Central sensitization refers to the amplification of pain by central nervous system mechanisms. Classically described as a consequence of ongoing nociceptive input, it is increasingly recognized that central sensitization also occurs independent of peripheral injury or inflammation. Features of central sensitization have been identified in nearly all chronic pain conditions, and it is considered the primary underlying cause of pain in conditions such as fibromyalgia. Central sensitization is characterized in these conditions by widespread pain and multisite hyperalgesia/ allodynia. Co-occurring symptoms include fatigue, mood and cognitive problems, sleep disturbances, and multisensory hypersensitivity. Individuals with central sensitization often report previous exposure to psychosocial or physical stressors, and a higher personal lifetime and family history of pain, with the latter findings supported by genetic studies. Neuroimaging studies of central sensitization show evidence of: changes in brain gray matter in pain processing regions; neurochemical imbalances; and altered resting brain-network connectivity between pronociceptive and antinociceptive brain areas. Immune system abnormalities have also been demonstrated in individuals with central sensitization. The recognition of central sensitization, andwhether it is being driven by ongoing nociceptive input or it is occurring in the absence of a peripheral driver, is critical for effective pain management.

Objective Recent scientific findings have reinvigorated interest in examining the role of γ-aminobutyric acid (GABA), the major inhibitory central nervous system neurotransmitter, in chronic pain conditions. Decreased inhibitory neurotransmission is a proposed mechanism in the pathophysiology of chronic pain syndromes such as fibromyalgia (FM). The purpose of this study was to test the hypothesis that decreased levels of insular and anterior cingulate GABA would be present in FM patients, and that the concentration of this neurotransmitter would be correlated with pressure–pain thresholds. Methods Sixteen FM patients and 17 age- and sex-matched healthy controls underwent pressure–pain testing and a 3T proton magnetic resonance spectroscopy session in which the right anterior insula, right posterior insula, anterior cingulate, and occipital cortex were examined in subjects at rest. Results GABA levels in the right anterior insula were significantly lower in FM patients compared with healthy controls (mean ± SD 1.17 ± 0.24 arbitrary institutional units versus 1.42 ± 0.32 arbitrary institutional units; P = 0.016). There was a trend toward increased GABA levels in the anterior cingulate of FM patients compared with healthy controls (P = 0.06). No significant differences between groups were detected in the posterior insula or occipital cortex (P > 0.05 for all comparisons). Within the right posterior insula, higher levels of GABA were positively correlated with pressure–pain thresholds in the FM patients (Spearman's rho = 0.63; P = 0.02). Conclusion Diminished inhibitory neurotransmission resulting from lower concentrations of GABA within the right anterior insula may play a role in the pathophysiology of FM and other central pain syndromes.

Adverse posttraumatic neuropsychiatric sequelae (APNS) are common among civilian trauma survivors and military veterans. These APNS, as traditionally classified, include posttraumatic stress, post-concussion syndrome, depression, and regional or widespread pain. Traditional classifications have come to hamper scientific progress because they artificially fragment APNS into siloed, syndromic diagnoses unmoored to discrete components of brain functioning and studied in isolation. These limitations in classification and ontology slow the discovery of pathophysiologic mechanisms, biobehavioral markers, risk prediction tools, and preventive/ treatment interventions. Progress in overcoming these limitations has been challenging, because such progress would require studies that both evaluate a broad spectrum of posttraumatic sequelae (to overcome fragmentation) and also perform in-depth biobehavioral evaluation (to index sequelae to domains of brain function). This article summarizes the methods of the Advancing Understanding of RecOvery afteR traumA (AURORA) Study. AURORA conducts a large scale (n = 5,000 target sample) in-depth assessment of APNS development using a state-of-the-art battery of self-report, neurocognitive, physiologic, digital phenotyping, psychophysical, neuroimaging, and genomic assessments, beginning in the early aftermath of trauma and continuing for one year. The goals of AURORA are to achieve improved phenotypes, prediction tools, and understanding of molecular mechanisms to inform the future development and testing of preventive and treatment interventions.

Patients with FM experience increased lifetime levels of psychosocial adversity, trauma, and emotional conflict. To address these risk factors, we developed Emotion Awareness and Expression Therapy (EAET) and tested its benefits against an active control condition, FM Education, and against the field's gold standard intervention for FM, cognitive-behavioral therapy (CBT) for symptom management. Adults with FM (n = 230) formed 40 treatment groups, which were randomized to EAET, CBT, or Education and given eight, 90-min sessions. Patient-reported outcomes were assessed at baseline, post-treatment, and 6-month follow-up (primary endpoint). Retention of patients to follow-up was excellent (90.4%). Intent-to-treat analyses indicated that, although EAET did not differ from FM Education on pain severity (primary outcome), EAET had significantly better outcomes than FM Education on overall symptoms, widespread pain, physical functioning, cognitive dysfunction, anxiety, depression, positive affect, and life satisfaction (between-condition d's ranging from 0.29 to 0.45 SD), and the percentage of patients improving “much/very much” (34.8% vs. 15.4%). EAET did not differ from CBT on the primary or most secondary outcomes, but compared to CBT, EAET led to significantly lower FM symptoms (d = 0.35) and widespread pain (d = 0.37), and a higher percentage of patients achieving 50% pain reduction (22.5% vs. 8.3%). In summary, an intervention targeting emotional awareness and expression related to psychosocial adversity and conflict was well-received, more effective than a basic educational intervention, and had some advantages over CBT on pain. We conclude that EAET should be considered as an additional treatment option for FM.

Endogenous opioid system dysfunction potentially contributes to chronic pain in fibromyalgia (FM), but it is unknown if this dysfunction is related to established neurobiological markers of hyperalgesia. We previously reported that µ-opioid receptor (MOR) availability was reduced in patients with FM as compared with healthy controls in several pain-processing brain regions. In the present study, we compared pain-evoked functional magnetic resonance imaging with endogenous MOR binding and clinical pain ratings in female opioid-naive patients with FM (n = 18) using whole-brain analyses and regions of interest from our previous research. Within antinociceptive brain regions, including the dorsolateral prefrontal cortex (r = 0.81, P < 0.001) and multiple regions of the anterior cingulate cortex (all r > 0.67; all P < 0.02), reduced MOR availability was associated with decreased pain-evoked neural activity. Additionally, reduced MOR availability was associated with lower brain activation in the nucleus accumbens (r = 0.47, P = 0.050). In many of these regions, pain-evoked activity and MOR binding potential were also associated with lower clinical affective pain ratings. These findings are the first to link endogenous opioid system tone to regional pain-evoked brain activity in a clinical pain population. Our data suggest that dysregulation of the endogenous opioid system in FM could lead to less excitation in antinociceptive brain regions by incoming noxious stimulation, resulting in the hyperalgesia and allodynia commonly observed in this population. We propose a conceptual model of affective pain dysregulation in FM.

It is unknown how chronic inflammation impacts the brain. Here, we examined whether higher levels of peripheral inflammation were associated with brain connectivity and structure in 54 rheumatoid arthritis patients using functional and structural MRI. We show that higher levels of inflammation are associated with more positive connections between the inferior parietal lobule (IPL), medial prefrontal cortex, and multiple brain networks, as well as reduced IPL grey matter, and that these patterns of connectivity predicted fatigue, pain and cognitive dysfunction. At a second scan 6 months later, some of the same patterns of connectivity were again associated with higher peripheral inflammation. A graph theoretical analysis of whole-brain functional connectivity revealed a pattern of connections spanning 49 regions, including the IPL and medial frontal cortex, that are associated with peripheral inflammation. These regions may play a critical role in transducing peripheral inflammatory signals to the central changes seen in rheumatoid arthritis.

Pain can be elicited through all mammalian sensory pathways yet cross-modal sensory integration, and its relationship to clinical pain, is largely unexplored. Centralized chronic pain conditions such as fibromyalgia are often associated with symptoms of multisensory hypersensitivity. In the present study, female fibromyalgia patients demonstrated cross-modal hypersensitivity to visual and pressure stimuli compared to age- and sex-matched healthy controls. Functional magnetic resonance imaging (fMRI) revealed that insular activity evoked by an aversive level of visual stimulation was associated with the intensity of fibromyalgia pain. Moreover attenuation of this insular activity by the analgesic pregabalin was accompanied by concomitant reductions in clinical pain. A multivariate classification method using support vector machines (SVM) applied to visual evoked brain activity distinguished fibromyalgia patients from healthy controls with 82% accuracy. A separate SVM classification of treatment effects on visual evoked activity reliably identified when patients were administered pregabalin as compared to placebo. Both SVM analyses identified significant weights within the insular cortex during aversive visual stimulation. These data suggest that abnormal integration of multisensory and pain pathways within the insula may represent a pathophysiological mechanism in some chronic pain conditions, and that insular response to aversive visual stimulation may have utility as a marker for analgesic drug development.

Urologic chronic pelvic pain syndrome (UCPPS), which encompasses interstitial cystitis/bladder pain syndrome and chronic prostatitis/chronic pelvic pain syndrome, is characterized by chronic pain in the pelvic region or genitalia that is often accompanied by urinary frequency and urgency. Despite considerable research, no definite aetiological risk factors or effective treatments have been identified. The Multidisciplinary Approach to the Study of Chronic Pelvic Pain (MAPP) Research Network uses a novel integrated strategy to characterize UCPPS as a systemic disorder that potentially involves multiple aetiologies. The first phase, MAPP I, included >1,000 participants who completed an intensive baseline assessment followed by a 12-month observational follow-up period. MAPP I studies showed that UCPPS pain and urinary symptoms co-vary, with only moderate correlation, and should be evaluated separately and that symptom flares are common and can differ considerably in intensity, duration and influence on quality of life. Longitudinal clinical changes in UCPPS correlated with structural and functional brain changes, and many patients experienced global multisensory hypersensitivity. Additionally, UCPPS symptom profiles were distinguishable by biological correlates, such as immune factors. These findings indicate that patients with UCPPS have objective phenotypic abnormalities and distinct biological characteristics, providing a new foundation for the study and clinical management of UCPPS.