 12). Events known to evoke CRPS include bone fractures, sprains, trauma (injections, nerve injury, surgery, burns, and frostbite), nerve injury, infection, stroke, myocardial infarction, and pregnancy (1, 2). Many of these triggers may be associated with local and/or systemic inflammation (13 - 16). Therefore it is theoretically possible that cytokine release by these disorders could act as mediators for CRPS via activation of microglia. Parkitny et al performed a systematic and meta-analysis review of the role of inflammation in acute and chronic CRPS (17). In the former, serum interleukin-8 and tumor necrosis factors are increased. In the latter, there are many inflammatory markers in serum, blister fluid, and the cerebral spinal fluid. All of the Mayo Clinic patients reported an antecedent event, with bone fracture being the most common trigger (46%) (3). Fractures are associated with elevated cytokines and C-reactive protein in animal models (13). Chronic systemic inflammation has been shown to be an independent risk factor for bone fractures in humans (14), thus a fracture that precipitates CRPS may stem from a pre-existing chronic inflammatory state.
Since the pathophysiology of CRPS is not clear and no single therapy is effective, it is desirable to consider all theories. We present a case report of long-standing CRPS in a patient with Ehlers-Danlos where prolonged remission was attained by directing therapy towards concomitant small intestinal bacterial overgrowth (SIBO), obstructive sleep apnea (OSA), and potential increased microglia activity. We theorize that cytokine production produced by SIBO and OSA act as stimuli for ongoing CRPS symptoms. Written consent was obtained from the patient to publish this article.
A 56 year-old Caucasian woman had continuous severe leg pain with episodic pain in the arms and nose since May 2005. Pain first started in the right groin after a cardiac catheterization for evaluation of atypical chest pain. After 5 months, the pain had spread down her leg. Asymmetric, shiny skin with fluctuating temperature changes (up to 10o Fahrenheit), color change, and edema developed. The continuous leg pain worsened 2 years later when she had a spontaneous right ankle fracture. Severe skin blistering occurred beneath the cast. Mild to moderate arm and nose pain subsequently occurred mainly in cold weather. Diagnosis of CRPS was confirmed by four pain management centers. The patient failed sympathetic ganglion blocks and gabapentin. Prolonged use of opioids worsened the pain.
A 45-year history of irritable bowel syndrome was characterized by post-prandial bloating, excessive and foul flatus, and diarrhea. Fatigue, anxiety, and a sleep disorder were present for several years prior to the onset of CRPS. A 2010 sleep laboratory polysomnography evaluation was reviewed. This had been performed to evaluate snoring, daytime hypersomnolence, morning headaches, and awakening with gasping for breath. The Apnea-Hypopnea Index was 15 with a Respiratory Disturbance Index of 58 (documentation of desaturation was not available). In 2010 implementation of nasal mask CPAP at 12 cm H2O was performed. Despite CPAP use, symptoms of sleep apnea continued and intolerance of the device resulted in reduction of CPAP use. Periodic use of alprazolam, bupropion, and nortriptyline increased the depth of sleep and reduced anxiety, but did not improve fatigue and sleep apnea symptoms.
In October 2013 the patient returned for a second evaluation for atypical chest pain and fatigue. Sleep Medicine was asked to consult again. Gastroenterology was consulted for the first time. The blood pressure was 130/80 mm Hg and pulse 80 beats per minute. Body mass index was 29.3 kg/m2. There was diffuse mild abdominal tenderness. Edema, blue discoloration, and tenderness were present in the right leg (Fig. 1). She exhibited joint hypermobility with the Ehlers-Danlos syndrome Beighton joint flexibility score of 8/9. The patient met 3 major criteria and 5 minor Villefranche criteria diagnostic for the hypermobility type of Ehlers-Danlos syndrome (18). This diagnosis was supported by her family history where 3 generations had many features of Ehlers-Danlos syndrome. The C-reactive protein was elevated at 3.9 mg/L (normal range: 1.0-3.0). A hiatus hernia was diagnosed by endoscopy. Small intestinal bacterial overgrowth was diagnosed by a lactulose breath test. A repeat sleep laboratory evaluation was performed and BiPAP titration was completed with optimal settings of 15/11 with nasal mask. Rifaximin was given for SIBO (1650 mg/day/2-weeks) and long-term low dose naltrexone (LDN) (4.5 mg/daily) was prescribed based on success in a prior publication (19).
At the 1-month gastroenterology clinic visit, she reported a marked improvement in her leg and bowel symptoms. LDN was continued long-term. At the 3-month Sleep Medicine clinic visit, interrogation of the sleep apnea device over 90 days revealed 82% use >4 hours with 6 hours average use per night. At a 16-month gastroenterology clinic visit she returned with complaints of 1 month of bloating, fatigue, and episodic minor attacks of pain in the arms and nose in cold weather. Inadequate treatment of sleep apnea was suspected as the patient revealed she would often have nightmares and in the morning she would find her BiPAP device on the floor. There was mild diffuse abdominal tenderness. Complete remission of CRPS was noted in the right leg (Fig. 2). Naltrexone was continued at 4.5 mg/day to maintain CRPS therapy and three therapies were added: 1) rifaximin (1650 mg/day for one month) to retreat SIBO; 2) erythromycin (50 mg/nightly long-term which acts as motilin-like hormone to stimulate the small intestinal migrating motor complex which reduces SIBO relapse) (20); and 3) Clonazepam (1 mg/nightly) to reduce nightmares to reduce the urge to remove the BiPAP device. Multiple communications over the following eight months revealed that there had been rapid and sustained remission of all CRPS pain, bowel symptoms, and fatigue. At the 6-month Sleep Medicine clinic visit,, interrogation of the BiPap device over 30 days documented improved to 100% use >4 hours with >7 hours average use per night.
Figure 1. October 2013: Asymmetric edema and discoloration in the right leg.
Figure 2. December 2014: Signs of CRSP have resolved. The scar from ankle surgery better visualized.
In this case report, remission of CRPS was attained by directing therapy towards SIBO, OSA, and potential increased microglia activity. We theorize that cytokine production including tumor necrosis factor produced by SIBO (20) and OSA (21) may act as stimuli for ongoing CRPS symptoms.
There is a known relationship of CRPS and the gastrointestinal tract. Dysbiosis (alterations of the microbiome) and increased intestinal permeability have been reported in CRPS and these conditions also cause chronic systemic inflammation (22 Ã¢â‚¬â€œ 24). Irritable bowel syndrome is common in CRPS although the relationship has hitherto not been elucidated (25). SIBO may be a pathological factor in up to 50% of irritable bowel syndrome patients and it can cause systemic inflammation and extra-intestinal disorders including fibromyalgia, restless legs syndrome, rosacea, and chronic pelvic pain syndromes (20). Treatment of both SIBO and irritable bowel syndrome with rifaximin, a non-absorbed, gut-directed antibiotic has been extensively studied (26). Experimental therapy of unregulated inflammation and microglia activation using low dose naltrexone (LDN) has been reported in pain disorders including two cases of CRPS (11, 19).
Ehlers-Danlos syndrome is a dominant inherited systemic disorder and the incidence may be as high as 2% of the population (18). This syndrome is commonly missed in childhood and adults may present with a unique set of problems that may leave physicians confounded as seen in our patient and her kindred. Published reports of concomitant CRPS and Ehlers-Danlos are rare (18, 27). The authors of the case series with four patients proposed that Ehlers-Danlos contributed to CRPS via stretch injury to nerves traversing hypermobile joints, increased fragility of nerve connective tissue, and/or nerve trauma from more frequent surgery (27). Subsequently, both syndromes have subsequently have been concurrently diagnosed in approximately 25% of one of the author's pain management practice (PJC).
Alternative mechanisms whereby Ehlers-Danlos syndrome contributes to CRPS are proposed. Ehlers-Danlos syndrome causes OSA owing to connective tissue laxity (28) and thus subsequent chronic hypoxia-induced inflammation (21) may contribute to CRPS activation. This mechanism appeared to play a role in our patient since complete remission of all CRPS symptoms was not attained until sleep apnea therapy was optimized. In addition, inflammation from SIBO (20) may contribute to CPRS activation. Gastrointestinal symptoms are common in both Ehlers-Danlos syndrome and in CRPS (29, 25). In Ehlers-Danlos syndrome, SIBO and small intestinal motility changes have been reported: dilated small intestinal diameter, small bowel diverticulosis, small intestinal motility disorders, and loose connective tissue in the mesentery that allows for drooping of the small intestine to create a relative blind loop (30 - 33). Defective collagen synthesis, ÃÅ½Â±-actin deficiency, and autonomic dysfunction are potential explanations for abnormal motility (34, 35). SIBO may be common in CRPS since Goebel et al demonstrated that increased intestinal permeability was common in CRPS (23). A recent case report using long-term cephalosporin to keep CRPS in remission supports the idea that manipulation of the microbiome may play a role in CRPS therapy (36). Finally, the severity of CRPS may be enhanced in Ehlers-Danlos syndrome patients owing to central hypersensitivity (37).
In the case study herein, low dose naltrexone (LDN) was administered to attenuate microglia activation via blocking Toll-like receptors 2 and 4 (11, 19). In addition, LDN causes rebound met-enkephelin production which then regulates systemic inflammation by regulating T- and B-cell lymphocyte response and cytokine production which is important in CRPS (11, 17). This is now the third reported case where LDN has demonstrated improvement in CRPS symptoms (19). Subsequently, one of the authors (PJC) has employed this therapy frequently in his practice and has observed therapeutic benefit in CRPS patients. Administration of LDN as off-label use for pain control is experimental.
Limitations of this study include that CRPS symptoms might have gone into spontaneous remission although most patients suffer for many years (6, 7). The unremitting nature of this patient's symptoms and the rapid response to each course of therapy argue against this concern. Multimodality therapy was administered so it is unknown how much each contributed to remission of CRPS symptoms. Nonetheless, a multimodality approach by pain management physicians is commonplace (1).
Physicians may not be familiar with the SIBO link to irritable bowel syndrome and may be dismissed as an unrelated syndrome. OSA may go unrecognized since sleep disturbance is common in CRPS and is often blamed on pain. An epidemiological study of the prevalence of Ehlers-Danlos, SIBO, and OSA is required to further understand the roles that these conditions may play in CRPS. It is possible that undiagnosed Ehlers-Danlos syndrome in CRPS patients could also explain some cases of familial CRPS. We theorize that recognition and treatment of underlying causes of inflammation is likely to be an important future modality in CRPS.
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