Altered brain connectivity in dysmenorrhea: pain modulation and the motor cortex

OPRM1 A118G polymorphism modulating motor pathway for pain adaptability in women with primary dysmenorrhea

Introduction

Primary dysmenorrhea (PDM) is a common condition among women of reproductive age, characterized by menstrual pain in the absence of any organic causes. Previous research has established a link between the A118G polymorphism in the mu-opioid receptor (OPRM1) gene and pain experience in PDM. Specifically, carriers of the G allele have been found to exhibit maladaptive functional connectivity between the descending pain modulatory system and the motor system in young women with PDM. This study aims to explore the potential relationship between the OPRM1 A118G polymorphism and changes in white matter in young women with PDM.

Methods

The study enrolled 43 individuals with PDM, including 13 AA homozygotes and 30 G allele carriers. Diffusion tensor imaging (DTI) scans were performed during both the menstrual and peri-ovulatory phases, and tract-based spatial statistics (TBSS) and probabilistic tractography were used to explore variations in white matter microstructure related to the OPRM1 A118G polymorphism. The short-form McGill Pain Questionnaire (MPQ) was used to access participants' pain experience during the MEN phase.

Results

Two-way ANOVA on TBSS analysis revealed a significant main effect of genotype, with no phase effect or phase-gene interaction detected. Planned contrast analysis showed that during the menstrual phase, G allele carriers had higher fractional anisotropy (FA) and lower radial diffusivity in the corpus callosum and the left corona radiata compared to AA homozygotes. Tractographic analysis indicated the involvement of the left internal capsule, left corticospinal tract, and bilateral medial motor cortex. Additionally, the mean FA of the corpus callosum and the corona radiata was negatively correlated with MPQ scales in AA homozygotes, but this correlation was not observed in G allele carriers. No significant genotype difference was found during the pain-free peri-ovulary phase.

Discussion

OPRM1 A118G polymorphism may influence the connection between structural integrity and dysmenorrheic pain, where the G allele could impede the pain-regulating effects of the A allele. These novel findings shed light on the underlying mechanisms of both adaptive and maladaptive structural neuroplasticity in PDM, depending on the specific OPRM1 polymorphism.

Application of fMRI techniques in the study of acupuncture for gynecological diseases: A review

Acupuncture therapy, as a characteristic of Chinese medical therapy, has a long history and remarkable effect in the treatment of gynecological diseases, and so far, it has formed a complete treatment system, but its efficacy and mechanism of action remain unclear. Functional magnetic resonance imaging, a visual technique, provides an objective basis for the study of acupuncture in the treatment of gynecological diseases. This paper summarizes the current status of acupuncture in the treatment of gynecological diseases and summarizes the progress of functional magnetic resonance imaging research related to acupuncture in the treatment of gynecological diseases in the past 10 years, mainly including the common types of gynecological diseases in acupuncture clinics, and the commonly used acupuncture points. This study is expected to provide literature support for subsequent research on the central mechanisms of acupuncture in the treatment of gynecological diseases.

Impairments in grip and pinch force accuracy and steadiness in people with osteoarthritis of the hand: A case-control comparison

BACKGROUND

Symptomatic hand osteoarthritis (OA) is severely disabling condition. Limited evidence has focused on force control measures in this population.

OBJECTIVES

It was the aim of the present study to determine whether force matching accuracy and steadiness are impaired in people with hand OA. In addition, the relationship between force control measures (accuracy and steadiness) and measures of hand function and pain in people with symptomatic hand OA was explored.

DESIGN

Case-control study.

METHOD

Sixty-two participants with symptomatic hand OA and 26 healthy pain-free controls undertook an isometric grip and pinch force matching task at 50 % of their maximum voluntary contraction. Average pain hand pain was recorded. In addition, the Disability of the Arm Shoulder and Hand Questionnaire (DASH), and the Functional Index of Hand Osteoarthritis were collected.

RESULTS

Grip force-matching accuracy and steadiness were significantly impaired in the hand OA group compared to controls (P < 0.05). Pinch force-matching error was greater in people with hand OA (P < 0.05), however, pinch force steadiness was not different between groups. There was a learning effect in people with hand OA, with resolution of force matching impairments with task repetition. A small positive correlation was identified between grip force control and the DASH. No association was found between other measures of force control and self-reported measures of function or pain.

CONCLUSIONS

People with hand OA presented with greater impairments in measures of submaximal force control. These were correlated with self-reported hand function but not pain. Future studies may wish to examine whether objective measures of functional performance are related to force-matching error and steadiness.

Abnormal white matter microstructure along the thalamus fiber pathways in women with primary dysmenorrhea

Primary dysmenorrhea (PDM) is a cyclic menstrual pain in the absence of pelvic anomalies, and women with PDM have an increased sensitivity to pain than the internal and external areas associated with menstrual pain. However, the brain abnormality in the ascending pain pathways in dysmenorrhea remains largely unclear. As the thalamus plays a significant role in transmission of nociceptive input, we examined whether white matter microstructure of the thalamus-related fiber tracts obtained by DTI in women with PDM (n = 47) differs from healthy controls. A novel tractography atlas-based analysis method that detects tract integrity and altered microstructural properties along selected fibers was employed. The fiber bundles of interest contained the thalamus- primary somatosensory cortex (SI), thalamus- dorsal anterior cingulate cortex (dACC)/supplementary motor area (SMA), thalamus-insula, and thalamus-ACC. As compared with controls, abnormal white matter microstructures were found along the thalamus-related white matter fiber tracts. Additionally, the intensity of menstrual pain was significantly associated with diffusion measures of thalamus-SI fiber connections. Our study suggested that the thalamus-related pain processing pathways had altered white matter integrity that persisted beyond the time of menstruation, and the white matter microstructure of the thalamus-SI pathways was closely related to menstrual pain in the intensity by women with PDM.

Instant analgesic effect of radial extracorporeal shock wave therapy on primary dysmenorrhoea according to functional magnetic resonance imaging: study protocol for a randomised placebo-controlled trial

BACKGROUND

Primary dysmenorrhoea (PDM) is defined as a series of pain-dominated symptoms during and after menstruation without organic lesions. Nonsteroidal anti-inflammatory drugs and oral contraceptives are usually recommended as first-line therapy for the clinical treatment of PDM, but their widespread long-term application is controversial. Radial extracorporeal shock wave therapy (rESWT) has been widely applied in musculoskeletal rehabilitation because of its secure and noninvasive characteristics and its confirmed effect in improving pain symptoms. This research seeks to explore the efficacy of rESWT for PDM and the changes in brain function of patients with PDM.

METHODS

This clinical research will be a randomised, blind, sham-controlled trial. Thirty-six patients with PDM will be randomly divided into the rESWT group (n = 18) and the sham rESWT group (n = 18). In the rESWT group, treatment will be applied once within 48 h of menstruation at six abdominal myofascial trigger points. The sham rESWT group will receive sham shockwave therapy on the same sites but without energy input. Other dysmenorrhoea-related treatments in both groups will be limited. The main indicators include the short form of the McGill Pain Questionnaire and the Cox Menstrual Symptom Scale. The secondary indicators include the Zung Self-rating Anxiety Scale and Self-rating Depression Scale and functional magnetic resonance imaging (fMRI) changes in brain regions. Results will be evaluated at the screening, at baseline, and before and after treatment, and adverse treatments will be examined. Inter- and intragroup analyses will be performed.

DISCUSSION

This randomised controlled study is designed to explore the immediate efficacy of rESWT for PDM. After rESWT treatment, PDM symptom tests and pain tests, as well as fMRI data, will be investigated for the potential connections between immediate neuroanalgesic mechanisms, which are associated with pain and brain networks. The main results will be used to assess the efficacy of rESWT, and secondary results will focus on improving the neurobiological understanding of disease treatment.

TRIAL REGISTRATION

China Clinical Trial Register, ChiCTR1900020678. Registered on 13 January 2019.

How Does Myofascial Physical Therapy Attenuate Pain in Chronic Pelvic Pain Syndrome?

Background

Chronic pelvic pain syndrome (CPPS) is a multifactorial disorder comprising structural and functional muscular abnormalities, a dysfunctional pain system, and psychological distress. Myofascial physical Therapy (MPT) that is targeted at improving pelvic muscle functioning is considered a first line nonpharmacological treatment for CPPS, although the precise mechanisms that lead to symptoms alleviation have not yet been elucidated.

Purpose

This longitudinal study aimed to examine the local and systemic effects of MPT intervention, including biopsychophysiological processes, among CPPS patients.

Methods

The study included 50 CPPS women. Morphologic assessment of the levator ani and quantitative sensory testing of the pain system were applied alongside with evaluation of pain-related psychological factors using designated questionnaires. All measures were evaluated both before and after MPT in 39 patients. The long-term effects of MPT were evaluated by clinical pain reports obtained at 3 and 9 months following MPT that were compared with a nontreated group of 11 untreated CPPS women.

Results

Along with an improvement in the clinical pain intensity (p = 0.001) and sensitivity to experimental pain tests (p = 0.001) following MPT, the results also indicate that MPT has anatomical, psychological, and social therapeutic effects (p = 0.04; p = 0.001; p = 0.01, respectively). Furthermore, clinical pain evaluation at 3 and 9 months after MPT revealed a significant improvement in women who received treatment (p = 0.001).

Conclusions

The findings of this pilot study suggest multisystemic (direct and indirect anatomical, neurophysiological, and psychological) effects of MPT on the multifactorial pain disorder of CPPS and therefore place MPT as a mechanism-based intervention.

Whole-brain structural magnetic resonance imaging-based classification of primary dysmenorrhea in pain-free phase: a machine learning study

To develop a machine learning model to investigate the discriminative power of whole-brain gray-matter (GM) images derived from primary dysmenorrhea (PDM) women and healthy controls (HCs) during the pain-free phase and further evaluate the predictive ability of contributing features in predicting the variance in menstrual pain intensity. Sixty patients with PDM and 54 matched female HCs were recruited from the local university. All participants underwent the head and pelvic magnetic resonance imaging scans to calculate GM volume and myometrium-apparent diffusion coefficient (ADC) during their periovulatory phase. Questionnaire assessment was also conducted. A support vector machine algorithm was used to develop the classification model. The significance of model performance was determined by the permutation test. Multiple regression analysis was implemented to explore the relationship between discriminative features and intensity of menstrual pain. Demographics and myometrium ADC-based classifications failed to pass the permutation tests. Brain-based classification results demonstrated that 75.44% of subjects were correctly classified, with 83.33% identification of the patients with PDM (P < 0.001). In the regression analysis, demographical indicators and myometrium ADC accounted for a total of 29.37% of the variance in pain intensity. After regressing out these factors, GM features explained 60.33% of the remaining variance. Our results suggested that GM volume can be used to discriminate patients with PDM and HCs during the pain-free phase, and neuroimaging features can further predict the variance in the intensity of menstrual pain, which may provide a potential imaging marker for the assessment of menstrual pain intervention.

Altered amplitude of low-frequency fluctuation and regional cerebral blood flow in females with primary dysmenorrhea: a resting-state fMRI and arterial spin labeling study

Purpose: The current study aimed to explore the central mechanism of primary dysmenorrhea (PD) by investigating the alterations in resting state amplitude of low-frequency fluctuation (ALFF) and regional cerebral blood flow (CBF) between PD patients and healthy controls (HCs). Patients and methods: A total of 34 female subjects including 20 PD patients and 14 HCs underwent resting-state functional magnetic resonance imaging (rs-fMRI) and arterial spin labeling technique (ASL) MRI during menstrual phase. Subsequently, the differences in ALFF and CBF were compared in the two groups. The visual analog scores for pain (VAS-P) and for anxiety (VAS-A) were applied to assess cramping pain and related symptoms in PD patients. Finally, Pearson's correlation analysis was performed to analyze relationships between the neuroimaging findings and clinical characteristics. Results: Compared to HCs, PD patients had decreased ALFF in the right cerebellum posterior lobe, right middle temporal gyrus, right parahippocampal gyrus, right hippocampus, right brainstem and left parietal lobe. In addition, elevated CBF values were observed in the right inferior frontal gyrus, right precentral gyrus, and right superior temporal gyrus. There was no significant correlation between ALFF, CBF values and clinical characteristics including onset age of dysmenorrhea, VAS-A, and VAS-P in PD patients. Conclusion: The preliminary alterations of ALFF and CBF values in PD patients were observed in different pain-related brain regions, which were involved in multiple dimensions of pain and pain modulation. The combination of rs-fMRI and ASL MRI might provide complementary information for a better understanding of the central mechanism in PD.

Gynecologic Health and Disease Research at the Eunice Kennedy Shriver National Institute of Child Health and Human Development: A Scientific Vision

In May 2016, the newly formed Gynecologic Health and Disease Branch in the Eunice Kennedy Shriver National Institute of Child Health and Human Development invited experts to a 2-day meeting aimed at identification of emerging opportunities in gynecologic investigation. Four primary disorders were chosen for emphasis because they represent the majority of the current Gynecologic Health and Disease Branch portfolio: uterine leiomyomas, endometriosis, pelvic floor disorders, and gynecologic pain conditions. Discussions generated a set of seven cross-cutting themes, which encompass both gaps in our current knowledge and potential directions for further research. These themes formed a continuum for understanding these disorders beginning with the need for classification systems, improved understanding of the natural history and etiology of these disorders, development of novel diagnostics, identification of opportunities for prevention, and the generation of new treatments using cutting-edge approaches. Along with these themes, three broad strategies were proposed to facilitate future research. First, investigators should improve utilization of existing research resources and focus on developing new resources to include databases, biospecimen repositories, animal models, and patient cohorts. Second, multidisciplinary scientific partnerships should be strengthened to bring new insights and approaches to gynecologic research. Third, patient and health care provider education must be promoted to ensure timely and accurate diagnosis and optimize treatment of gynecologic disorders. This article provides a summary of the workshop themes and suggestions, several of which have already been implemented through the development of program priorities and funding opportunity announcements aimed at improving women's reproductive health.

Disrupted physical pain sensation by social exclusion in women with dysmenorrhea

Purpose

Dysmenorrhea (DM), which involves both acute and chronic pain, is associated with abnormalities in pain modulation. Previous studies have shown that social pain relies on some of the same neural regions that process physical pain, highlighting a possible physical–social pain overlap. However, evidence suggesting that social pain modulates the sensitivity to physical pain remains controversial. The present study aimed to assess the effects of social pain manipulation on sensitivity to physical pain in DM sufferers and healthy female controls (HC).

Materials and methods

Fifty-nine otherwise healthy patients with DM and 55 HC matched for age, education, calendar age, and gynecological age were randomly assigned to inclusion or exclusion conditions of Cyberball, a virtual ball tossing game used to induce social pain (social exclusion). Pain threshold and pain tolerance in response to nociceptive pressure and cold stimuli were assessed before and after the study condition.

Results

In response to cold stimulation, pain threshold and tolerance significantly reduced in DM compared to HC participants in the inclusion condition, indicating increased pain sensitivity in DM group. However, exclusion increased the pain threshold and tolerance compared to inclusion in DM but decreased pain threshold and tolerance in HC. Neither inclusion nor exclusion altered pressure pain sensitivity in DM, but, after social exclusion, DM participants were more fearful of being evaluated unfavorably. No significant differences were observed in self-esteem scores between DM and HC after both inclusion and exclusion.

Conclusion

We observed altered pain sensation in DM participants in response to social pain manipulation, suggesting that DM not only impacts menstruation but also modulates the perception of pain more generally, especially its affective processes. The present study suggests that the effect of social pain on pain sensation and certain psychometric properties depends on previous pain experience, implicating a reciprocal influence of social and physical pain processes.

The OPRM1 A118G polymorphism modulates the descending pain modulatory system for individual pain experience in young women with primary dysmenorrhea

The mu-opioid receptor (OPRM1) A118G polymorphism underpins different pain sensitivity and opioid-analgesic outcome with unclear effect on the descending pain modulatory system (DPMS). Primary dysmenorrhea (PDM), the most prevalent gynecological problem with clear painful and pain free conditions, serves as a good clinical model of spontaneous pain. The objective of this imaging genetics study was therefore to explore if differences in functional connectivity (FC) of the DPMS between the OPRM1 A118G polymorphisms could provide a possible explanation for the differences in pain experience. Sixty-one subjects with PDM and 65 controls participated in the current study of resting-state functional magnetic resonance imaging (fMRI) during the menstruation and peri-ovulatory phases; blood samples were taken for genotyping. We studied 3 aspects of pain experience, namely, mnemonic pain (recalled overall menstrual pain), present pain (spontaneous menstrual pain), and experimental pain (thermal pain) intensities. We report that G allele carriers, in comparison to AA homozygotes, exhibited functional hypo-connectivity between the anterior cingulate cortex (ACC) and periaqueductal gray (PAG). Furthermore, G allele carriers lost the correlation with spontaneous pain experience and exhibited dysfunctional DPMS by means of PAG-seeded FC dynamics. This OPRM1 A118G-DPMS interaction is one plausible neurological mechanism underlying the individual differences in pain experience.

Dynamic Changes of Functional Pain Connectome in Women with Primary Dysmenorrhea

Primary dysmenorrhea (PDM) is the most prevalent gynecological problem. Many key brain systems are engaged in pain processing. In light of dynamic communication within and between systems (or networks) in shaping pain experience and behavior, the intra-regional functional connectivity (FC) in the hub regions of the systems may be altered and the functional interactions in terms of inter-regional FCs among the networks may be reorganized to cope with the repeated stress of menstrual pain in PDM. Forty-six otherwise healthy PDM subjects and 49 age-matched, healthy female control subjects were enrolled. Intra- and inter-regional FC were assessed using regional homogeneity (ReHo) and ReHo-seeded FC analyses, respectively. PDM women exhibited a trait-related ReHo reduction in the ventromedial prefrontal cortex, part of the default mode network (DMN), during the periovulatory phase. The trait-related hypoconnectivity of DMN-salience network and hyperconnectivity of DMN-executive control network across the menstrual cycle featured a dynamic transition from affective processing of pain salience to cognitive modulation. The altered DMN-sensorimotor network may be an ongoing representation of cumulative menstrual pain. The findings indicate that women with long-term PDM may develop adaptive neuroplasticity and functional reorganization with a network shift from affective processing of salience to the cognitive modulation of pain.