Psychological stress in early life as a predisposing factor for the development of chronic pain: Clinical and preclinical evidence and neurobiological mechanisms

Psychological, social and biological correlates of body perception disturbance in complex regional pain syndrome

Body Perception Disturbance (BPD) in Complex Regional Pain Syndrome (CRPS) still represents a poorly understood phenomenon. Research has shown that knowledge about changes in body perception can yield relevant information for understanding and treating the disease. This study addressed possible connections between BPD and psychological and social factors, pain intensity, and disease duration. Sixty patients with chronic CRPS Type I of the hand were recruited. Body Perception Disturbance was assessed using the Galer and Jensen Neurobehavioral Questionnaire (GJ) and the BATH CRPS Body Perception Disturbance Scale (BATH). Depression, anxiety, stress, childhood trauma and other life events were assessed using standardized and validated questionnaires. This study found that BPD in CRPS was significantly correlated with measures of depression, anxiety, current stress, quality of life, and pain intensity, but not with stress experienced in the twelve months preceding onset of illness, childhood trauma, or duration of illness. Future research needs to identify which patients are most likely to develop these psychological conditions of CRPS, so that early, preventive intervention is possible. This study establishes a relationship between depression, anxiety, current stress, quality of life, pain intensity, and BPD severity. It also supports literature suggesting that preexisting stress, childhood trauma, and disease duration have no influence on BPD. The findings suggest that there is a bidirectional influence between brain alterations, psychological symptoms, and illness severity.

Early Neonatal Pain-A Review of Clinical and Experimental Implications on Painful Conditions Later in Life

Modern health care has brought our society innumerable benefits but has also introduced the experience of pain very early in life. For example, it is now routine care for newborns to receive various injections or have blood drawn within 24 h of life. For infants who are sick or premature, the pain experiences inherent in the required medical care are frequent and often severe, with neonates requiring intensive care admission encountering approximately fourteen painful procedures daily in the hospital. Given that much of the world has seen a steady increase in preterm births for the last several decades, an ever-growing number of babies experience multiple painful events before even leaving the hospital. These noxious events occur during a critical period of neurodevelopment when the nervous system is very vulnerable due to immaturity and neuroplasticity. Here, we provide a narrative review of the literature pertaining to the idea that early life pain has significant long-term effects on neurosensory, cognition, behavior, pain processing, and health outcomes that persist into childhood and even adulthood. We refer to clinical and pre-clinical studies investigating how early life pain impacts acute pain later in life, focusing on animal model correlates that have been used to better understand this relationship. Current knowledge around the proposed underlying mechanisms responsible for the long-lasting consequences of neonatal pain, its neurobiological and behavioral effects, and its influence on later pain states are discussed. We conclude by highlighting that another important consequence of early life pain may be the impact it has on later chronic pain states-an area of research that has received little attention.

Higher levels of stress and different coping strategies are associated with greater morning and evening fatigue severity in oncology patients receiving chemotherapy

PURPOSE

A cancer diagnosis and associated treatments are stressful experiences for most patients. Patients' perceptions of stress and their use of coping strategies may influence fatigue severity. This study extends our previous work describing distinct profiles of morning (i.e., Very Low, Low, High, and Very High) and evening (i.e., Low, Moderate, High, and Very High) fatigue in oncology patients by evaluating for differences in stress and coping strategies among these fatigue classes.

METHODS

This longitudinal study evaluated for changes in morning and evening fatigue in oncology patients (n = 1332) over two cycles of chemotherapy (CTX). Patients completed measures of cumulative exposure to stressful life events (SLEs) (i.e., the Life Stressor Checklist-Revised), general stress (i.e., Perceived Stress Scale [PSS]), cancer-specific stress (i.e., Impact of Event Scale-Revised [IES-R]), and coping strategies (i.e., Brief Cope). Differences among the latent classes were evaluated using analyses of variance, Kruskal-Wallis, or chi-square tests.

RESULTS

Patients in both the Very High morning and evening fatigue classes reported higher numbers of and a higher impact from previous SLEs and higher PSS scores than the other fatigue classes. The IES-R scores for the Very High morning fatigue class met the criterion for subsyndromal PTSD. Patients in the Very High evening fatigue class used a higher number of engagement coping strategies compared with the Very High morning fatigue class.

CONCLUSIONS

Our findings suggest that interventions to reduce stress and enhance coping warrant investigation to decrease fatigue in patients undergoing CTX.

Enterocolic increase of cannabinoid receptor type 1 and type 2 and clinical improvement after probiotic administration in dogs with chronic signs of colonic dysmotility without mucosal inflammatory changes

BACKGROUND

Colonic dysmotility in dogs can cause different GI signs. Sometimes, histology of enterocolic biopsies does not reveal inflammatory infiltrates or mucosal lesions that are typically associated with clinical disease activity. It is speculated that, similarly to humans, colonic dysmotility may be anxiety-based, although recent data demonstrate that irritable bowel syndrome (IBS) could result from acute infectious enteritis. Specific Lactobacillus spp. strains administered orally in humans induced the expression of μ-opioid and cannabinoid receptors in mucosal enterocytes, modulating intestinal morphine-like analgesic functions. We investigated the potential association of GI signs caused by colonic dysmotility and mucosal expression of cannabinoid receptors in intestinal epithelial cells and the number of mucosal mast cells.

METHODS

Ten to 15 endoscopic biopsies were collected from colonic mucosa of 20 dogs diagnosed with dysmotility disturbances before and after probiotic (Slab51 bacterial blend; Sivoy^® ) administration (3-month period). Number and distribution of mast cells (MCs), and cannabinoid receptor type 1 (CB1) and type 2 (CB2) were evaluated by immunohistochemistry and PCR. Results were compared to data obtained from five clinically healthy dogs (archive samples).

KEY RESULTS

Decreased numbers of MCs (P < .0001) and increased CB1- and CB2-positive epithelial cells (P < .0001) in diseased dogs were positively associated with post-treatment CCECAI scores (P < .0001).

CONCLUSIONS AND INFERENCES

Our results suggest that probiotic administration can reduce signs of colonic dysmotility, possibly due to microbiota modulation and epithelial cell receptor-mediated signaling in intestinal mucosa.

Heightened risk of pain in young adult women with a history of childhood maltreatment: a prospective longitudinal study

A child maltreatment history is reported more frequently among adults with chronic pain compared with the general population; unfortunately, studies have primarily relied upon retrospective maltreatment reports by adults with chronic pain. This prospective study assessed pain symptoms in a cohort of young adult women with a documented history of child maltreatment, compared with a matched cohort of women who did not experience childhood maltreatment. Young women (N = 477) were recruited between ages 14 to 17 years and followed annually to age 19. Of these women, 57% experienced maltreatment (ie, physical, sexual, or emotional abuse, neglect; n = 273) substantiated by child welfare record. Maltreated women were demographically matched to nonmaltreated women, also confirmed by child welfare record. In adolescence, post-traumatic stress was assessed. Women were contacted as young adults (Mage = 24.76; n = 383) and surveyed about their pain experiences, including the presence of pain in the past week, pain severity (0-10), and number of body areas with pain. Mediation path analyses examining the impact of maltreatment and adolescent post-traumatic stress on young adult pain were estimated through structural equation modeling. As adults, women who had experienced child maltreatment reported higher pain intensity, a greater number of pain locations, and were more likely to experience pain in the previous week than nonmaltreated women. Adolescent post-traumatic stress partially explained the effects of maltreatment on pain. Young adult women who experienced child maltreatment are at higher risk of pain, particularly when they also experienced post-traumatic stress as adolescents.

Effect of race on the relationship between child maltreatment and obesity in Whites and Blacks

This cross-sectional study was designed to determine what role race plays in the relationship between obesity and child maltreatment (CM), which is currently unknown. One hundred fifteen participants successfully completed the study, including Whites (n = 60) and Blacks (n = 55) of both sexes. CM was assessed using the Childhood Trauma Questionnaire. Total fat, trunk/total fat ratio, visceral adipose tissue (VAT), and VAT/trunk ratio, were measured through Dual Energy X-ray Absorptiometry (DXA) and Corescan software estimation. A significant interaction between identifying as White and having a history of CM was found to predict body mass index (BMI) (β = 5.02, p = .025), total fat (kg) (β = 9.81, p = .036), and VAT (kg) (β = 0.542, p = .025), whereas race by itself was an insignificant predictor. An interaction between having history of physical abuse and identifying as White was found to predict BMI (β = 6.993, p = .003), total fat (β = 12.683, p = .010), and VAT (β = 0.591, p = .018). An interaction between having multiple CM subtypes and identifying as White predicts increased total fat (β = 5.667, p = .034) and VAT (β = 0.335, p = .014). Our findings indicate that the relationship between CM and obesity, measured through BMI, total body fat, and VAT, is seen in Whites but not in Blacks. Future research should investigate the nature of this racial influence to guide obesity prevention and target at-risk populations.

Central Nervous System Changes in Pelvic Inflammation/Pain Patients

Purpose of Review

Centralized pain syndromes (CPS), including chronic pelvic pain (CPP) syndrome, are significant public health problems with prevalence more than diabetes, cancer, or cardiovascular disease. A variety of pathologies are linked with CPP syndrome; however, pain often continues without the presence of pathology, or when an underlying pelvic disease is found, the extent and severity of pain are disproportionate. Although this is not a systematic review, we performed a detailed literature search to identify relevant papers and to provide the available evidence for central changes in association with CPP syndrome.

Recent Findings

Recent advances in brain imaging techniques have provided more accurate data on gray matter volume, functional connectivity, and metabolite levels in the pain-relevant areas of the brain. The present evidence shows that like other chronic pain conditions, the CPP syndrome is associated with central nervous system (CNS) alterations. In particular, these include changes in brain structure, in the activity of both the hypothalamic–pituitary–adrenal (HPA) axis and the autonomic nervous system, and in the behavioral and central response to noxious stimulation.

Summary

A growing body of evidence, mostly from neuroimaging, suggests that for many patients with CPP, the pain may be associated to changes in both structure and function of the CNS. The treatment of pain symptoms, even without the presence of identifiable pathology, may prevent the development or at least minimize the progression of long-term central changes. These findings support the use of new therapeutic strategies targeting the CNS for controlling of pain in CPP conditions.

Early-life programming of pain sensation? Spinal pain in pre-adolescents with pain experience in early life

Neurobiological mechanisms can be involved in early programming of pain sensitization. We aimed to investigate the association between early-life pain experience and pre-adolescence spinal pain. We conducted a study of 29,861 pre-adolescents (age 11-14) from the Danish National Birth Cohort. As indicators of early-life pain, we used infantile colic and recurrent otitis media, reported by mothers when their children were 6 and 18 months. Self-reported spinal pain (neck, middle back, and/or low back pain) was obtained in the 11-year follow-up, classified according to severity. Associations between early-life pain and spinal pain in pre-adolescents were estimated using multinomial logistic regression models. To account for sample selection, inverse probability weighting was applied. Children experiencing pain in early life were more likely to report severe spinal pain in pre-adolescence. The association appeared stronger with exposure to two pain exposures (relative risk ratio, 1.31; 95% CI, 1.02-1.68) rather than one (relative risk ratio, 1.14; 95% CI, 1.05-1.24). We observed similar results when using headache and abdominal pain as outcome measures, underpinning a potential neurobiological or psychosocial link in programming of pain sensitization.Conclusion: Experience of early-life pain is seemingly associated with spinal pain in pre-adolescence. The study highlights that early-life painful experiences can influence programming of future pain responses.What is Known:• Spinal pain in pre-adolescents is common, causes marked discomfort and impairment in everyday life, and may be an important predictor of spinal pain later in life.• Neurobiological mechanisms have been suggested as involved in early programming of pain sensitization.What is New:• Pain exposure in early postnatal life in terms of infantile colic and recurrent otitis media is associated with spinal pain in pre-adolescence; thus, experience of such painful conditions in the early postnatal period may seemingly influence programming of future pain sensation.

Fibromyalgia and dissociative symptoms

BACKGROUND

Fibromyalgia (FM) is a chronic pain syndrome with a controversial etiopathogenesis. Patients with FM usually complain of cognitive symptoms, which are described as "fibrofog." These cognitive complaints might be caused partially by dissociative disorders (DD). The aim of this research is to determine the association between FM and DD.

METHODS

The authors conducted a case-control study for this purpose, integrated by 3 groups: control (C), patients with rheumatic disorders (R), and patients with FM (FM), who were compared through the Dissociative Experiences Scale (DES).The findings are as follows: 42% were taking medications in the FM group, and their differences in scores with those who were not under medications were then considered. In terms of the results, the FM group showed higher scores than both C and R groups (p < 0.05). Patients with FM who were taking antidepressants had lower scores than those who were not (Z-score -8.03; p < 0.05); and finally, 5.71% had a score over 30 (χ2 = 3.73, p = 0.15).

CONCLUSION

Patients with FM had higher scores, which might be related to the association of dissociative experiences, lifetime trauma, and victimization. Antidepressants might have some role on dissociative symptoms as well.

Life Expectancy and Mortality Rates in the United States, 1959-2017

Importance

US life expectancy has not kept pace with that of other wealthy countries and is now decreasing.

Objective

To examine vital statistics and review the history of changes in US life expectancy and increasing mortality rates; and to identify potential contributing factors, drawing insights from current literature and an analysis of state-level trends.

Evidence

Life expectancy data for 1959-2016 and cause-specific mortality rates for 1999-2017 were obtained from the US Mortality Database and CDC WONDER, respectively. The analysis focused on midlife deaths (ages 25-64 years), stratified by sex, race/ethnicity, socioeconomic status, and geography (including the 50 states). Published research from January 1990 through August 2019 that examined relevant mortality trends and potential contributory factors was examined.

Findings

Between 1959 and 2016, US life expectancy increased from 69.9 years to 78.9 years but declined for 3 consecutive years after 2014. The recent decrease in US life expectancy culminated a period of increasing cause-specific mortality among adults aged 25 to 64 years that began in the 1990s, ultimately producing an increase in all-cause mortality that began in 2010. During 2010-2017, midlife all-cause mortality rates increased from 328.5 deaths/100 000 to 348.2 deaths/100 000. By 2014, midlife mortality was increasing across all racial groups, caused by drug overdoses, alcohol abuse, suicides, and a diverse list of organ system diseases. The largest relative increases in midlife mortality rates occurred in New England (New Hampshire, 23.3%; Maine, 20.7%; Vermont, 19.9%) and the Ohio Valley (West Virginia, 23.0%; Ohio, 21.6%; Indiana, 14.8%; Kentucky, 14.7%). The increase in midlife mortality during 2010-2017 was associated with an estimated 33 307 excess US deaths, 32.8% of which occurred in 4 Ohio Valley states.

Conclusions and Relevance

US life expectancy increased for most of the past 60 years, but the rate of increase slowed over time and life expectancy decreased after 2014. A major contributor has been an increase in mortality from specific causes (eg, drug overdoses, suicides, organ system diseases) among young and middle-aged adults of all racial groups, with an onset as early as the 1990s and with the largest relative increases occurring in the Ohio Valley and New England. The implications for public health and the economy are substantial, making it vital to understand the underlying causes.

Frequency of cannabis and illicit opioid use among people who use drugs and report chronic pain: A longitudinal analysis

BACKGROUND

Ecological research suggests that increased access to cannabis may facilitate reductions in opioid use and harms, and medical cannabis patients describe the substitution of opioids with cannabis for pain management. However, there is a lack of research using individual-level data to explore this question. We aimed to investigate the longitudinal association between frequency of cannabis use and illicit opioid use among people who use drugs (PWUD) experiencing chronic pain.

METHODS AND FINDINGS

This study included data from people in 2 prospective cohorts of PWUD in Vancouver, Canada, who reported major or persistent pain from June 1, 2014, to December 1, 2017 (n = 1,152). We used descriptive statistics to examine reasons for cannabis use and a multivariable generalized linear mixed-effects model to estimate the relationship between daily (once or more per day) cannabis use and daily illicit opioid use. There were 424 (36.8%) women in the study, and the median age at baseline was 49.3 years (IQR 42.3-54.9). In total, 455 (40%) reported daily illicit opioid use, and 410 (36%) reported daily cannabis use during at least one 6-month follow-up period. The most commonly reported therapeutic reasons for cannabis use were pain (36%), sleep (35%), stress (31%), and nausea (30%). After adjusting for demographic characteristics, substance use, and health-related factors, daily cannabis use was associated with significantly lower odds of daily illicit opioid use (adjusted odds ratio 0.50, 95% CI 0.34-0.74, p < 0.001). Limitations of the study included self-reported measures of substance use and chronic pain, and a lack of data for cannabis preparations, dosages, and modes of administration.

CONCLUSIONS

We observed an independent negative association between frequent cannabis use and frequent illicit opioid use among PWUD with chronic pain. These findings provide longitudinal observational evidence that cannabis may serve as an adjunct to or substitute for illicit opioid use among PWUD with chronic pain.

Endocannabinoid modulation of inflammatory hyperalgesia in the IFN-α mouse model of depression

Depression is a well-recognised effect of long-term treatment with interferon-alpha (IFN-α), a widely used treatment for chronic viral hepatitis and malignancy. In addition to the emotional disturbances, high incidences of painful symptoms such as headache and joint pain have also been reported following IFN-α treatment. The endocannabinoid system plays an important role in emotional and nociceptive processing, however it is unknown whether repeated IFN-α administration induces alterations in this system. The present study investigated nociceptive responding in the IFN-α-induced mouse model of depression and associated changes in the endocannabinoid system. Furthermore, the effects of modulating peripheral endocannabinoid tone on inflammatory pain-related behaviour in the IFN-α model was examined. Repeated IFN-α administration (8000 IU/g/day) to male C57/Bl6 mice increased immobility in the forced swim test and reduced sucrose preference, without altering body weight gain or locomotor activity, confirming development of the depressive-like phenotype. There was no effect of repeated IFN-α administration on latency to respond in the hot plate test on day 4 or 7 of treatment, however, formalin-evoked nociceptive behaviour was significantly increased in IFN-α treated mice following 8 days of IFN-α administration. 2-Arachidonoyl glycerol (2-AG) levels in the periaqueductal grey (PAG) and rostroventromedial medulla (RVM), and anandamide (AEA) levels in the RVM, were significantly increased in IFN-α-, but not saline-, treated mice following formalin administration. There was no change in endocannabinoid levels in the prefrontal cortex, spinal cord or paw tissue between saline- or IFNα-treated mice in the presence or absence of formalin. Furthermore, repeated IFN-α and/or formalin administration did not alter mRNA expression of genes encoding the endocannabinoid catabolic enzymes (fatty acid amide hydrolase or monoacylglycerol lipase) or endocannabinoid receptor targets (CB_1, CB₂ or PPARs) in the brain, spinal cord or paw tissue. Intra plantar administration of PF3845 (1 μg/10 μl) or MJN110 (1 μg/10 μl), inhibitors of AEA and 2-AG catabolism respectively, attenuated formalin-evoked hyperalgesia in IFN-α, but not saline-, treated mice. In summary, increasing peripheral endocannabinoid tone attenuates inflammatory hyperalgesia induced following repeated IFN-α administration. These data provide support for the endocannabinoid system in mediating and modulating heightened pain responding associated with IFNα-induced depression.

Lifestyle and Chronic Pain across the Lifespan: An Inconvenient Truth?

Chronic pain has a tremendous personal and socioeconomic impact and remains difficult to treat. Therefore, it is important to provide an update on the current understanding regarding lifestyle factors in people with chronic pain across the lifespan. Lifestyle factors such as physical (in)activity, sedentary behavior, stress, poor sleep, unhealthy diet, and smoking are associated with chronic pain severity and sustainment. This applies to all age categories, that is, chronic pain across the lifespan. Yet current treatment options often do not or only partly address the many lifestyle factors associated with chronic pain or attempt to address them in a standard format rather than providing an individually tailored multimodal lifestyle intervention. The evidence regarding lifestyle factors is available in adults, but limited in children and older adults having chronic pain, providing important avenues for future research. In conclusion, it is proposed that treatment approaches for people with chronic pain should address all relevant lifestyle factors concomitantly in an individually-tailored multimodal intervention. Ultimately, this should lead to improved outcomes and decrease the psychological and socioeconomic burden of chronic pain. Level of Evidence: IV.

Neurosteroids and neuropathic pain management: Basic evidence and therapeutic perspectives

Complex mechanisms involved in neuropathic pain that represents a major health concern make its management complicated. Because neurosteroids are bioactive steroids endogenously synthesized in the nervous system, including in pain pathways, they appear relevant to develop effective treatments against neuropathic pain. Neurosteroids act in paracrine or autocrine manner through genomic mechanisms and/or via membrane receptors of neurotransmitters that pivotally modulate pain sensation. Basic studies which uncovered a direct link between neuropathic pain symptoms and endogenous neurosteroid production/regulation, paved the way for the investigations of neurosteroid therapeutic potential against pathological pain. Concordantly, antinociceptive properties of synthetic neurosteroids were evidenced in humans and animals. Neurosteroids promote peripheral analgesia mediated by T-type calcium and gamma-aminobutyric acid type A channels, counteract chemotherapy-induced neuropathic pain and ameliorate neuropathic symptoms of injured spinal cord animals by stimulating anti-inflammatory, remyelinating and neuroprotective processes. Together, these data open interesting perspectives for neurosteroid-based strategies to manage/alleviate efficiently neuropathic pain.

Persistence of pain in humans and other mammals

Evolutionary models of chronic pain are relatively undeveloped, but mainly concern dysregulation of an efficient acute defence, or false alarm. Here, a third possibility, mismatch with the modern environment, is examined. In ancestral human and free-living animal environments, survival needs urge a return to activity during recovery, despite pain, but modern environments allow humans and domesticated animals prolonged inactivity after injury. This review uses the research literature to compare humans and other mammals, who share pain neurophysiology, on risk factors for pain persistence, behaviours associated with pain, and responses of conspecifics to behaviours. The mammal populations studied are mainly laboratory rodents in pain research, and farm and companion animals in veterinary research, with observations of captive and free-living primates. Beyond farm animals and rodent models, there is virtually no evidence of chronic pain in other mammals. Since evidence is sparse, it is hard to conclude that it does not occur, but its apparent absence is compatible with the mismatch hypothesis. This article is part of the Theo Murphy meeting issue 'Evolution of mechanisms and behaviour important for pain'.

Biased Competition Favoring Physical Over Emotional Pain: A Possible Explanation for the Link Between Early Adversity and Chronic Pain

BACKGROUND

Early adversity predisposes to chronic pain, but a mechanistic explanation is lacking. Survivors of early adversity with chronic pain often seem impaired in their ability to be aware of, understand, and express distressing emotions such as anger and fear in social contexts. In this context, it has been proposed that pain may at times serve as a "psychic regulator" by preventing awareness of more intolerable emotions.

METHOD

This narrative review builds on the premise that physical pain and emotional pain are conscious experiences that can compete for selective attention. We highlight mechanisms whereby the consequences of early adversity may put emotional pain at a competitive disadvantage. A case history, supportive research findings, and an evidence-based neurobiological model are presented.

RESULTS

Arising from abuse or neglect in childhood, impairments in the adult capacity to attend to and/or conceptualize the emotional meaning of felt distress may be associated with impaired engagement of the default network and impaired top-down modulation of affective response generation processes. Persistent and poorly conceptualized affective distress may be associated with reduced emotion regulation ability, reduced vagal tone, increased inflammation, and amplified nociceptive signals. Attention to physical pain may be reinforced by the temporary reduction in negative emotions that it causes.

CONCLUSIONS

These processes jointly promote biased competition favoring attention to physical pain and away from one's own emotions. They may constitute an unintentional analog of the phenomenon of self-injury in patients with borderline personality disorder in whom the intentional infliction of physical pain serves to downregulate intense emotional distress. Attending to, expressing, and understanding previously unacknowledged psychological distress unrelated to pain may facilitate recovery from chronic pain after early adversity. Mechanistic studies that can validate this clinically derived neurobiological hypothesis are urgently needed.

Non-invasive monitoring of stress biomarkers in the newborn period

The neonatal period is a highly sensitive time span during which stressful experiences may have an influence on later health outcomes. Medical procedures applied to newborn babies during hospitalization are stressors that trigger a physiological and psychological stress response. Stress response has been traditionally evaluated using scores based on behavioural signs such as facial expressions, limb movements, crying, etc., which are subjectively interpreted. Only few studies have employed measurable physiological signs to objectively evaluate the stress response to specific interventions. The aim of this review is to inform of recently developed biochemical methods that allow clinicians to evaluate the stress response to medical procedures performed in the neonatal period in biological samples non-invasively obtained. Stress biomarkers are based on the physiological stress response mediated by the hypophysis-pituitary-adrenal axis and the sympathetic-adreno-medullary systems. Cortisol is at present the most widely employed laboratory determination to measure stress levels. In recent years, sequentially determined salivary cortisol levels have allowed non-invasive monitoring of newborn infants under stressful conditions in the NICU.

Mast Cells in Gut and Brain and Their Potential Role as an Emerging Therapeutic Target for Neural Diseases

The mast cells (MCs) are the leader cells of inflammation. They are well known for their involvement on allergic reactions through degranulation and release of vasoactive, inflammatory, and nociceptive mediators. Upon encountering potential danger signal, MCs are true sensors of the environment, the first to respond in rapid and selective manner. The MC activates the algic response and modulates the evolution of nociceptive pain, typical of acute inflammation, to neuropathic pain, typical not only of chronic inflammation but also of the dysregulation of the pain system. Yet, MC may contribute to modulate intensity of the associated depressive and anxiogenic component on the neuronal and microglial biological front. Chronic inflammation is a common mediator of these co-morbidities. In parallel to the removal of the etiological factors of tissue damage, the modulation of MC hyperactivity and the reduction of the release of inflammatory factors may constitute a new frontier of pharmacological intervention aimed at preventing the chronicity of inflammation, the evolution of pain, and also the worsening of the depression and anxiogenic state associated with it. So, identifying specific molecules able to modify MC activity may be an important therapeutic tool. Various preclinical evidences suggest that the intestinal microbiota contributes substantially to mood and behavioral disorders. In humans, conditions of the microbiota have been linked to stress, anxiety, depression, and pain. MC is likely the crucial neuroimmune connecting between these components. In this review, the involvement of MCs in pain, stress, and depression is reviewed. We focus on the MC as target that may be mediating stress and mood disorders via microbiota-gut-brain axis.

Fibromyalgia and its New Lessons for Neuropsychiatry

Background

Fibromyalgia (FM) is a centralized pain state that until recently has been shrouded in mystery and questionable as a disease entity in the eyes of many physicians, who considered it purely psychogenic. Fibromyalgia is now thought of as a discrete diagnosis with a clustering of symptoms characterized by central nervous system pain amplification along with anergia, memory loss, disturbances of mood, and sleep disruption. The condition is present in approximately 2% to 8% of the population.

Material/Methods

We review the link between inflammatory mechanisms and FM from a neuropsychiatric perspective.

Results

Recent studies are pointing to a neuroinflammatory etiology that may open up more effective treatment strategies in the future.

Conclusions

Better conceptualization of FM may also elucidate a neuropsychiatric understanding of how nociception, dysthymia, and suicidality co-develop and feed off one another.

The relationship between childhood emotional abuse and chronic pain among people who inject drugs in Vancouver, Canada

BACKGROUND

People who inject drugs (PWID) often contend with chronic pain as a result of illness and trauma, and such pain is known to have significant impacts on mental health, quality of life, and substance use behaviours. Although PWID are also known to have high rates of childhood trauma, little is known about how childhood emotional abuse may be associated with chronic pain in this population.

OBJECTIVE

We undertook this study to explore emotional abuse and chronic pain among PWID.

PARTICIPANTS AND SETTING

This study comprised a total of 1459 participants in Vancouver, Canada between June 2014 and November 2016.

METHODS

We employed multivariable generalized estimating equations with data derived from two prospective cohort studies of community-recruited PWID to examine the relationship between childhood emotional abuse and chronic pain in the past six months.

RESULTS

Among eligible participants, 591 (40.5%) reported childhood emotional abuse, and 760 (52.1%) reported chronic pain in the previous six months. In a multivariable analysis, experiencing childhood emotional abuse remained independently associated with chronic pain (adjusted odds ratio: 1.25; 95% confidence interval: 1.01-1.53) after adjustment for a range of socio-demographic and drug use confounders.

CONCLUSIONS

Our findings suggest that childhood emotional abuse may have lasting relationships with chronic pain among PWID, potentially through established physiological and psychological mechanisms. Current chronic pain treatment may benefit from the evaluation of life course vulnerabilities that may be amenable to earlier interventions. Further, increased availability of effective trauma-informed chronic pain treatment is needed among this vulnerable population.

The role of psychological factors in pediatric functional abdominal pain disorders

BACKGROUND

Pediatric functional abdominal pain disorders (FAPDs) are disorders of brain-gut dysregulation. Psychological factors are known to be related to etiology, maintenance, and exacerbation of pediatric FAPDs. With the evolving literature in the past two decades, a better understanding has emerged of precisely which psychological factors are associated with childhood FAPDs.

PURPOSE

This narrative literature review summarizes the literature of both child and parent psychological factors in pediatric FAPD. Where anxiety and depression were major targets in the older literature, present-day focus is increasingly on pain-specific cognitions and coping strategies including disease threat and catastrophizing. In addition, parental reaction to a child's pain is increasingly recognized as an important moderator of a child's outcomes and has become an area for clinical intervention. Screening for these factors and integrative treatment approaches are recommended in childhood FAPD.

Are Magnetic Resonance Imaging Technologies Crucial to Our Understanding of Spinal Conditions?

Persistent spinal (traumatic and nontraumatic) pain is common and contributes to high societal and personal costs globally. There is an acknowledged urgency for new and interdisciplinary approaches to the condition, and soft tissues, including skeletal muscles, the spinal cord, and the brain, are rightly receiving increased attention as important biological contributors. In reaction to the recent suspicion and questioned value of imaging-based findings, this paper serves to recognize the promise that the technological evolution of imaging techniques, and particularly magnetic resonance imaging, is allowing in characterizing previously less visible morphology. We emphasize the value of quantification and data analysis of several contributors in the biopsychosocial model for understanding spinal pain. Further, we highlight emerging evidence regarding the pathobiology of changes to muscle composition (eg, atrophy, fatty infiltration), as well as advancements in neuroimaging and musculoskeletal imaging techniques (eg, fat-water imaging, functional magnetic resonance imaging, diffusion imaging, magnetization transfer imaging) for these important soft tissues. These noninvasive and objective data sources may complement known prognostic factors of poor recovery, patient self-report, diagnostic tests, and the "-omics" fields. When combined, advanced "big-data" analyses may assist in identifying associations previously not considered. Our clinical commentary is supported by empirical findings that may orient future efforts toward collaborative conversation, hypothesis generation, interdisciplinary research, and translation across a number of health fields. Our emphasis is that magnetic resonance imaging technologies and research are crucial to the advancement of our understanding of the complexities of spinal conditions. J Orthop Sports Phys Ther 2019;49(5):320-329. Epub 26 Mar 2019. doi:10.2519/jospt.2019.8793.

A Copernican Approach to Brain Advancement: The Paradigm of Allostatic Orchestration

There are two main paradigms for brain-related science, with different implications for brain-focused intervention or advancement. The paradigm of homeostasis (“stability through constancy,” Walter Cannon), originating from laboratory-based experimental physiology pioneered by Claude Bernard, shows that living systems tend to maintain system functionality in the direction of constancy (or similitude). The aim of physiology is to elucidate the factors that maintain homeostasis, and therapeutics aim to correct abnormal factor functions. The homeostasis paradigm does not formally recognize influences outside its controlled experimental frames and it is variable in its modeling of neural contributions. The paradigm of allostatic orchestration (PAO) extends the principle of allostasis (“stability through change”) as originally put forth by Peter Sterling. The PAO originates from an evolutionary perspective and recognizes that biological set points change in anticipation of changing environments. The brain is the organ of central command, orchestrating cross-system operations to support optimal behavior at the level of the whole organism. Alternative views of blood pressure regulation and posttraumatic stress disorder (PTSD) illustrate differences between the paradigms. For the PAO, complexities of top-down neural effects and environmental context are foundational (not to be “factored out”), and anticipatory regulation is the principle of their interface. The allostatic state represents the integrated totality of brain-body interactions. Health itself is an allostatic state of optimal anticipatory oscillation, hypothesized to relate to the state of criticality, a mathematical point of poise between phases, on the border between order and disorder (or the “edge of chaos”). Diseases are allostatic states of impaired anticipatory oscillations, demonstrated as rigidifications of set points across the brain and body (disease comorbidity). Conciliation of the paradigms is possible, with “reactive homeostasis” resolved as an illusion stemming from the anticipation of environmental monotony. Considerations are presented with respect to implications of the two paradigms for brain-focused intervention or advancement; the hypothesis that the state of criticality is a vehicle for evolutionary processes; concordance with a philosophy of freedom based on ethical individualism as well as self-creativity, non-obsolescence, empowerment, and citizenship; and concluding reflections on the science and ethics of the placebo, and the potential for virtuous cycles of brain-Anthropocene interactions.

Evidence of impaired pain modulation in adolescents with idiopathic scoliosis and chronic back pain

BACKGROUND CONTEXT

Although 40% of adolescent idiopathic scoliosis (AIS) patients present with chronic back pain, the pathophysiology and underlying pain mechanisms remain poorly understood. We hypothesized that development of chronic pain syndrome in AIS is associated with alterations in pain modulatory mechanisms.

PURPOSE

To identify the presence of sensitization in nociceptive pathways and to assess the efficacy of the diffuse noxious inhibitory control in patients with AIS presenting with chronic back pain.

STUDY DESIGN

Cross-sectional study.

PATIENT SAMPLE

Ninety-four patients diagnosed with AIS and chronic back pain.

OUTCOME MEASURES

Quantitative sensory testing (QST) assessed pain modulation and self-reported questionnaires were used to assess pain burden and health-related quality of life.

METHODS

Patients underwent a detailed pain assessment using a standard and validated quantitative sensory testing (QST) protocol. The measurements included mechanical detection thresholds (MDT), pain pressure threshold (PPT), heat pain threshold (HPT), heat tolerance threshold (HTT), and a conditioned pain modulation (CPM) paradigm. Altogether, these tests measured changes in regulation of the neurophysiology underlying the nociceptive processes based on the patient's pain perception. Funding was provided by The Louise and Alan Edwards Foundation and The Shriners Hospitals for Children.

RESULTS

Efficient pain inhibitory response was observed in 51.1% of patients, while 21.3% and 27.7% had sub-optimal and inefficient CPM, respectively. Temporal summation of pain was observed in 11.7% of patients. Significant correlations were observed between deformity severity and pain pressure thresholds (p=.023) and CPM (p=.017), neuropathic pain scores and pain pressure thresholds (p=.015) and temporal summation of pain (p=.047), and heat temperature threshold and pain intensity (p=.048).

CONCLUSIONS

Chronic back pain has an impact in the quality of life of adolescents with idiopathic scoliosis. We demonstrated a high prevalence of impaired pain modulation in this group. The association between deformity severity and somatosensory dysfunction may suggest that spinal deformity can be a trigger for abnormal neuroplastic changes in this population contributing to chronic pain syndrome.

Detection of systemic inflammation in severely impaired chronic pain patients and effects of a multimodal pain rehabilitation program

Background and aims

Recent research indicates a previously unknown low-grade systemic or neurogenic inflammation in groups of chronic pain (CP) patients. Low-grade inflammation may have an important role in symptoms that have previously not been well depicted: widespread pain, tiredness and cognitive dysfunctions frequently seen in severely impaired CP patients. This study aimed to investigate the plasma inflammatory profile in a group of very complex CP patients at baseline and at a 1-year follow-up after participation in a cognitive behavior therapy (CBT)-based multimodal pain rehabilitation program (PRP).

Methods

Blood samples were collected from 52 well-characterized CP patients. Age- and sex-matched healthy blood donors served as controls. The samples were analyzed with a multiple Proximal Extension Analysis allowing a simultaneous analysis of 92 inflammation-related proteins consisting mainly of cytokines, chemokines and growth-factors. At follow-up, 1-year after participation in the RPR samples from 28 patients were analyzed. The results were confirmed by a multi-array technology that allows quantitative estimation.

Results

Clear signs of increased inflammatory activity were detected in the CP patients. Accepting a false discovery rate (FDR) of 5%, there were significant differences in 43/92 inflammatory biomarkers compared with the controls. In three biomarkers (CXCL5, SIRT2, AXIN1) the expression levels were elevated more than eight times. One year after the PRP, with the patients serving as their own controls, a significant decrease in overall inflammatory activity was found.

Conclusions

Our results indicate that the most impaired CP patients suffer from low-grade chronic systemic inflammation not described earlier with this level of detail. The results may have implications for a better understanding of the cluster of co-morbid symptoms described as the “sickness-syndrome” and the wide-spread pain seen in this group of patients. The decrease in inflammatory biomarkers noted at the follow-up after participation in the PRP may reflect the positive effects obtained on somatic and psycho-social mechanisms involved in the inflammatory process by a rehabilitation program. Besides the PRP, no major changes in medication or lifestyle factors were implemented during the same period. To our knowledge, this is the first study reporting that a PRP may induce inflammatory-reducing effects. Further studies are needed to verify the objective findings in CP patients and address the question of causality that remains to be solved.

Implications

The findings offer a new insight into the complicated biological processes underlying CP. It may have implications for the understanding of symptoms collectively described as the “sickness-syndrome” – frequently seen in this group of patients. The lowering of cytokines after the participation in a PRP indicate a new way to evaluate this treatment; by measuring inflammatory biomarkers.

Neuroimmune modulation of pain across the developmental spectrum

Today's treatment for chronic pain is inadequate, and novel targets need to be identified. This requires a better understanding of the mechanisms involved in pain sensitization and chronification. In this review, we discuss how peripheral inflammation, as occurs during an infection, modulates the central pain system. In rodents, neonatal inflammation leads to increased pain sensitivity in adulthood by priming immune components both peripherally and centrally. The excitability of neurons in the spinal cord is also altered by neonatal inflammation and may add to pain sensitization later in life. In adult humans, inflammation modulates pain sensitivity as well, partly by affecting the activity in brain areas that process and regulate pain signals. Low-grade inflammation is common in clinical populations both peripherally and centrally, and priming of the immune system has also been suggested in some pain populations. The nociceptive and immune systems are primed by infections and inflammation. The early life programming of nociceptive responses following exposure to infections or inflammation will define individual differences in adult pain perception. Immune-to-brain mechanisms and neuroimmune pathway need further investigation as they may serve both as predictors and therapeutic targets in chronic pain.

Psychosocial factors associated with poor outcomes after amputation for complex regional pain syndrome type-I

Background

Amputation for longstanding therapy resistant complex regional pain syndrome type-I (CRPS-I) is controversial. Reported results are inconsistent. It is assumed that psychological factors play a role in CRPS-I.

Objective

To explore which psychological factors prior to amputation are associated with poor outcomes after amputation in the case of longstanding therapy resistant CRPS-I.

Methods

Between May 2008 and August 2015, 31 patients with longstanding therapy resistant CRPS-I were amputated. Before the amputation 11 psychological factors were assessed. In 2016, participants had a structured interview by telephone and filled out questionnaires to assess their outcome. In case of a perceived recurrence of CRPS-I a physician visited the patient to examine the symptoms. Associations between psychological factors and poor outcomes were analysed.

Results

Four of the 11 psychological factors were associated with poor outcomes. Regression analyses showed that change in the worst pain in the past week was associated with poor social support (B = 0.3, 95% confidence interval: 0.1;0.6) and intensity of pain before amputation (B = 2.0, 95% confidence interval 0.9;3.0). Patients who reported important improvements in mobility (n = 23) had significantly higher baseline resilience (median 79) compared to those (n = 8) who did not report it (median 69)(Mann-Whitney U, Z = -2.398, p = 0.015). Being involved in a lawsuit prior to amputation was associated with a recurrence in the residual limb (Bruehl criteria). A psychiatric history was associated with recurrence somewhere else (Bruehl criteria).

Conclusion

Poor outcomes of amputation in longstanding therapy resistant CPRS-1 are associated with psychological factors. Outstanding life events are not associated with poor outcome although half of the participants had experienced outstanding life events.

Priming of Adult Incision Response by Early-Life Injury: Neonatal Microglial Inhibition Has Persistent But Sexually Dimorphic Effects in Adult Rats

Neonatal hindpaw incision primes developing spinal nociceptive circuitry, resulting in enhanced hyperalgesia following reinjury in adulthood. Spinal microglia contribute to this persistent effect, and microglial inhibition at the time of adult reincision blocks the enhanced hyperalgesia. Here, we pharmacologically inhibited microglial function with systemic minocycline or intrathecal SB203580 at the time of neonatal incision and evaluated sex-dependent differences following adult reincision. Incision in adult male and female rats induced equivalent hyperalgesia and spinal dorsal horn expression of genes associated with microglial proliferation (Emr1) and transformation to a reactive phenotype (Irf8). In control adults with prior neonatal incision, the enhanced degree and duration of incision-induced hyperalgesia and spinal microglial responses to reincision were equivalent in males and females. However, microglial inhibition at the time of the neonatal incision revealed sex-dependent effects: the persistent mechanical and thermal hyperalgesia following reincision in adulthood was prevented in males but unaffected in females. Similarly, reincision induced Emr1 and Irf8 gene expression was downregulated in males, but not in females, following neonatal incision with minocycline. To evaluate the distribution of reincision hyperalgesia, prior neonatal incision was performed at different body sites. Hyperalgesia was maximal when the same paw was reincised, and was increased following prior incision at ipsilateral, but not contralateral, sites, supporting a segmentally restricted spinal mechanism. These data highlight the contribution of spinal microglial mechanisms to persistent effects of early-life injury in males, and sex-dependent differences in the ability of microglial inhibition to prevent the transition to a persistent pain state span developmental stages.SIGNIFICANCE STATEMENT Following the same surgery, some patients develop persistent pain. Contributory mechanisms are not fully understood, but early-life experience and sex/gender may influence the transition to chronic pain. Surgery and painful procedural interventions in vulnerable preterm neonates are associated with long-term alterations in somatosensory function and pain that differ in males and females. Surgical injury in neonatal rodents primes the developing nociceptive system and enhances reinjury response in adulthood. Neuroimmune interactions are critical mediators of persistent pain, but sex-dependent differences in spinal neuroglial signaling influence the efficacy of microglial inhibitors following adult injury. Neonatal microglial inhibition has beneficial long-term effects on reinjury response in adult males only, emphasizing the importance of evaluating sex-dependent differences at all ages in preclinical studies.

Evaluating psychosocial contributions to chronic pain outcomes

The biopsychosocial model of pain dominates the scientific community's understanding of chronic pain. Indeed, the biopsychosocial approach describes pain and disability as a multidimensional, dynamic integration among physiological, psychological, and social factors that reciprocally influence one another. In this article, we review two categories of studies that evaluate the contributions of psychosocial factors to the experience of chronic pain. First, we consider general psychosocial variables including distress, trauma, and interpersonal factors. Additionally, we discuss pain-specific psychosocial variables including catastrophizing, expectations, and pain-related coping. Together, we present a diverse array of psychological, social, and contextual factors and highlight the need to consider their roles in the development, maintenance, and treatment of chronic pain conditions.

Wired for Threat: Clinical Features of Nervous System Dysregulation in 80 Children

BACKGROUND

The negative effect of perceived stress on health has become a cultural epidemic. Despite many health implications, the clinical impact of stress on the nervous system is not well understood. This case series describes the symptom profiles of 80 children with nervous system dysregulation attributed to maladaptive neuroendocrine responses to stress.

METHODS

We reviewed of 80 children with nervous system dysregulation identified from a single, tertiary care pediatric neurology clinic. Included patients were between five and 17 years of age, with unexplained medical symptoms lasting three months or longer affecting at least four of six neurological domains: (1) somatization, (2) executive function, (3) autonomic function, (4) digestion, (5) sleep, and (6) emotional regulation. Medical symptoms, diagnoses, and detailed social histories were collected.

RESULTS

Of 80 children, 57 were female (71%), 57 were Caucasian (71%), with median age of 14 years. Symptoms had a mean duration of 32 months, and included: 100% somatic symptoms, 100% emotional dysregulation, 92.5% disrupted sleep, 82.5% autonomic dysregulation, 75% executive dysfunction, and 66% digestive problems. Overall, 94% reported chronic or traumatic stressors; adverse childhood experiences were present in 65%.

CONCLUSIONS

Perceived stress impacts many functions of the neuroendocrine system through experience-dependent plasticity, resulting in a constellation of symptoms and functional impairments we describe as nervous system dysregulation. The pathophysiology of these symptoms involves dysregulation of subcortical, hormonal, and autonomic circuits, which remain largely untested. Recognition and understanding of maladaptive neurophysiology in stress-related symptoms has important implications for diagnosis, treatment, and advances in health research.

Epigenetic Programming Effects of Early Life Stress: A Dual-Activation Hypothesis

Epigenetic processes during early brain development can function as 'developmental switches' that contribute to the stability of long-term effects of early environmental influences by programming central feedback mechanisms of the HPA axis and other neural networks. In this thematic review, we summarize accumulated evidence for a dual-activation of stress-related and sensory networks underlying the epigenetic programming effects of early life stress. We discuss findings indicating epigenetic programming of stress-related genes with impact on HPA axis function, the interaction of epigenetic mechanisms with neural activity in stress-related neural networks, epigenetic effects of glucocorticoid exposure, and the impact of stress on sensory development. Based on these findings, we propose that the combined activation of stress-related neural networks and stressor-specific sensory networks leads to both neural and hormonal priming of the epigenetic machinery, which sensitizes these networks for developmental programming effects. This allows stressor-specific adaptations later in life, but may also lead to functional mal-adaptations, depending on timing and intensity of the stressor. Finally, we discuss methodological and clinical implications of the dual-activation hypothesis. We emphasize that, in addition to modifications in stress-related networks, we need to account for functional modifications in sensory networks and their epigenetic underpinnings to elucidate the long-term effects of early life stress.

[Pain is complex!]

Health professionals are confronted daily with the expression of pain feared and/or perceived by patients. Sometimes it can be related to care. In all cases, they strive to to take care of all its components and to prevent it. A doctor, invested in palliative care, offers an interesting perspective of situations and emotions that can be combined to feed a complex painful dimension.

The impact of fibromyalgia syndrome and the role of comorbidity with mood and post-traumatic stress disorder in worsening the quality of life

BACKGROUND:

The aim is to measure the association between fibromyalgia syndrome (FMS) and post-traumatic stress disorder (PTSD), mood and anxiety disorders using reliable psychiatric diagnoses according to Diagnostic and Statistical Manual of Mental Disorders (4th ed.; DSM-IV) and with a case-control design.

METHODS:

Case-control study with cases (71 consecutive female patients with FMS) and controls (284 subjects without FMS), randomly drawn after a gender- and age-matching technique from the database of an epidemiological survey. Psychiatric diagnoses were conducted according to DSM-IV and carried out by clinical staff using a structured interview (Advanced Neuropsychiatric Tools and Assessment Schedule). QoL was measured by Short Form Health Survey (SF-12).

RESULTS:

The lifetime prevalence of major depressive disorder (MDD; 43.7% vs 8.1%, p < .0001), bipolar disorder (BD; 21.1% vs 0.7%, p  < .0001), PTSD (8.4% vs 1.4%, p < .0001) and panic disorder (28.2% vs 5.6%, p < .001) was higher in people with FMS than in controls. People with FMS showed a poorer QoL than controls on the SF-12 (26.43 ± 6.04 vs 37.45 ± 5.80, p < .0001). Those with comorbidity with MDD and BD showed a mean SF-12 score of 24.75 ± 6.31 versus 29.52 ± 4.84 ( N = 25) of people with FMS without any mood disorder ( p = .002). The attributable burden of FMS in worsening QoL was found comparable to that of serious chronic diseases such as multiple sclerosis.

CONCLUSION:

FMS is a disorder that 'in itself' can have a devastating impact on an individual's life. The frequency of the association with major depressive and bipolar disorders increases the impact on the QoL of people with FMS. One of the causes of this association appears to be the extreme vulnerability to chronic stress that this disorder involves. The findings have important clinical significance: the physician must interpret in the right dimension and with dignity the suffering of the people with FMS.

The Effects of Chronic Stress on Migraine Relevant Phenotypes in Male Mice

Migraine is a disabling neurological disorder affecting 12% of the world’s population. Stress is a major reported trigger and exacerbator of migraine. We evaluated the effects of two chronic stress paradigms on migraine relevant phenotypes in male C57Bl/6 mice.

Methods: Fifty six mice were used in a 14 day social defeat stress (SDS) and twenty three mice were used in a 40 day chronic variable stress (CVS) paradigm. Anxiety measures were evaluated using the open field and elevated plus maze (EPM) tests. Migraine relevant phenotypes were evaluated using the nitroglycerin (NTG) and cortical spreading depression (CSD) models.

Results: Stress sensitive SDS mice and chronically stressed CVS mice showed decreased exploration in the open field and reduced time spent in the open arms of the EPM compared to controls. Stress sensitive and resilient SDS mice had increased serum corticosterone levels, and stressed mice in the CVS paradigm had decreased weight gain compared to controls, providing combined behavioral and physiological evidence of a stress response. In the CVS paradigm but not the SDS paradigm, the stressed group showed a significant decrease in baseline mechanical withdrawal threshold compared to controls. All groups showed a significant reduction in withdrawal threshold after treatment with NTG, but the reduction was not larger in SDS or CVS than in controls. Interestingly, stress resilient SDS mice showed a rapid recovery from NTG effects that was not seen in other groups. No difference in CSD frequency or velocity was seen between stress and control mice in either stress paradigms.

Conclusion: We observed distinct effects of stress on generalized pain response, migraine relevant pain, and migraine relevant excitability. CVS but not SDS was associated with a reduced mechanical withdrawal threshold, consistent with a generalized pain response to chronic stress. Neither SDS nor CVS exacerbated phenotypes considered specifically relevant to migraine - withdrawal to NTG, and susceptibility to CSD. However, the significantly reduced response of stress resilient mice to the NTG stimulus may represent a specific migraine-resistant phenotype.

Associations Between Perceived Stress and Chemotherapy-Induced Peripheral Neuropathy and Otoxicity in Adult Cancer Survivors

CONTEXT

The most common adverse effects from neurotoxic chemotherapy are chemotherapy-induced neuropathy (CIPN), hearing loss, and tinnitus. Although associations between perceived stress and persistent pain, hearing loss, and tinnitus are documented, no studies have examined these associations in cancer survivors who received neurotoxic chemotherapy.

OBJECTIVES

In this cross-sectional study, we evaluated for associations between perceived stress and the occurrence of CIPN, hearing loss, and tinnitus, in 623 adult cancer survivors who received platinum and/or taxane compounds.

METHODS

Survivors completed self-report measures of hearing loss, tinnitus, and perceived stress (i.e., Impact of Events Scale-Revised [IES-R]). Separate logistic regression analyses were done for each neurotoxicity to evaluate whether each of the IES-R subscale (i.e., intrusion, avoidance, hyperarousal) and total scores made a significant independent contribution to neurotoxicity group membership.

RESULTS

Of the 623 survivors in this study, 68.4% had CIPN, 34.5% reported hearing loss, and 31.0% reported tinnitus. Older age, higher body mass index, poorer functional status, being born prematurely, cancer diagnosis, and higher intrusion (P = 0.013), hyperarousal (P = 0.014), and total (P = 0.047) IES-R scores were associated with CIPN. Older age, being male, poorer functional status, a worse comorbidity profile, and a higher IES-R hyperarousal (P = 0.007) score were associated with hearing loss. Being male, having less education, a worse comorbidity profile, and a higher IES-R hyperarousal (P = 0.029) score were associated with tinnitus.

CONCLUSION

These findings suggest that increased levels of perceived stress are associated with the most common chemotherapy-induced neurotoxicities.

Potential Mechanisms Underlying Centralized Pain and Emerging Therapeutic Interventions

Centralized pain syndromes are associated with changes within the central nervous system that amplify peripheral input and/or generate the perception of pain in the absence of a noxious stimulus. Examples of idiopathic functional disorders that are often categorized as centralized pain syndromes include fibromyalgia, chronic pelvic pain syndromes, migraine, and temporomandibular disorder. Patients often suffer from widespread pain, associated with more than one specific syndrome, and report fatigue, mood and sleep disturbances, and poor quality of life. The high degree of symptom comorbidity and a lack of definitive underlying etiology make these syndromes notoriously difficult to treat. The main purpose of this review article is to discuss potential mechanisms of centrally-driven pain amplification and how they may contribute to increased comorbidity, poorer pain outcomes, and decreased quality of life in patients diagnosed with centralized pain syndromes, as well as discuss emerging non-pharmacological therapies that improve symptomology associated with these syndromes. Abnormal regulation and output of the hypothalamic-pituitary-adrenal (HPA) axis is commonly associated with centralized pain disorders. The HPA axis is the primary stress response system and its activation results in downstream production of cortisol and a dampening of the immune response. Patients with centralized pain syndromes often present with hyper- or hypocortisolism and evidence of altered downstream signaling from the HPA axis including increased Mast cell (MC) infiltration and activation, which can lead to sensitization of nearby nociceptive afferents. Increased peripheral input via nociceptor activation can lead to “hyperalgesic priming” and/or “wind-up” and eventually to central sensitization through long term potentiation in the central nervous system. Other evidence of central modifications has been observed through brain imaging studies of functional connectivity and magnetic resonance spectroscopy and are shown to contribute to the widespreadness of pain and poor mood in patients with fibromyalgia and chronic urological pain. Non-pharmacological therapeutics, including exercise and cognitive behavioral therapy (CBT), have shown great promise in treating symptoms of centralized pain.

Opioid analgesia and the somatosensory memory of neonatal surgical injury in the adult rat

Background

Nociceptive input during early development can produce somatosensory memory that influences future pain response. Hind-paw incision during the 1st postnatal week in the rat enhances re-incision hyperalgesia in adulthood. We now evaluate its modulation by neonatal analgesia.

Methods

Neonatal rats [Postnatal Day 3 (P3)] received saline, intrathecal morphine 0.1 mg kg−1 (IT), subcutaneous morphine 1 mg kg⁻¹ (SC), or sciatic levobupivacaine block (LA) before and after plantar hind-paw incision (three×2 hourly injections). Six weeks later, behavioural thresholds and electromyography (EMG) measures of re-incision hyperalgesia were compared with an age-matched adult-only incision (IN) group. Morphine effects on spontaneous (conditioned place preference) and evoked (EMG sensitivity) pain after adult incision were compared with prior neonatal incision and saline or morphine groups. The acute neonatal effects of incision and analgesia on behavioural hyperalgesia at P3 were also evaluated.

Results

Adult re-incision hyperalgesia was not prevented by neonatal peri-incision morphine (saline, IT, and SC groups > IN; P<0.05–0.01). Neonatal sciatic block, but not morphine, prevented the enhanced re-incision reflex sensitivity in adulthood (LA < saline and morphine groups, P<0.01; LA vs IN, not significant). Morphine efficacy in adulthood was altered after morphine alone in the neonatal period, but not when administered with neonatal incision. Morphine prevented the acute incision-induced hyperalgesia in neonatal rats, but only sciatic block had a preventive analgesic effect at 24 h.

Conclusions

Long-term effects after neonatal injury highlight the need for preventive strategies. Despite effective analgesia at the time of neonatal incision, morphine as a sole analgesic did not alter the somatosensory memory of early-life surgical injury.

Case report: Percutaneous electrical neural field stimulation in two cases of sympathetically-mediated pain

Background: Fibromyalgia and complex regional pain syndrome (CRPS) are both chronic pain syndromes with pathophysiologic mechanisms related to autonomic nervous system dysregulation and central sensitization.  Both syndromes are considered difficult to treat with conventional pain therapies. Case presentations: Here we describe a female veteran with fibromyalgia and a male veteran with CRPS, both of whom failed multiple pharmacologic, physical and psychological therapies for pain, but responded to percutaneous electrical neural field stimulation (PENFS) targeted at the auricular branches of the cranial nerves. Discussion: While PENFS applied to the body has been previously described for treatment of localized pain, PENFS effects on cranial nerve branches of the ear is not well-known, particularly when used for regional and full-body pain syndromes such as those described here. PENFS of the ear is a minimally-invasive, non-pharmacologic therapy that could lead to improved quality of life and decreased reliance on medication. However, further research is needed to guide clinical application, particularly in complex pain patients.

The management of fibromyalgia from a psychosomatic perspective: an overview

Fibromyalgia (FM) is a central sensitization syndrome characterized by chronic widespread pain. FM is often comorbid with psychiatric disorders, as well as psychological distress that worsens the quality-of-life of people affected. The aim was to collect current evidence about the management of FM from a psychosomatic perspective. The literature was synthesized and summarized in a narrative format. The literature search was carried out in PubMed; review articles, meta-analysis, overview, and guidelines published in the last 10 years written in English were included. Five main topics (Diagnostic criteria of FM; Pathogenesis of chronic widespread pain in FM; Early stress and trauma as predisposing factors for central sensitization; FM and Psychiatric comorbidity; Implications for treatment) were pointed out and discussed. Much evidence underlies the importance of considering and treating the comorbidity of FM with psychiatric disorders and psychological factors that affect pain management. Validation of FM as a central sensitization syndrome by a clinician facilitates therapeutic strategies that involve patients as active participants in the pain management process, likely leading to improved outcomes.

Ethnic Differences in the Effects of Naloxone on Sustained Evoked Pain: A Preliminary Study

Ethnic differences in pain response have been well documented, with non-Hispanic Black (NHB) participants reporting enhanced clinical pain and greater laboratory-evoked pain sensitivity to a variety of quantitative sensory testing (QST) methods compared to non-Hispanic Whites (NHW). One potential mechanism that may contribute to these disparities is differential functioning of endogenous pain-regulatory systems. To evaluate endogenous opioid (EO) mechanisms in pain responses, we examined group differences in response to tonic capsaicin pain following double-blinded crossover administration of saline and the opioid antagonist, naloxone. Ten percent topical capsaicin cream and a thermode were applied to the dorsum of the non-dominant hand, maintaining a constant temperature of 40°C for 90 min. Naloxone (0.1 mg/kg) or saline placebo was administered at the 25 min mark and post-drug pain intensity ratings were obtained every 5 min thereafter. As an index of EO function, blockade effects were derived for each participant, reflecting the difference between mean post-drug pain intensity ratings under the saline versus naloxone conditions, with higher positive scores reflecting greater EO inhibition of pain. Thirty-nine healthy, young individuals (19 non-Hispanic Black [NHB], 20 non-Hispanic White [NHW]) participated. Group difference in EO function were identified, with NHB participants displaying lower EO function scores (mean=-10.8, SD=10.1) as compared to NHW participants (mean=-0.89, SD=11.5; p=0.038). NHB participants experienced significant paradoxical analgesia with naloxone. Thirty five percent of the NHW participants showed a positive blockade effect indicating EO analgesia (i.e., an increase in pain with naloxone), while only 10% of the NHB participants exhibited evidence of EO analgesia. These findings suggest differential functioning of the endogenous opioid pain regulatory system between NHB and NHW participants. Future research is warranted to examine whether these differences contribute to the disparities observed in clinical pain between groups.

An Integrated Model of Chronic Whiplash-Associated Disorder

Synopsis The development of persistent symptoms following whiplash injury from a motor vehicle collision is common and contributes substantially to societal and personal costs. The popular Quebec Task Force classification system of whiplash-associated disorders (WADs) was meant to function as a prognostic and intervention decision aid, but its usefulness has been questioned. Emerging evidence highlights the heterogeneity of WAD by demonstrating physical and psychological impairments that are unique to those who develop persistent symptoms. These impairments are not recognized in the Quebec Task Force classification system. The purpose of this clinical commentary is to describe an integrated model that focuses on how psychological and neurobiological factors interact with, and are influenced by, existing personal and environmental factors to contribute to the development of chronic WAD. The model has been developed through more than 20 years of work in the field, consultation with experts, in-depth synthesis of existing evidence, and new evidence from the authors' own research programs. A subtheme is that a point of convergence currently exists between the psychological, physiological, and social determinants of health literature that can further explain the complex presentation of WAD. The new model is proposed to orient future research toward more interdisciplinary efforts across nontraditional fields, including data scientists and consumers, to clarify the WAD condition. J Orthop Sports Phys Ther 2017;47(7):462-471. Epub 16 Jun 2017. doi:10.2519/jospt.2017.7455.

Lifetime Modulation of the Pain System via Neuroimmune and Neuroendocrine Interactions

Chronic pain is a debilitating condition that still is challenging both clinicians and researchers. Despite intense research, it is still not clear why some individuals develop chronic pain while others do not or how to heal this disease. In this review, we argue for a multisystem approach to understand chronic pain. Pain is not only to be viewed simply as a result of aberrant neuronal activity but also as a result of adverse early-life experiences that impact an individual's endocrine, immune, and nervous systems and changes which in turn program the pain system. First, we give an overview of the ontogeny of the central nervous system, endocrine, and immune systems and their windows of vulnerability. Thereafter, we summarize human and animal findings from our laboratories and others that point to an important role of the endocrine and immune systems in modulating pain sensitivity. Taking "early-life history" into account, together with the past and current immunological and endocrine status of chronic pain patients, is a necessary step to understand chronic pain pathophysiology and assist clinicians in tailoring the best therapeutic approach.