Segmental hyperalgesia to mechanical stimulus in interstitial cystitis/bladder pain syndrome: evidence of central sensitization

Pathomechanism of Interstitial Cystitis/Bladder Pain Syndrome and Mapping the Heterogeneity of Disease

Interstitial cystitis/bladder pain syndrome (IC/BPS) is a heterogeneous syndrome which is usually characterized by urinary frequency, nocturia, and bladder pain. Several pathomechanisms have been proposed, including uroepithelial dysfunction, mast cell activation, neurogenic inflammation, autoimmunity, and occult urinary tract infections. It is possible that an inflammatory process alters regulation of urothelial homeostasis and results in dysfunction of the bladder epithelium. Different phenotypes of IC/BPS have been explored including Hunner and non-Hunner type IC, hypersensitive bladder, and bladder pain both with and without functional somatic syndrome. Different gene expressions have also been found in different IC phenotypes. Abnormal expressions of uroplakin, chondroitin sulfate and adhesive protein E-cadherin, tight junction protein zonula occludens-1 in IC/BPS bladder suggest abnormal epithelial differentiation in this bladder disease. Analysis of inflammatory proteins, or cytokines in the urine or serum provides another diagnostic foundation forIC/BPS subtypes. The involvement of IC/BPS in systemic functional somatic syndrome and other pelvic organ diseases might also subdivide subtypes of IC/BPS. Chronic inflammation, increased urothelial apoptosis, and abnormal urothelial function are closely associated in IC bladders. This article reviews recent research on the pathomechanisms of IC, which might help us in mapping the heterogeneity of the disease.

Heightened cold pain and pressure pain sensitivity in young female adults with moderate-to-severe menstrual pain

This study investigated the association between menstrual pain severity and psychophysical measures of cold and pressure pain sensitivity. A cross-sectional design was used with young women (n = 432) from the Western Australian Pregnancy Cohort (Raine) Study. Menstrual pain severity and oral contraception use was obtained from questionnaires at 20 and 22-year follow-ups. A visual analog scale (VAS; range from 0 [none] to 10 [unbearable]) was used to measure menstrual pain severity at both 20 and 22 years over the 3-year period, with 3 groups created: (1) no pain or mild pain (VAS 0-3), (2) at least moderate pain at a minimum of 1 of the 2 time points (hereafter named "mixed)", and (3) severe pain (VAS 8-10). Cold pain sensitivity (dorsal wrist) and pressure pain sensitivity (lumbar spine, upper trapezius, dorsal wrist, and tibialis anterior) were assessed using standardised quantitative sensory testing protocols. Confounding variables included number of musculoskeletal pain sites, oral contraceptive use, smoking, physical activity, body mass index, psychological distress, and sleep. Severe menstrual pain and mixed menstrual pain were positively associated with heightened cold pain sensitivity (distant from menstrual pain referral site) and pressure pain sensitivity (local to menstrual pain referral site). These associations remained significant after adjusting for potential confounding variables including multisite musculoskeletal pain. Our findings suggest peripheral and central neurophysiological mechanisms contributing to heightened pain sensitivity in young women with moderate and severe menstrual pain. These data highlight the need for innovative management approaches to attenuate the negative impact of severe menstrual pain in young women.

Does central sensitization help explain idiopathic overactive bladder?

The pathophysiological mechanisms underlying overactive bladder syndrome (OAB) can include dysfunction of sensory pathways of the peripheral and central nervous systems, resulting in bladder hypersensitivity. Central sensitization describes an induced state of spinal hypersensitivity that is associated with a variety of chronic pain disorders that share many attributes with OAB, albeit without the presence of pain. As such, the concept of central sensitization might be relevant to understanding the mechanisms and clinical manifestations of OAB syndrome. An understanding of the pathophysiology and clinical manifestations of central sensitization, and the evidence that supports a role of central sensitization in OAB, including the potential implications of mechanisms of central sensitization for the treatment of patients with OAB could provide a novel approach to the treatment of patients with this disease. Such an approach would be especially relevant to those patients with central sensitization-related comorbidities, and has the potential to improve the outcomes of these patients in particular.

Painful Reality: Inappropriate Provider Management of Pain as a Determinant of Health Care Avoidance

Although pain is often characterized as a subjective, highly individualized phenomenon, in fact, numerous elements which are simply biological in nature underlie interpersonal differences in pain experience that influence the effectiveness of provider pain management. Elements acting at the level of tissues and cells include signal-transmitting molecules in pain pathways; elements acting at the level of the whole person comprise entire brain networks and anatomic elements fostering pain vulnerability. However, knowledge of these elements and translation of such knowledge into practical means for relieving patient pain is dismayingly sparse across the total spectrum of health care professionals. A serious consequence of this knowledge and action gap is that isolated, or worse yet, repeated, pain experiences may lead to profound mistrust of the health care system and its providers and to health care avoidance (e.g., mammography). This article outlines a biologic knowledge base and proposed remedies to improve pain management across the entire domain of health care. Key components of this approach include enhanced education for providers and informational outreach to health care consumers, clarifying pain mechanisms to both constituencies. Moreover, increased accountability within the health care system is needed, both in knowing and applying well-established biomedical knowledge and in best using technical and interpersonal skills necessary for effective pain management.

Clinical guidelines for interstitial cystitis and hypersensitive bladder updated in 2015

Clinical guidelines for interstitial cystitis and hypersensitive bladder have been updated as of 2015. The guidelines define interstitial cystitis by the presence of hypersensitive bladder symptoms (discomfort, pressure or pain in the bladder usually associated with urinary frequency and nocturia) and bladder pathology, after excluding other diseases explaining symptoms. Interstitial cystitis is further classified by bladder pathology; either Hunner type interstitial cystitis with Hunner lesions or non-Hunner type interstitial cystitis with mucosal bleeding after distension in the absence of Hunner lesions. Hypersensitive bladder refers to a condition, where hypersensitive bladder symptoms are present, but bladder pathology or other explainable diseases are unproven. Interstitial cystitis and hypersensitive bladder severely affect patients' quality of life as a result of disabling symptoms and/or comorbidities. Reported prevalence suggestive of these disorders varies greatly from 0.01% to >6%. Pathophysiology would be an interaction of multiple factors including urothelial dysfunction, inflammation, neural hyperactivity, exogenous substances and extrabladder disorders. Definite diagnosis of interstitial cystitis and hypersensitive bladder requires cystoscopy with or without hydrodistension. Most of the therapeutic options lack a high level of evidence, leaving a few as recommended therapeutic options.

Pelvic floor dysfunction and sensory impairment: Current evidence

AIMS

To explore the role of sensory nerve impairment in women with pelvic organ prolapse, painful bladder syndrome, urinary and fecal incontinence, and sexual dysfunction.

METHODS

Medline and Embase were searched for articles in which sensory testing, either quantitative sensory testing or current perception thresholds, had been used to evaluate women with pelvic organ prolapse, stress and urge urinary incontinence, fecal incontinence and female sexual dysfunction. All search terms were expanded within each database prior to searching.

RESULTS

Research to date has included small numbers of participants, used poorly matched controls, lacked a systemic sensory examination and applied non-standardized sensory testing techniques. However, the evidence suggests women with pelvic organ prolapse demonstrate sensory dysfunction. The role of sensory impairment in stress urinary incontinence is inconclusive. In women with urge urinary incontinence there is some evidence to suggest it may be urethrally mediated. Women with painful bladder syndrome may have more sensitive nerve endings which are unable to ignore repeated stimuli. Sensory impairment is common in women with sexual dysfunction, typically involving larger nerve fibres. There were no studies evaluating sensory function in women with fecal incontinence.

CONCLUSION

Current evidence suggests women with pelvic floor dysfunction demonstrate sensory impairment though the causes remain unclear. Further studies are needed to investigate the different conditions of pelvic floor dysfunction using standardized sensory testing techniques, as well as evaluate the timing and mechanism by which any sensory impairment develops. Neurourol. Urodynam. 36:550-556, 2017. © 2016 Wiley Periodicals, Inc.

Alterations in Connectivity on Functional Magnetic Resonance Imaging with Provocation of Lower Urinary Tract Symptoms: A MAPP Research Network Feasibility Study of Urological Chronic Pelvic Pain Syndromes

PURPOSE

Urological chronic pelvic pain syndromes have refractory bladder or pelvic pain as the dominant symptom. This has been attributed to changes in the central nervous system caused by a chronic barrage of noxious stimuli. We developed what is to our knowledge a novel challenge protocol that induced bladder distention in study participants to reproduce pain and urinary symptoms. We tested to see whether it could discriminate between persons with urological chronic pelvic pain syndrome-like symptoms and asymptomatic controls.

MATERIALS AND METHODS

We recruited 10 female twin pairs who were discordant for urological chronic pelvic pain syndrome-like symptoms. Before scanning each twin urinated to completion and then consumed 500 cc water. Each twin was scanned with our resting state functional magnetic resonance imaging protocol immediately and approximately 50 minutes after consumption. Time series were extracted from the right and left periaqueductal gray, and the right and left amygdala subregions. We performed the repeated measures 2-sample t-test to assess differences in connectivity between symptomatic and asymptomatic twins before and after bladder distention.

RESULTS

Group by condition interaction effects were found from the periaqueductal gray to the right cerebellum VIIIa, the amygdala, the right premotor cortex/supplementary motor area and the insular cortex, and between the amygdala and the frontal pole/medial orbital frontal cortex, the hypothalamus, the insular cortex, the thalamus and the anterior cingulate cortex.

CONCLUSIONS

These findings demonstrate that our noninvasive bladder distention protocol can detect differences in the processing of urinary sensation between twins discordant for lower urinary tract pain.

Multimodal nociceptive mechanisms underlying chronic pelvic pain

OBJECTIVE

We sought to evaluate candidate mechanisms underlying the pelvic floor dysfunction in women with chronic pelvic pain (CPP) and/or painful bladder syndrome (PBS)/interstitial cystitis. Notably, prior studies have not consistently controlled for potential confounding by psychological or anatomical factors.

STUDY DESIGN

As part of a larger study on pelvic floor pain dysfunction and bladder pain sensitivity, we compared a measure of mechanical pain sensitivity, pressure pain thresholds (PPTs), between women with pelvic pain and pain-free controls. We also assessed a novel pain measure using degree and duration of postexam pain aftersensation, and conducted structural and functional assessments of the pelvic floor to account for any potential confounding. Phenotypic specificity of pelvic floor measures was assessed with receiver operator characteristic curves adjusted for prevalence.

RESULTS

A total of 23 women with CPP, 23 women with PBS, and 42 pain-free controls completed the study. Women with CPP or PBS exhibited enhanced pain sensitivity with lower PPTs (1.18 [interquartile range, 0.87-1.41] kg/cm(2)) than pain-free participants (1.48 [1.11-1.76] kg/cm(2); P < .001) and prolonged pain aftersensation (3.5 [0-9] vs 0 [0-1] minutes; P < .001). Although genital hiatus (P < .01) was wider in women with CPP there were no consistently observed group differences in pelvic floor anatomy, muscle tone, or strength. The combination of PPTs and aftersensation duration correlated with severity of pelvic floor tenderness (R(2), 41-51; P < .01). Even after adjustment for prevalence, the combined metrics discriminated pain-free controls from women with CPP or PBS (area under the curve, 0.87).

CONCLUSION

Both experimental assessment of pelvic floor pain thresholds and measurement of sustained pain are independently associated with pelvic pain phenotypes. These findings suggest systematic clinical assessment of the time course of provoked pain symptoms, which occurs over seconds for mechanical pain thresholds vs minutes for aftersensation pain, would be helpful in identifying the fundamental mechanisms of pelvic floor pain. Longitudinal studies of therapies differentially targeting these discrete mechanisms are needed to confirm their clinical significance.

Animal Models of Urologic Chronic Pelvic Pain Syndromes: Findings From the Multidisciplinary Approach to the Study of Chronic Pelvic Pain Research Network

OBJECTIVE

To describe the approach taken by the Multidisciplinary Approach to the Study of Chronic Pelvic Pain Research Network investigators to advance the utility of urologic chronic pelvic pain syndromes (UCPPS) animal models.

METHODS

A multidisciplinary team of investigators representing basic science and clinical expertise defined key phenotypic criteria for rodent models of UCPPS. UCPPS symptoms were prioritized based on their clinical significance. Methods for quantifying animal correlates to patient symptoms were developed. The methods were implemented across proposed rodent models for evaluation and comparison of animals for phenotypic characteristics relevant to human symptomatology.

RESULTS

Pelvic pain and urinary frequency were deemed primary features of human UCPPS and were prioritized for assessment in animals. Nociception was quantified using visceromotor response to bladder distention and by applying von Frey filaments to the lower abdomen (referred tactile allodynia). Micturition activity was assessed as free voiding using micturition cages or blotting pad assays and in response to bladder filling by cystometry. Models varied in both depth of characterization and degree of recapitulating pelvic pain and urinary frequency characteristics of UCPPS.

CONCLUSION

Rodent models that reflect multiple key characteristics of human UCPPS may be identified and provide enhanced clinical significance to mechanistic studies. We have developed a strategy for evaluating current and future animal models of UCPPS based on human symptomatology. This approach provides a foundation for improved translation between mechanistic studies in animals and clinical research and serves as a validation strategy for assessing validity of models for symptom-driven disorders of unknown etiology.

The MAPP research network: design, patient characterization and operations

Background

The “Multidisciplinary Approach to the Study of Chronic Pelvic Pain” (MAPP) Research Network was established by the NIDDK to better understand the pathophysiology of urologic chronic pelvic pain syndromes (UCPPS), to inform future clinical trials and improve clinical care. The evolution, organization, and scientific scope of the MAPP Research Network, and the unique approach of the network’s central study and common data elements are described.

Methods

The primary scientific protocol for the Trans-MAPP Epidemiology/Phenotyping (EP) Study comprises a multi-site, longitudinal observational study, including bi-weekly internet-based symptom assessments, following a comprehensive in-clinic deep-phenotyping array of urological symptoms, non-urological symptoms and psychosocial factors to evaluate men and women with UCPPS. Healthy controls, matched on sex and age, as well as “positive” controls meeting the non-urologic associated syndromes (NUAS) criteria for one or more of the target conditions of Fibromyalgia (FM), Chronic Fatigue Syndrome (CFS) or Irritable Bowel Syndrome (IBS), were also evaluated. Additional, complementary studies addressing diverse hypotheses are integrated into the Trans-MAPP EP Study to provide a systemic characterization of study participants, including biomarker discovery studies of infectious agents, quantitative sensory testing, and structural and resting state neuroimaging and functional neurobiology studies. A highly novel effort to develop and assess clinically relevant animal models of UCPPS was also undertaken to allow improved translation between clinical and mechanistic studies. Recruitment into the central study occurred at six Discovery Sites in the United States, resulting in a total of 1,039 enrolled participants, exceeding the original targets. The biospecimen collection rate at baseline visits reached nearly 100%, and 279 participants underwent common neuroimaging through a standardized protocol. An extended follow-up study for 161 of the UCPPS participants is ongoing.

Discussion

The MAPP Research Network represents a novel, comprehensive approach to the study of UCPPS, as well as other concomitant NUAS. Findings are expected to provide significant advances in understanding UCPPS pathophysiology that will ultimately inform future clinical trials and lead to improvements in patient care. Furthermore, the structure and methodologies developed by the MAPP Network provide the foundation upon which future studies of other urologic or non-urologic disorders can be based.

Trial registration

ClinicalTrials.gov identifier: NCT01098279 “Chronic Pelvic Pain Study of Individuals with Diagnoses or Symptoms of Interstitial Cystitis and/or Chronic Prostatitis (MAPP-EP)”. http://clinicaltrials.gov/show/NCT01098279