Disease-Related Microstructural Differences in the Brain in Women With Provoked Vestibulodynia

Symptom-associated alterations in functional connectivity in primary and secondary provoked vestibulodynia

ABSTRACT

Primary provoked vestibulodynia (PVD) is marked by the onset of symptoms at first provoking vulvar contact, whereas secondary PVD refers to symptom onset after some period of painless vulvar contact. Different pathophysiological processes are believed to be involved in the development and maintenance of primary PVD and secondary PVD. The primary aim of this study was to test the hypotheses that the resting state functional connectivity of the brain and brain stem regions differs between these subtypes. Deep clinical phenotyping and resting state brain imaging were obtained in a large sample of a women with primary PVD (n = 46), those with secondary PVD (n = 68), and healthy control women (n = 94). The general linear model was used to test for differences in region-to-region resting state functional connectivity and psychosocial and symptom assessments. Direct statistical comparisons by onset type indicated that women with secondary PVD have increased dorsal attention-somatomotor network connectivity, whereas women with primary PVD predominantly show increased intrinsic resting state connectivity within the brain stem and the default mode network. Furthermore, compared with women with primary PVD, those with secondary PVD reported greater incidence of early life sexual abuse, greater pain catastrophizing, greater 24-hour symptom unpleasantness, and less sexual satisfaction. The findings suggest that women with secondary PVD show greater evidence for central amplification of sensory signals, whereas women with primary PVD have alterations in brain stem circuitry responsible for the processing and modulation of ascending and descending peripheral signals.

An Investigation of Descending Pain Modulation in Women With Provoked Vestibulodynia (PVD): Alterations of Spinal Cord and Brainstem Connectivity

The most common subtype of vulvodynia (idiopathic chronic vulvar pain) is provoked vestibulodynia (PVD). Previous imaging studies have shown that women with vulvodynia exhibit increased neural activity in pain-related brain regions (e.g., the secondary somatosensory cortex, insula, dorsal midcingulate, posterior cingulate, and thalamus). However, despite the recognized role of the spinal cord/brainstem in pain modulation, no previous neuroimaging studies of vulvodynia have examined the spinal cord/brainstem. Sixteen women with PVD and sixteen matched Control women underwent a spinal cord/brainstem functional magnetic resonance imaging (fMRI) session consisting of five runs with no painful thermal stimuli (No Pain), interleaved randomly with five runs with calibrated, moderately painful heat stimulation (Pain). Functional connectivity was also assessed in periods before, during, and after, pain stimulation to investigate dynamic variations in pain processing throughout the stimulation paradigm. Functional connectivity in the brainstem and spinal cord for each group was examined using structural equation modeling (SEM) for both Pain and No Pain conditions. Significant connectivity differences during stimulation were identified between PVD and Control groups within pain modulatory regions. Comparisons of Pain and No Pain conditions identified a larger number of connections in the Control group than in the PVD group, both before and during stimulation. The results suggest that women with PVD exhibit altered pain processing and indicate an insufficient response of the pain modulation system. This study is the first to examine the spinal cord/brainstem functional connectivity in women with PVD, and it demonstrates altered connectivity related to pain modulation in the spinal cord/brainstem.

An Investigation of Descending Pain Modulation in Women With Provoked Vestibulodynia: Alterations of Brain Connectivity

Provoked Vestibulodynia (PVD) is the most common vulvodynia subtype (idiopathic chronic vulvar pain). Functional magnetic resonance imaging (fMRI) studies indicate that women with PVD exhibit altered function in a number of pain modulatory regions in response to noxious stimulation, such as in the secondary somatosensory cortex, insula, dorsal midcingulate, posterior cingulate, and thalamus. However, previous neuroimaging studies of PVD have not examined periods of time before and after noxious stimulation or investigated functional connectivity among pain modulatory regions. Fourteen women with PVD and 14 matched Control participants underwent five fMRI runs with no painful stimuli interleaved randomly with five runs with calibrated, moderately painful heat stimuli applied to the thenar eminence. As recent findings indicate that pain processing begins before and continues after painful stimulation, 2-min periods were included in each run before and after the stimulus. Functional brain connectivity was assessed during both trials of Pain and No Pain stimulation for each group using structural equation modeling (SEM). Analyses of variance (ANOVAs) on connectivity values demonstrated significant main effects of study condition, and group, for connectivity among pain modulatory regions. Most of the differences between the Pain and No Pain conditions found only in the PVD group take place before (i.e., thalamus to INS, ACC to S1, thalamus to S1, and thalamus to S2) and after pain stimulation (i.e., INS to amygdala, PPC to S1, and thalamus to S2). Such differences were not observed in the Control group. These findings further support previous results indicating that women with PVD have altered pain processing compared to pain-free women.

Pain Characteristics, Fear-avoidance Variables, and Pelvic Floor Function as Predictors of Treatment Response to Physical Therapy in Women With Provoked Vestibulodynia

OBJECTIVE

The aim was to investigate whether pretreatment pain characteristics, psychological variables, and pelvic floor muscle (PFM) function predict the response to physical therapy (PT) in women with provoked vestibulodynia (PVD).

MATERIALS AND METHODS

One hundred-five women diagnosed with PVD underwent 10 weekly sessions of individual PT comprising education, PFM exercises with biofeedback, manual therapy, and dilators. Treatment outcomes were evaluated at pretreatment, post-treatment, and 6-month follow-up and included pain intensity (numerical rating scale 0 to 10) and sexual function (Female Sexual Function Scale). Multilevel analyses were used to examine the potential predictors of response over time including pain characteristics (PVD subtype, pain duration), psychological variables (fear of pain, pain catastrophizing), and PFM function assessed with a dynamometric speculum (tone, flexibility, and strength).

RESULTS

PVD subtype and PFM tone were significant predictors of greater treatment response for pain intensity reduction. Secondary PVD (ie, pain developed after a period of pain-free intercourse) and lower PFM tone at baseline were both associated with greater reduction in pain intensity after PT and at follow-up. Among the psychological variables, fear of pain was the only significant predictor of better treatment response when assessed through improvement in sexual function, where higher fear of pain at baseline was associated with greater improvement after PT.

DISCUSSION

This study identified PVD secondary subtype, lower PFM tone, and higher fear of pain as significant predictors of better treatment response to PT in women with PVD.

Dysregulation in Sphingolipid Signaling Pathways is Associated With Symptoms and Functional Connectivity of Pain Processing Brain Regions in Provoked Vestibulodynia

Provoked vestibulodynia (PVD) is a chronic pain disorder characterized by local hypersensitivity and severe pain with pressure localized to the vulvar vestibule. Despite decades of study, the lack of identified biomarkers has slowed the development of effective therapies. The primary aim of this study was to use metabolomics to identify novel biochemical mechanisms in vagina and blood underlying brain biomarkers and symptoms in PVD, thereby closing this knowledge gap. Using a cross-sectional case-control observational study design, untargeted and unbiased metabolomic profiling of vaginal fluid and plasma was performed in women with PVD compared to healthy controls. In women with PVD, we also obtained assessments of vulvar pain, vestibular and vaginal muscle tenderness, and 24-hour symptom intensity alongside resting-state brain functional connectivity of brain regions involved in pain processing and modulation. Compared to healthy controls, women with PVD demonstrated differences primarily in vaginal (but not plasma) concentrations of metabolites of the sphingolipid signaling pathways, suggesting localized effects in vagina and vulvar vestibule rather than systemic effects. Our findings reveal that dysregulation of sphingolipid metabolism in PVD is associated with increased vulvar pain and muscle tenderness, sexual dysfunction, and decreased functional connectivity strength in pain processing/modulatory brain regions. This data collectively suggests that alterations in sphingolipid signaling pathways are likely an important molecular biomarker in PVD that could lead to new targets for therapeutic intervention. PERSPECTIVE: This manuscript presents the results of a robust, unbiased molecular assessment of plasma and vaginal fluid samples in women with provoked vestibulodynia compared to healthy controls. The findings suggest that alterations in sphingolipid signaling pathways are associated with symptoms and brain biomarkers and may be an important molecular marker that could provide new targets for therapeutic intervention.

Reduced concentrations of vaginal metabolites involved in steroid hormone biosynthesis are associated with increased vulvar vestibular pain and vaginal muscle tenderness in provoked vestibulodynia: An exploratory metabolomics study

Provoked vestibulodynia (PVD) is a chronic vulvar pain disorder characterized by hypersensitivity and severe pain with pressure localized to the vulvar vestibule. Knowledge regarding pathophysiological mechanisms contributing to the etiology and production of symptoms in PVD remains incomplete but is considered multifactorial. Using a cross-sectional observational study design, data from untargeted metabolomic profiling of vaginal fluid and plasma in women with PVD and healthy women was combined with pain testing and brain imaging in women with PVD to test the hypotheses that women with PVD compared to healthy women show differences in vaginal and plasma metabolites involved in steroid hormone biosynthesis. Steroid hormone metabolites showing group differences were correlated with vulvar vestibular pain and vaginal muscle tenderness and functional connectivity of brain regions involved in pain processing in women with PVD to provide insight into the functional mechanisms linked to the identified alterations. Sensitivity analyses were also performed to determine the impact of hormonal contraceptive use on the study findings. Women with PVD compared to healthy controls had significant reductions primarily in vaginal fluid concentrations of androgenic, pregnenolone and progestin metabolites involved in steroidogenesis, suggesting localized rather than systemic effects in vagina and vulvar vestibule. The observed reductions in androgenic metabolite levels showed large effect size associations with increased vulvar vestibular pain and vulvar muscle tenderness and decreases in androgenic and progestin metabolites were associated with decreased connectivity strength in primary sensorimotor cortices. Women with PVD showed symptom-associated reductions in vaginal fluid concentrations of metabolites involved in the biosynthesis of steroid hormones previously shown to affect the integrity of vulvar and vaginal tissue and nociceptive processing. Deficiency of certain steroids may be an important mechanism contributing to the pathophysiology of symptoms in PVD may provide potential diagnostic markers that could lead to new targets for therapeutic intervention.

Vulvodynia

Vulvodynia is a condition that occurs in 8-10% of women of all ages and is characterized by pain at the vulva that is present during sexual and/or non-sexual situations. Diagnosis is established through careful medical history and pelvic examination, including the cotton-swab test. The onset and maintenance of vulvodynia involves a complex interplay of peripheral and central pain mechanisms, pelvic floor muscle and autonomic dysfunction, anxiety, depression and childhood maltreatment as well as cognitive-affective, behavioural and interpersonal factors. Given the absence of empirically supported treatment guidelines, a stepwise approach of pelvic floor physical therapy and cognitive behavioural therapy as well as medical management is suggested, with surgery as the last option. Vulvodynia has a negative effect on the quality of life of women and their partners, and imposes a profound personal and societal economic burden. In addition, women with vulvodynia are more likely to report other chronic pain conditions, which further alters their quality of life. Future efforts should aim to increase girls', women's and healthcare professionals' education and awareness of vulvodynia, phenotype different subgroups of women based on biopsychosocial characteristics among more diverse samples, conduct longitudinal studies and improve clinical trial designs.

Exploring the neural correlates of touch and pain in women with provoked vestibulodynia

Group differences in touch and pain thresholds-and their neural correlates-were studied in women with provoked vestibulodynia (PVD; N = 15), a common subtype of vulvodynia (chronic vulvar pain), and pain-free control women (N = 15). Results from quantitative sensory testing and self-report measures indicated that, as compared with control participants, women with PVD exhibited allodynia (ie, pain in response to a normally nonpainful stimulus) and hyperalgesia (ie, an increased response to a normally painful stimulus) at vulvar and nonvulvar sites. In addition, brain imaging analyses demonstrated reduced difference scores between touch and pain in the S2 area in women with PVD compared with control participants, supporting previous findings of allodynia in women with PVD. There were no significant reductions in difference scores between touch and pain for regions related to cognitive and affective processing of painful stimuli. The results of this study contribute important information to the general pain and vulvodynia literatures in elucidating the specific sensorimotor neural mechanisms that underlie hyperalgesia in a chronic pain population. These results have implications for differentiating neural processing of touch and pain for women with and without PVD. Future research should attempt to examine alterations related to hyperalgesia in commonly comorbid conditions of PVD.

Altered gray matter volume in sensorimotor and thalamic regions associated with pain in localized provoked vulvodynia: a voxel-based morphometry study

Multimodal neuroimaging studies provide support for a role of alterations in sensory processing circuits and endogenous pain modulatory systems in provoked vestibulodynia (PVD). In this study, we tested the hypotheses that PVD compared with healthy controls (HCs) would demonstrate gray matter volume (GMV) alterations in regions associated with sensorimotor, corticothalamic, and basal ganglia circuits. We also tested the replicability of previously reported gray matter increases in basal ganglia and hippocampal volumes in PVD vs HCs. In addition, disease specificity of GMV alterations were examined by comparing PVD with another chronic pain disorder. Finally, we examine whether GMV alterations are correlated with symptom measures. Structural magnetic resonance imaging was obtained in 119 premenopausal women (45 PVD, 45 HCs, and 29 irritable bowel syndrome [IBS]). A voxel-based morphometry analysis was applied to determine group differences in the hypothesized regions of interest. Compared with HCs, PVD women exhibited greater GMV in the basal ganglia, hippocampus, and sensorimotor cortices. Compared to patients with IBS, women with PVD had greater GMV in the hippocampus, and sensorimotor network, but lower GMV in the thalamus and precentral gyrus. Regional GMV alterations were associated with patient reports of pain during intercourse and muscle tenderness. The current findings provide further evidence that GMV is increased in PVD compared with HCs in several regions of the sensorimotor network and the hippocampus in patients with PVD. In addition, GMV distinct alterations in the sensorimotor network were identified between 2 pelvic pain disorders, PVD compared with IBS.