Multimodal Vulvar and Peripheral Sensitivity Among Women With Vulvodynia: A Case-Control Study

Deciphering nociplastic pain: clinical features, risk factors and potential mechanisms

Nociplastic pain is a mechanistic term used to describe pain that arises or is sustained by altered nociception, despite the absence of tissue damage. Although nociplastic pain has distinct pathophysiology from nociceptive and neuropathic pain, these pain mechanisms often coincide within individuals, which contributes to the intractability of chronic pain. Key symptoms of nociplastic pain include pain in multiple body regions, fatigue, sleep disturbances, cognitive dysfunction, depression and anxiety. Individuals with nociplastic pain are often diffusely tender - indicative of hyperalgesia and/or allodynia - and are often more sensitive than others to non-painful sensory stimuli such as lights, odours and noises. This Review summarizes the risk factors, clinical presentation and treatment of nociplastic pain, and describes how alterations in brain function and structure, immune processing and peripheral factors might contribute to the nociplastic pain phenotype. This article concludes with a discussion of two proposed subtypes of nociplastic pain that reflect distinct neurobiological features and treatment responsivity.

Distinct neural signaling characteristics between fibromyalgia and provoked vestibulodynia revealed by means of functional magnetic resonance imaging in the brainstem and spinal cord

Introduction

Fibromyalgia and provoked vestibulodynia are two chronic pain conditions that disproportionately affect women. The mechanisms underlying the pain in these conditions are still poorly understood, but there is speculation that both may be linked to altered central sensitization and autonomic regulation. Neuroimaging studies of these conditions focusing on the brainstem and spinal cord to explore changes in pain regulation and autonomic regulation are emerging, but none to date have directly compared pain and autonomic regulation in these conditions. This study compares groups of women with fibromyalgia and provoked vestibulodynia to healthy controls using a threat/safety paradigm with a predictable noxious heat stimulus.

Methods

Functional magnetic resonance imaging data were acquired at 3 tesla in the cervical spinal cord and brainstem with previously established methods. Imaging data were analyzed with structural equation modeling and ANCOVA methods during: a period of noxious stimulation, and a period before the stimulation when participants were expecting the upcoming pain.

Results

The results demonstrate several similarities and differences between brainstem/spinal cord connectivity related to autonomic and pain regulatory networks across the three groups in both time periods.

Discussion

Based on the regions and connections involved in the differences, the altered pain processing in fibromyalgia appears to be related to changes in how autonomic and pain regulation networks are integrated, whereas altered pain processing in provoked vestibulodynia is linked in part to changes in arousal or salience networks as well as changes in affective components of pain regulation.

Mechanistic and thermal characterization of acupuncture for chemotherapy-induced peripheral neuropathy as measured by quantitative sensory testing

PURPOSE

Chemotherapy-induced peripheral neuropathy (CIPN) is a common and debilitating side effect of chemotherapy. Acupuncture is a promising non-pharmacological intervention for CIPN. However, the physiological effects of acupuncture treatment remain poorly understood. We examined the effects of acupuncture on CIPN using semi-objective quantitative sensory testing (QST).

METHODS

We conducted a randomized controlled trial of real acupuncture (RA) and sham acupuncture (SA) compared to usual care (UC) in cancer survivors with moderate-to-severe CIPN. Treatment response was assessed with QST measures of tactile and vibration detection thresholds in hands and feet, thermal detection, and pain thresholds at weeks 0, 8, and 12. Constrained linear mixed model (cLMM) regression was used for statistical analysis.

RESULTS

63 patients completed QST testing. At week 8, vibrational detection thresholds in feet were significantly lower in RA and SA (p = 0.019 and p = 0.046) than in UC, with no difference between RA and SA (p = 0.637). Both RA and SA also showed significantly higher cool thermal detection than UC (p = 0.008 and p = 0.013, respectively), with no difference between RA and SA (p = 0.790). No differences in tactile detection, vibrational detection in hands, warm thermal detection, and thermal pain thresholds were detected among the three arms at weeks 8 and 12.

CONCLUSION

QST demonstrated different patterns in RA, SA, and UC. After eight weeks of RA, we observed significant improvements in the vibrational detection threshold in feet and cool thermal detection threshold in hands compared to UC. No significant differences were seen when compared to SA.

TRIAL REGISTRATION

ClinicalTrials.gov (NCT03183037); June 9, 2017.

Evaluation and Treatment of Vulvodynia: State of the Science

Vulvodynia affects 7% of American women, yet clinicians often lack awareness of its presentation. It is underdiagnosed and often misdiagnosed as vaginitis. The etiology of vulvodynia remains unknown, making it difficult to identify or develop effective treatment methods. The purpose of this article is to (1) review the presentation and evaluation of vulvodynia, (2) review the research on vulvodynia treatments, and (3) aid the clinician in the selection of vulvodynia treatment methods. The level of evidence to support vulvodynia treatment varies from case series to randomized controlled trials (RCTs). Oral desipramine with 5% lidocaine cream, intravaginal diazepam tablets with intravaginal transcutaneous electric nerve stimulation (TENS), botulinum toxin type A 50 units, enoxaparin sodium subcutaneous injections, intravaginal TENS (as a single therapy), multimodal physical therapy, overnight 5% lidocaine ointment, and acupuncture had the highest level of evidence with at least one RCT or comparative effectiveness trial. Pre to posttest reduction in vulvar pain and/or dyspareunia in non-RCT studies included studies of gabapentin cream, amitriptyline cream, amitriptyline with baclofen cream, up to 6 weeks' oral itraconazole therapy, multimodal physical therapy, vaginal dilators, electromyography biofeedback, hypnotherapy, cognitive behavioral therapy, cold knife vestibulectomy, and laser therapy. There is a lack of rigorous RCTs with large sample sizes for the treatment of vulvodynia, rendering it difficult to determine efficacy of most treatment methods. Clinicians will be guided in the selection of best treatments for vulvodynia that have the highest level of evidence and are least invasive.

Experimental Pain and Auditory Sensitivity in Overactive Bladder Syndrome: A Symptoms of the Lower Urinary Tract Dysfunction Research Network (LURN) Study

PURPOSE

The objective of this study was to investigate the presence of nonbladder sensory abnormalities in participants with overactive bladder syndrome (OAB).

MATERIALS AND METHODS

Symptoms of Lower Urinary Tract Dysfunction Research Network (LURN) study participants with OAB symptoms and controls were recruited from 6 U.S. tertiary referral centers. Quantitative sensory testing (QST) was performed to determine pressure pain sensitivity at the thumbnail bed and auditory sensitivity. Fixed and mixed effect multivariable linear regressions and Weibull models were used to compare QST responses between groups. Pearson correlations were used to assess the relationship between QST measures. Associations between QST and self-reported symptoms were explored with linear regression.

RESULTS

A total of 297 participants were analyzed (191 OAB, 106 controls; 76% white, 51% male). OAB cases were older than controls (57.4 vs 52.2 years, p=0.015). No significant differences in experimental thumbnail (nonbladder) pain or auditory sensitivity were detected between OAB cases and controls. Correlations between pressure and auditory derived metrics were weak to moderate overall for both groups, with some significantly stronger correlations for cases. Exploratory analyses indicated increased pressure pain and auditory sensitivity were modestly associated with greater self-reported bladder pain and pain interference with physical function.

CONCLUSIONS

As a group, no significant differences between OAB cases and controls were observed in experimental nonbladder pain or auditory sensitivity during QST. Associations between QST outcomes and clinical pain raise the possibility of centrally mediated sensory amplification in some individuals with OAB.

Vulvodynia

Vulvodynia is a heterogenous, chronic pain condition of unknown etiology that affects 7% to 15% of women. It affects sexual function and quality of life. Vulvodynia can be primary or secondary, localized or generalized, and spontaneous or provoked. Contributing factors for provoked vulvodynia might include vulvovaginal infections, low estrogen states, and underlying anxiety disorder. Generalized vulvodynia likely arises from underlying connective tissue or neurological dysfunction. Vulvodynia treatment must be individualized on the basis of the patient's presentation and physical examination findings. Surgical excision of the vulvar vestibule has high success rates but other modalities showing success include pelvic floor physical therapy and cognitive-behavioral therapy.

Quantitative assessment of nonpelvic pressure pain sensitivity in urologic chronic pelvic pain syndrome: a MAPP Research Network study

Experimental pain sensitivity was assessed in individuals with urologic chronic pelvic pain syndrome (UCPPS) as part of the Multidisciplinary Approach to the Study of Chronic Pelvic Pain (MAPP) Research Network. A series of computer-controlled pressure stimuli were delivered to the thumbnail bed, an asymptomatic site distant from the area of UCPPS pain that is considered to be indicative of overall body pain threshold. Stimuli were rated according to a standardized magnitude estimation protocol. Pain sensitivity in participants with UCPPS was compared with healthy controls and a mixed pain group composed of individuals with other chronic overlapping pain conditions, including fibromyalgia, chronic fatigue, and irritable bowel syndromes. Data from 6 participating MAPP testing sites were pooled for analysis. Participants with UCPPS (n = 153) exhibited an intermediate pain sensitivity phenotype: they were less sensitive relative to the mixed pain group (n = 35) but significantly more sensitive than healthy controls (n = 100). Increased pain sensitivity in patients with UCPPS was associated with both higher levels of clinical pain severity and more painful body areas outside the pelvic region. Exploratory analyses in participants with UCPPS revealed that pain sensitivity increased during periods of urologic symptom flare and that less pressure pain sensitivity at baseline was associated with a greater likelihood of subsequent genitourinary pain improvement 1 year later. The finding that individuals with UCPPS demonstrate nonpelvic pain hypersensitivity that is related to clinical symptoms suggests that central nervous system mechanisms of pain amplification contribute to UCPPS.

Deep Dyspareunia: Review of Pathophysiology and Proposed Future Research Priorities

INTRODUCTION

Dyspareunia has been traditionally divided into superficial (introital) dyspareunia and deep dyspareunia (pain with deep penetration). While deep dyspareunia can coexist with a variety of conditions, recent work in endometriosis has demonstrated that coexistence does not necessarily imply causation. Therefore, a reconsideration of the literature is required to clarify the pathophysiology of deep dyspareunia.

AIMS

To review the pathophysiology of deep dyspareunia, and to propose future research priorities.

METHODS

A narrative review after appraisal of published frameworks and literature search with the terms (dyspareunia AND endometriosis), (dyspareunia AND deep), (dyspareunia AND (pathophysiology OR etiology)).

MAIN OUTCOME VARIABLE

Deep dyspareunia (present/absent or along a pain severity scale).

RESULTS

The narrative review demonstrates potential etiologies for deep dyspareunia, including gynecologic-, urologic-, gastrointestinal-, nervous system-, psychological-, and musculoskeletal system-related disorders. These etiologies can be classified according to anatomic mechanism, such as contact with a tender pouch of Douglas, uterus-cervix, bladder, or pelvic floor, with deep penetration. Etiologies of deep dyspareunia can also be stratified into 4 categories, as previously proposed for endometriosis specifically, to personalize management: type I (primarily gynecologic), type II (nongynecologic comorbid conditions), type III (central sensitization and genito-pelvic pain/penetration disorder), and type IV (mixed). We also identified gaps in the literature, such as lack of a validated patient-reported questionnaire or an objective measurement tool for deep dyspareunia and clinical trials not powered for sexual outcomes.

CONCLUSION

We propose the following research priorities for deep dyspareunia: deep dyspareunia measurement tools, inclusion of the population avoiding intercourse due to deep dyspareunia, nongynecologic conditions in the generation of deep dyspareunia, exploration of sociocultural factors, clinical trials with adequate power for deep dyspareunia outcomes, partner variables, female sexual response, pathways between psychological factors and deep dyspareunia, and personalized approaches to deep dyspareunia. Orr N, Wahl K, Joannou A, et al. Deep Dyspareunia: Review of Pathophysiology and Proposed Future Research Priorities. Sex Med Rev 2020;8:3-17.

Environmental Exposure History and Vulvodynia Risk: A Population-Based Study

BACKGROUND

Risk factors for vulvodynia continue to be elusive. We evaluated the association between past environmental exposures and the presence of vulvodynia.

MATERIALS AND METHODS

The history of 28 lifetime environmental exposures was queried in the longitudinal population-based Woman-to-Woman Health Study on the 24-month follow-up survey. Relationships between these and vulvodynia case status were assessed using multinomial logistic regression.

RESULTS

Overall, 1585 women completed the 24-month survey, the required covariate responses, and questions required for case status assessment. Screening positive as a vulvodynia case was associated with history of exposures to home-sprayed chemicals (insecticides, fungicides, herbicides-odds ratio [OR] 2.47, 95% confidence interval [CI] 1.71-3.58, p < 0.0001), home rodent poison and mothballs (OR 1.62, 95% CI 1.25-2.09, p < 0.001), working with solvents and paints (OR 2.49, 95% CI 1.68-3.70, p < 0.0001), working as a housekeeper/maid (OR 2.07, 95% CI 1.42-3.00, p < 0.0001), working as a manicurist/hairdresser (OR 2.00, 95% CI 1.14-3.53, p < 0.05), and working at a dry cleaning facility (OR 2.13, 95% CI 1.08-4.19, p < 0.05). When classified into nine individual environmental exposure categories and all included in the same model, significant associations remained for four categories (home-sprayed chemicals, home rodent poison or mothballs, paints and solvents, and working as a housekeeper).

CONCLUSIONS

This preliminary evaluation suggests a positive association between vulvodynia and the reported history of exposures to a number of household and work-related environmental toxins. Further investigation of timing and dose of environmental exposures, relationship to clinical course, and treatment outcomes is warranted.

Provoked vestibulodynia: current perspectives

Provoked vestibulodynia (PVD) refers to vulvar pain of at least 3 months duration, localized to the vestibule, provoked by touch and sexual activity and occurring in the absence of a clear identifiable cause. The clinical spectrum ranges from mild with distressing discomfort through to severe and disabling pain. Current understanding is that PVD is one of many chronic pain conditions characterized by sensitization of peripheral and central nociceptive pathways, with pain arising due to dysfunctional neuronal activity in the absence of painful stimuli. Pathophysiology is not well understood but is likely a complex interplay of environmental, genetic, psychological and immune factors. Care is multidisciplinary and follows general principles of chronic pain management with the addition of specific therapy tailored to address pelvic floor overactivity, and sexual and relationship difficulties. More recently, the therapeutic use of placebo is gaining traction in chronic pain research and is a very promising adjunctive therapy. The majority of women with PVD are managed outside of tertiary clinic settings, and care depends on availability and affordability of specialized services; however, much can be done by the primary health provider. PVD is common, and highly treatable, especially with early intervention, but unfortunately, many clinicians are unaware of this condition, and the biggest hurdle for women accessing treatment is obtaining a diagnosis. With treatment, most women can expect significant improvement, often with fairly simple interventions, although some women will benefit from referral to specialized centers. The aims of this article are twofold: firstly, to summarize current literature concerning PVD pathophysiology and management; secondly, to provide a framework for clinicians unfamiliar with vulvar medicine to understand and manage PVD.