Anhedonia to Gentle Touch in Fibromyalgia: Normal Sensory Processing but Abnormal Evaluation

Surveying the International Prevalence and Nature of Eating, Drinking and Swallowing Difficulties in Adults Presenting with Fibromyalgia

Fibromyalgia is a centralized pain syndrome characterized by widespread pain, fatigue, sleep and sensory issues. Fibromyalgia is present in up to 8% of the global population, disproportionally affecting females. Research acknowledges that patients with similar rheumatic/neurological disorders experience eating, drinking and swallowing difficulties. There are also anecdotal reports regarding dysphagia among the fibromyalgia community. However, there is limited research exploring these issues, with potential impact on care delivery and patient outcomes. This study investigated the nature and prevalence of dysphagia in an international sample of adults with fibromyalgia. An online cross-sectional survey design was used to gather data. Questions were adapted from a criterion-based assessment and available evidence. The survey focused on demographics, dysphagia symptoms, and symptom experiences. Results were analyzed using descriptives and correlational analysis. 1983 individuals participated (age range: 18-94), located: Australia (n = 18), Ireland (n = 63), Canada (n = 174), New Zealand (n = 253), the UK (n = 434) and the USA (n = 1024). Many eating, drinking and swallowing symptoms were reported, including food sticking in the throat during swallowing (89%), and pills taking extra effort to swallow (88%), and dry mouth (85%). This study identified previously under-explored eating, drinking and swallowing difficulties among adults with fibromyalgia. These difficulties were self-reported across age, gender, and location, highlighting the potential prevalence of these concerns among a wide range of people, despite having not been explored in depth in previous studies. Timely and accurate dysphagia identification is vital given the its' potential impact on nutrition, prognosis and quality of life. This study highlighted the importance of honoring patient experiences in fibromyalgia management while also recommending input from allied health professionals such as SLTs and dietitians to improve therapeutic relationships and clinical outcomes. As such, continued research into the cause, implications, and management of these issues beyond is required to inform and optimise future patient-centred service delivery and care provision.

Bodily maps of emotions and pain: tactile and hedonic sensitivity in healthy controls and patients experiencing chronic pain

ABSTRACT

Pain is an unpleasant sensory and emotional experience. Both pain and emotions are warning signals against outside harm. Interoception, bodily sensations of emotions can be assessed with the emBODY tool where participants colour the body parts where they feel different emotions. Bodily maps of emotions (BMoE) have been shown to be similar between healthy individuals independent of age, sex, cultural background, and language. We used this tool to analyze how these body maps may differ between healthy controls and patients with persistent pain. We recruited 118 patients with chronic pain. An algorithm-selected matched controls from 2348 individuals who were recruited through social media, message boards, and student mailing lists. After providing background information, the participants completed the bodily topography colouring tasks with the emBODY tool using tablets (patients) and online using their own devices (controls), for pain, sensitivity for tactile, nociceptive and hedonic stimuli, and for the 6 basic emotions and a neutral state. Patients with pain coloured significantly larger areas for pain and more negative emotions. On the whole, their BMoEs were dampened compared with healthy controls. They also coloured more areas for nociceptive but not for tactile or hedonic sensitivity. Patients and controls marked different body areas as sensitive to nociceptive and tactile stimulation, but there was no difference in sensitivity to hedonic touch. Our findings suggest that emotional processing changes when pain persists, and this can be assessed with these colouring tasks. BMoEs may offer a new approach to assessing pain.

A systematic review and meta-analysis of voxel-based morphometric studies of fibromyalgia

Objective

Although neuroimaging investigations have revealed significant changes in brain structure in fibromyalgia (FM) patients, these findings are inconsistent. The current study conducted a systematic review and meta-analysis of voxel-based morphometric studies in order to comprehend those alterations in brain structure in FM patients.

Methods

Voxel-based morphometric (VBM) studies published up to January 17, 2023 were searched in the Web of Science, PubMed, EMBASE, Cochrane Library (CENTRAL), China National Knowledge Infrastructure (CNKI), Chongqing VIP, Wanfang Database. Two independent researchers carried out study screening, quality assessment, clinical data and neuroimaging data extraction. The whole-brain voxel-based gray matter (GM) data of FM patients were collected from eligible studies, and meta-analyzed using anisotropic effect size-signed differential mapping (AES-SDM).

Results

Twelve researches were included in this study, including 289 FM patients (mean age: 47.36 years) and 272 HS (mean age: 47.34 years). According to the meta-analysis, FM patients had increased GM in the right postcentral gyrus and left angular gyrus, and decreased GM in the right cingulate gyrus, right paracingulate gyrus, left cerebellum, and left gyrus rectus.

Conclusion

Our study suggests that fibromyalgia patients have altered gray matter in several brain regions that are involved in affective, cognitive functions, and in motor adaptations to pain processing.

The perception of affective and discriminative touch in blind individuals

Enhanced tactile acuity in blindness is among the most widely reported results of neuroplasticity following prolonged visual deprivation. However, tactile submodalities other than discriminative touch are profoundly understudied in blind individuals. Here, we examined the influence of blindness on two tactile submodalities, affective and discriminative touch, the former being vital for social functioning and emotional processing. We tested 36 blind individuals and 36 age- and sex-matched sighted volunteers. In Experiment 1, we measured the perception of affective tactile signals by asking participants to rate the pleasantness of touch delivered on the palm (nonhairy skin, sparsely innervated with C tactile [CT] fibers) or the forearm (hairy skin, densely innervated with CT fibers) in a CT-optimal versus a CT-nonoptimal manner using a paradigm grounded in studies on tactile sensory neurophysiology. In Experiment 2, we implemented a classic task assessing discriminative touch abilities, the grating orientation task. We found that blind individuals rated the touch as more pleasant when delivered on the palm than on the forearm, while the opposite pattern was observed for sighted participants, who rated stimulation on the forearm as more pleasant than stimulation on the palm. We also replicated the previous findings showing enhanced discriminative tactile acuity in blind individuals. Altogether, our results suggest that blind individuals might experience affective touch differently than sighted individuals, with relatively greater pleasantness perceived on the palm. These results provide a broader insight into somatosensory perception in blind individuals, for the first time taking into consideration the socioemotional aspect of touch.

Social Touch Reduces Pain Perception—An fMRI Study of Cortical Mechanisms

Unmyelinated low-threshold mechanoreceptors (C-tactile, CT) in the human skin are important for signaling information about hedonic aspects of touch. We have previously reported that CT-targeted brush stroking by means of a robot reduces experimental mechanical pain. To improve the ecological validity of the stimulation, we developed standardized human–human touch gestures for signaling attention and calming. The attention gesture is characterized by tapping of the skin and is perceived as neither pleasant nor unpleasant, i.e., neutral. The calming gesture is characterized by slow stroking of the skin and is perceived as moderately to very pleasant. Furthermore, the attention (tapping) gesture is ineffective, whereas the calming (stroking) gesture is effective in activating CT-afferents. We conducted an fMRI study (n = 32) and capitalized on the previous development of touch gestures. We also developed an MR compatible stimulator for high-precision mechanical pain stimulation of the thenar region of the hand. Skin-to-skin touching (stroking or tapping) was applied and was followed by low and high pain. When the stroking gesture preceded pain, the pain was rated as less intense. When the tapping gesture preceded the pain, the pain was rated as more intense. Individual pain perception related to insula activation, but the activation was not higher for stroking than for tapping in any brain area during the stimulation period. However, during the evaluation period, stronger activation in the periaqueductal gray matter was observed after calming touch compared to after tapping touch. This finding invites speculation that human–human gentle skin stroking, effective in activating CT-afferents, reduced pain through neural processes involving CT-afferents and the descending pain pathway.

Pregabalin and hyperbaric oxygen therapy on pain thresholds and anxio-depressive behaviors in a preclinical fibromyalgia pain model

Fibromyalgia (FM) is a chronic, widespread pain disorder generally of a non-inflammatory nature with many known affective and cognitive comorbidities. There is promise in the implementation of hyperbaric oxygen therapy (HBO₂) for alleviating FM pain and comorbidities, despite no work investigating the efficacy of this treatment in prominent preclinical FM models. This project aimed to investigate the affective components, specifically anhedonia and anxiety, associated with an acidic saline model of FM in rats. We investigated the acidic saline model's ability to produce the sensory component of FM through reduced mechanical thresholds, as well as anxiety-like and avoidance behaviors through measures of open field and place escape/avoidance. We further investigated the use of pregabalin, a known FM therapeutic agent, in reducing negative sensory and affective measures within the model. Results revealed insignificant between-group differences for measures of anxiety, despite animals in the FM condition showing significantly reduced mechanical thresholds. Results further revealed that the acidic saline model was effective in increasing place escape/avoidance behavior among animals in the FM condition, with pregabalin reducing avoidance behaviors. In addition, we investigated the role of HBO₂ [two 60-minute treatments at 2.0 ATA (atmospheres absolute)] in alleviating FM-like pain, anxiety, and anhedonia in the acidic saline model, utilizing mechanical paw withdrawal thresholds, open field, and sucrose preference measures. Results revealed that the acidic saline model produced reduced thresholds indicative of FM-like pain. Data did not provide support for the presence of anxio-depressive comorbidities associated with the FM model. HBO₂ treatment did not significantly increase mechanical thresholds as expected. Future studies should seek to investigate the experimental circumstances within which the acidic saline model produces negative affect alongside hyperalgesia in order to contribute to the development of a multidimensional FM treatment methodology.

Structural imaging studies of patients with chronic pain: an anatomical likelihood estimate meta-analysis

ABSTRACT

Neuroimaging is a powerful tool to investigate potential associations between chronic pain and brain structure. However, the proliferation of studies across diverse chronic pain syndromes and heterogeneous results challenges data integration and interpretation. We conducted a preregistered anatomical likelihood estimate meta-analysis on structural magnetic imaging studies comparing patients with chronic pain and healthy controls. Specifically, we investigated a broad range of measures of brain structure as well as specific alterations in gray matter and cortical thickness. A total of 7849 abstracts of experiments published between January 1, 1990, and April 26, 2021, were identified from 8 databases and evaluated by 2 independent reviewers. Overall, 103 experiments with a total of 5075 participants met the preregistered inclusion criteria. After correction for multiple comparisons using the gold-standard family-wise error correction ( P < 0.05), no significant differences associated with chronic pain were found. However, exploratory analyses using threshold-free cluster enhancement revealed several spatially distributed clusters showing structural alterations in chronic pain. Most of the clusters coincided with regions implicated in nociceptive processing including the amygdala, thalamus, hippocampus, insula, anterior cingulate cortex, and inferior frontal gyrus. Taken together, these results suggest that chronic pain is associated with subtle, spatially distributed alterations of brain structure.

The analgesic power of pleasant touch in individuals with chronic pain: Recent findings and new insights

This mini-review covers recent works on the study of pleasant touch in patients with chronic pain (CP) and its potential use as a treatment. While experiments have demonstrated that pleasant touch, through the activation of CT-afferents and the brain regions involved in its affective value, might reduce the unpleasantness and intensity of induced pain, the interaction between pleasant touch and CP remains under-examined. Some experiments show that CP might disrupt the positive aspects of receiving pleasant touch, while in other studies the perception of pleasantness is preserved. Moreover, only a few attempts have been made to test whether touch can have a modulatory effect on CP, but these results also remain inconclusive. Indeed, while one recent study demonstrated that CT-touch can diminish CP after a short stimulation, another study suggested that pleasant touch might not be sufficient. Future studies should further investigate the psychological and neural interplay between pleasant touch and CP. In the conclusion of this mini-review, we propose a new tool we have recently developed using immersive virtual reality (IVR).

Pain, But Not Physical Activity, Is Associated with Gray Matter Volume Differences in Gulf War Veterans with Chronic Pain

Chronic musculoskeletal pain (CMP) is a significant burden for Persian Gulf War Veterans (GWVs), yet the causes are poorly understood. Brain structure abnormalities are observed in GWVs, however relationships with modifiable lifestyle factors such as physical activity (PA) are unknown. We evaluated gray matter volumes and associations with symptoms, PA, and sedentary time in GWVs with and without CMP. Ninety-eight GWVs (10 females) with CMP and 56 GWVs (7 females) controls completed T1-weighted magnetic resonance imaging, pain and fatigue symptom questionnaires, and PA measurement via actigraphy. Regional gray matter volumes were analyzed using voxel-based morphometry and were compared across groups using analysis of covariance (ANCOVA). Separate multiple linear regression models were used to test associations between PA intensities, sedentary time, symptoms, and gray matter volumes. Familywise cluster error rates were used to control for multiple comparisons (α = 0.05). GWVs with CMP reported greater pain and fatigue symptoms, worse mood, and engaged in less moderate-to-vigorous PA and more sedentary time than healthy GWVs (all p values < 0.05). GWVs with CMP had smaller gray matter volumes in the bilateral insula and larger volumes in the frontal pole (p < 0.05adjusted). Gray matter volumes in the left insula were associated with pain symptoms (r partial = 0.26, -0.29; p < 0.05adjusted). No significant associations were observed for either PA or sedentary time (p > 0.05adjusted). GWVs with CMP had smaller gray matter volumes within a critical brain region of the descending pain processing network and larger volumes within brain regions associated with pain sensation and affective processing, which may reflect pain chronification.SIGNIFICANCE STATEMENT The pathophysiology of chronic pain in Gulf War veterans is understudied and not well understood. In a large sample of Gulf War veterans, we report veterans with chronic musculoskeletal pain have smaller gray matter volumes in brain regions associated with pain regulation and larger volumes in regions associated with pain sensitivity compared with otherwise healthy Gulf War veterans. Gray matter volumes in regions of pain regulation were significantly associated with pain symptoms and encompassed the observed group brain volume differences. These results are suggestive of deficient pain modulation that may contribute to pain chronification.

After-Sensations and Lingering Pain following Examination in Patients with Fibromyalgia Syndrome

Fibromyalgia syndrome (FMS) is a chronic widespread pain condition with mixed peripheral and central contributions. Patients display hypersensitivities to a spectrum of stimuli. Patients' blunt pressure pain thresholds are typically reduced, and sometimes (∼15%) gentle brushstroke induces allodynia. However, after-sensations following these stimuli have not, to our knowledge, been reported. We examined the perception of blunt pressure and 'pleasant touch' in FMS. Patients were first interviewed and completed standard psychometric questionnaires. We then measured their sensitivity to blunt pressure and perception of pleasant touch including after-sensations; patients were followed for five days evaluating lingering pain from blunt pressure. We recruited 51 FMS patients and 16 pain-free controls (HC) at a UK Pain Management Centre. Forty-four patients completed the after-sensation protocol. Most patients reported pain after application of less mechanical pressure than HCs; median arm and leg thresholds were 167 kPa and 233 kPa. Eighty-four percent (31/37) of patients reported ongoing pain at the site of pressure application one day after testing, and 49% (18/37) still perceived pain at five days. After-sensations following brushstroke were common in the FMS group, reported by 77% (34/44) compared to 25% (4/16) of HCs; 34% (15/44) patients, but no HCs, perceived these after-sensations as uncomfortable. For FMS patients who experienced after-sensations, brushstroke-pleasantness ratings were reduced, and skin was often an important site of pain. Pain after blunt pressure assessment typically lingers for several days. After-sensations following brushstroke stimulation is a previously unreported FMS phenomenon. They are associated with tactile anhedonia and may identify a clinically distinct subgroup.

Chronic pain precedes disrupted eating behavior in low-back pain patients

Chronic pain is associated with anhedonia and decreased motivation. These behavioral alterations have been linked to alterations in the limbic brain and could explain the increased risk for obesity in pain patients. The mechanism of these behavioral changes and how they set in in relation to the development of chronic pain remain however poorly understood. Here we asked how eating behavior was affected in low-back pain patients before and after they transitioned to chronic pain, compared to patients whose pain subsided. Additionally, we assessed how the hedonic perception of fat-rich food, which is altered in chronic pain patients, related to the properties of the nucleus accumbens in this patients' population. We hypothesized that the accumbens would be directly implicated in the hedonic processing of fat-rich food in pain patients because of its well-established role in hedonic feeding and fat ingestion, and its emerging role in chronic pain. Accordingly, we used behavioral assays and structural brain imaging to test sub-acute back pain patients (SBP) and healthy control subjects at baseline and at approximately one-year follow-up. We also studied a sample of chronic low-back pain patients (CLBP) at one time point only. We found that SBP patients who recovered at follow-up (SBPr) and CLBP patients showed disrupted eating behaviors. In contrast, SBP patients who persisted in having pain at follow-up (SBPp) showed intact eating behavior. From a neurological standpoint, only SBPp and CLBP patients showed a strong and direct relationship between hedonic perception of fat-rich food and nucleus accumbens volume. This suggests that accumbens alterations observed in SBPp patients in previous works might protect them from hedonic eating disruptions during the early course of the illness. We conclude that disrupted eating behavior specifically sets in after pain chronification and is accompanied by structural changes in the nucleus accumbens.

Bodily Illusions and Motor Imagery in Fibromyalgia

Fibromyalgia (FM) is characterised by chronic, continuous, widespread pain, often associated with a sense of fatigue, non-restorative sleep and physical exhaustion. Due to the nature of this condition and the absence of other neurological issues potentially able to induce disorders in body representations per se, it represents a perfect model since it provides an opportunity to study the relationship between pain and the bodily self. Corporeal illusions were investigated in 60 participants with or without a diagnosis of FM by means of an ad hoc devised interview. In addition, motor imagery was investigated and illusions relating to body part movements and changes in body size, feelings of alienness, and sensations of body parts not belonging to one’s own body (disownership and somatoparaphrenic-like sensations) were found. Crucially, these symptoms do not correlate with any of the clinical measures of pain or functional deficits. The results showed that motor imagery was also impaired, and the severity of the deficits found correlated with the functional impairment of the participant. This indicates that disorders in body representations and motor imagery are part of the clinical expression of FM. However, while motor imagery seems to be linked to reduced autonomy and functional deficits, bodily illusions are independent and potentially represent a concurrent symptom.

Clinical Findings in SMR Neurofeedback Protocol Training in Women with Fibromyalgia Syndrome

Fibromyalgia is related to central sensitization syndrome (CSS) and is associated with chronic pain and a decrease in general health. The aim of this study was to explore how changes in brain patterns of female fibromyalgia patients are shaped by neurofeedback therapy and how it affects pain perception and general health. A quasi-experimental study with pre- and post-tests was carried out with 37 female fibromyalgia patients referred by the Pain Unit of the National Health Service of Spain. The method involved applying a sensorimotor rhythm (SMR) protocol to monitor changes in brain waves under different conditions, taking pre-/post-test measurements of perceived pain, general health and the impact on fibromyalgia. Measures included the Fibromyalgia Impact Questionnaire Revised (FIQR), the Visual Analogue Scale (VAS), the General Health Questionnaire (GHQ-28) and EEG (SMR, theta waves). During therapy, the SMR/theta wave ratio increased significantly and after application of therapy, significant results were observed for the FIQR, VAS and GHQ-28. In conclusion, neurofeedback therapy increases the SMR/theta wave ratio in fibromyalgia, helping to maintain a balance between brain functions. This is associated with the activation of inhibitory processes, which is related to the perceived improvement of pain in fibromyalgia patients.

Disrupted Dorsal Mid-Insula Activation During Interoception Across Psychiatric Disorders

OBJECTIVE

Maintenance of bodily homeostasis relies on interoceptive mechanisms in the brain to predict and regulate bodily state. While altered neural activation during interoception in specific psychiatric disorders has been reported in many studies, it is unclear whether a common neural locus underpins transdiagnostic interoceptive differences.

METHODS

The authors conducted a meta-analysis of neuroimaging studies comparing patients with psychiatric disorders with healthy control subjects to identify brain regions exhibiting convergent disrupted activation during interoception. Bibliographic, neuroimaging, and preprint databases through May 2020 were searched. A total of 306 foci from 33 studies were extracted, which included 610 control subjects and 626 patients with schizophrenia, bipolar or unipolar depression, posttraumatic stress disorder, anxiety, eating disorders, or substance use disorders. Data were pooled using a random-effects model implemented by the activation likelihood estimation algorithm. The preregistered primary outcome was the neuroanatomical location of the convergence of peak voxel coordinates.

RESULTS

Convergent disrupted activation specific to the left dorsal mid-insula was found (Z=4.47, peak coordinates: -36, -2, 14; volume: 928 mm3). Studies directly contributing to the cluster included patients with bipolar disorder, anxiety, major depression, anorexia, and schizophrenia, assessed with task probes including pain, hunger, and interoceptive attention. A series of conjunction analyses against extant meta-analytic data sets revealed that this mid-insula cluster was anatomically distinct from brain regions involved in affective processing and from regions altered by psychological or pharmacological interventions for affective disorders.

CONCLUSIONS

These results reveal transdiagnostic, domain-general differences in interoceptive processing in the left dorsal mid-insula. Disrupted mid-insular activation may represent a neural marker of psychopathology and a putative target for novel interventions.

Low mechano-afferent fibers reduce thermal pain but not pain intensity in CRPS

Background

Human hairy (not glabrous skin) is equipped with a subgroup of C-fibers, the C-tactile (CT) fibers. Those do not mediate pain but affective aspects of touch. CT-fiber-activation reduces experimental pain if they are intact. In this pilot study we investigated pain modulating capacities of CT-afferents in CRPS.

Methods

10 CRPS-patients (mean age 33 years, SEM 3.3) and 11 healthy controls (mean age 43.2 years, SEM 3.9) participated.

CT-targeted-touch (brush stroking, velocity: 3 cm/s) was applied on hairy and glabrous skin on the affected and contralateral limb. Patients rated pleasantness of CT-targeted-touch (anchors: 1 “not pleasant”—4 “very pleasant”) twice daily on 10 days. Pain intensity (NRS: 0 “no pain” – 10 “worst pain imaginable”) was assessed before, 0, 30, 60 and 120 min after each CT-stimulation. To assess sensory changes, quantitative-sensory-testing was performed at the beginning and the end of the trial period.

Results

CT-targeted-touch was felt more pleasant on the healthy compared to the affected limb on hairy (p < 0.001) and glabrous skin (p 0.002), independent of allodynia. In contrast to healthy controls patients felt no difference between stimulating glabrous and hairy skin on the affected limb. Thermal pain thresholds increased after CT-stimulation on the affected limb (cold-pain-threshold: p 0.016; heat-pain-threshold: p 0.033).

Conclusions

CT-stimulation normalizes thermal pain thresholds but has no effect on the overall pain in CRPS. Therefore, pain modulating properties of CT-fibers might be too weak to alter chronic pain in CRPS. Moreover, CT-fibers appear to lose their ability to mediate pleasant aspects of touch in CRPS.

Modulation of Muscle Pain Is Not Somatotopically Restricted: An Experimental Model Using Concurrent Hypertonic-Normal Saline Infusions in Humans

We have previously shown that during muscle pain induced by infusion of hypertonic saline (HS), concurrent application of vibration and gentle brushing to overlying and adjacent skin regions increases the overall pain. In the current study, we focused on muscle-muscle interactions and tested whether HS-induced muscle pain can be modulated by innocuous/sub-perceptual stimulation of adjacent, contralateral, and remote muscles. Psychophysical observations were made in 23 healthy participants. HS (5%) was infused into a forearm muscle (flexor carpi ulnaris) to produce a stable baseline pain. In separate experiments, in each of the three test locations (n = 10 per site)—ipsilateral hand (abductor digiti minimi), contralateral forearm (flexor carpi ulnaris), and contralateral leg (tibialis anterior)—50 μl of 0.9% normal saline (NS) was infused (in triplicate) before, during, and upon cessation of HS-induced muscle pain in the forearm. In the absence of background pain, the infusion of NS was imperceptible to all participants. In the presence of HS-induced pain in the forearm, the concurrent infusion of NS into the ipsilateral hand, contralateral forearm, and contralateral leg increased the overall pain by 16, 12, and 15%, respectively. These effects were significant, reproducible, and time-locked to NS infusions. Further, the NS-evoked increase in pain was almost always ascribed to the forearm where HS was infused with no discernible percept attributed to the sites of NS infusion. Based on these observations, we conclude that intramuscular infusion of HS results in muscle hyperalgesia to sub-perceptual stimulation of muscle afferents in a somatotopically unrestricted manner, indicating the involvement of a central (likely supra-spinal) mechanism.

Exploration of Functional Connectivity Changes Previously Reported in Fibromyalgia and Their Relation to Psychological Distress and Pain Measures

Neural functional connectivity changes in the default mode network (DMN), Central executive network (CEN), and insula have been implicated in fibromyalgia (FM) but stem from a sparse set of small-scale studies with limited power for the investigation of confounding effects. We investigated whether anxiety, depression, pain sensitivity, and pain intensity modulated functional connectivity related to DMN nodes, CEN nodes, and insula. Resting-state functional magnetic resonance imaging data were collected from 31 females with FM and 28 age-matched healthy controls. Connectivity was analysed with a region-based connectivity analysis between DMN nodes in ventromedial prefrontal cortex (vmPFC) and posterior cingulate cortex, CEN nodes in the intraparietal sulcus (IPS), and bilateral insula. FM patients displayed significantly higher levels of anxiety and depressive symptoms than controls. The right IPS node of the CEN showed a higher level of connectivity strength with right insula in FM with higher pain intensity compared to controls. More anxiety symptoms in FM correlated with higher levels of connectivity strength between the vmPFC DMN node and right sensorimotor cortex. These findings support the theory of altered insular connectivity in FM and also suggest altered IPS connectivity in FM. Interestingly, no change in insular connectivity with DMN was observed.

Effect of Psycho-Regulatory Massage Therapy on Pain and Depression in Women with Chronic and/or Somatoform Back Pain: A Randomized Controlled Trial

Chronic unspecific back pain (cBP) is often associated with depressive symptoms, negative body perception, and abnormal interoception. Given the general failure of surgery in cBP, treatment guidelines focus on conservative therapies. Neurophysiological evidence indicates that C-tactile fibers associated with the oxytonergic system can be activated by slow superficial stroking of the skin in the back, shoulder, neck, and dorsal limb areas. We hypothesize that, through recruitment of C-tactile fibers, psycho-regulatory massage therapy (PRMT) can reduce pain in patients with cBP. In our study, 66 patients were randomized to PRMT or CMT (classical massage therapy) over a 12-week period and tested by questionnaires regarding pain (HSAL= Hamburger Schmerz Adjektiv Liste; Hamburg Pain adjective list), depression (BDI-II = Beck depression inventory), and disability (ODI = Oswestry Disability Index). In all outcome measures, patients receiving PRMT improved significantly more than did those receiving CMT. The mean values of the HSAL sensory subscale decreased by -51.5% in the PRMT group compared to -6.7% in the CMT group. Depressive symptoms were reduced by -55.69% (PRMT) and -3.1% (CMT), respectively. The results suggest that the superiority of PRMT over CMT may rely on its ability to activate the C-tactile fibers of superficial skin layers, recruiting the oxytonergic system.

Automated Nociceptive Withdrawal Reflex Measurements Reveal Normal Reflex Thresholds and Augmented Pain Ratings in Patients with Fibromyalgia

The nociceptive withdrawal reflex (NWR) is used to probe spinal cord excitability in chronic pain states. Here, we used an automated and unbiased procedure for determining the NWR threshold and compared the reflex thresholds and corresponding pain ratings in a well-characterized cohort of fibromyalgia (n = 29) and matched healthy controls (n = 21). Surface electrical stimuli were delivered to the foot in a stepwise incremental and decremental manner. The surface electromyographic activity was recorded from the ipsilateral tibialis anterior muscle. Fibromyalgia patients reported significantly higher scores for psychological distress and pain-related disability and a significantly lower score for perceived state of health compared to the matched controls. The subjective pain ratings were significantly higher in patients. The NWR thresholds were similar to the controls. In the patients, but not in controls, the NWR thresholds and subjective pain ratings were significantly correlated. Our results showed an increased subjective pain sensitivity in fibromyalgia, but we found no evidence for spinal sensitization based on the reflex measures.