Sensory Qualities Of Pain Research Articles

Development and evaluation of the patient-reported outcomes measurement information system (PROMIS) pediatric pain quality item bank and short form.

Pain is a common problem among children, particularly those with pediatric chronic diseases. Multifaceted assessment of pain can improve communication about pain and help clinicians characterize, differentiate, and treat a patient's unique experience of pain. Pain quality is an important domain of pain, describing the subjective sensory experiences associated with pain as well as the affective experiences of pain. The aim of the current study was to quantitatively evaluate the measurement properties of the 59 Patient-Reported Outcomes Measurement Information System pediatric pain quality candidate items developed as part of the National Institutes of Health's Patient-Reported Outcomes Measurement Information System initiative with input from children and adolescents with chronic pain. Participants included N = 448 pediatric patients between 8 and 18 years of age with chronic health conditions with a prominent component of chronic or recurrent pain, including juvenile fibromyalgia, juvenile idiopathic arthritis, and sickle cell disease. A confirmatory factor analysis revealed a unidimensional model fit the data best, with 56 of the 59 items demonstrating good psychometric properties for inclusion in the final measure. In addition, a consensus-building method was used to establish 2 versions of a short form measure-one with 8 items focused primarily on the sensory pain qualities and one with 8 items focused on affective pain qualities. The final measure shows good reliability and validity, and is recommended for use in research and clinical care with pediatric populations.

Predicting the Physical and Mental Health Status of Individuals With Chronic Musculoskeletal Pain From a Biopsychosocial Perspective: A Multivariate Approach.

Chronic pain is theoretically conceptualized from a biopsychosocial perspective. However, research into chronic pain still tends to focus on isolated, biological, psychological, or social variables. Simultaneous examination of these variables in the prediction of outcomes is important because communalities between predictors exist. Examination of unique contributions might help guide research and interventions in a more effective way. The participants were 114 individuals with chronic pain (mean age=58.81, SD=11.85; 58.8% women and 41.2% men) who responded to demographics (age and sex), pain characteristics (duration and sensory qualities), psychological (catastrophizing and perceived injustice), and social (marital adjustment) measures. Multivariate analyses were conducted to investigate their unique contributions to pain-related health variables pain severity, pain interference, disability, anxiety, and depressive symptoms. Bivariate analyses evidenced significant associations between pain sensory qualities, catastrophizing, perceived injustice, and all health variables. In multivariate analyses, pain sensory qualities were associated with pain severity (β=0.10; 95% confidence interval [CI]=0.05, 0.14; t=4.28, P<0.001), while perceived injustice was associated with pain interference (β=0.08; 95% CI=0.03, 0.12; t=3.59, P<0.001), disability (β=0.25; 95% CI=0.08, 0.42; t=2.92, P=0.004), anxiety (β=0.18; 95% CI=0.08, 0.27; t=3.65, P<0.001), and depressive symptoms (β=0.14; 95% CI=0.05, 0.23; t=2.92, P=0.004). Age, sex, pain duration, and marital adjustment were not associated with health variables either in bivariate or in multivariate analyses (all P>0.010). As expected, communalities between biopsychosocial variables exist, which resulted in a reduced number of unique contributions in multivariate analyses. Perceived injustice emerged as a unique contributor to variables, which points to this psychological construct as a potentially important therapeutic target in multidisciplinary treatment of pain.

A QST-based Pain Phenotype in Adults With Sickle Cell Disease: Sensitivity and Specificity of Quality Descriptors.

We sought to refine a screening measure for discriminating a sensitized or normal sensation pain phenotype among African American adults with sickle cell disease (SCD). To develop scoring schemes based on sensory pain quality descriptors; evaluate their performance on classifying patients with SCD who had sensitization or normal sensation, and compare with scores on the Self-report Leeds Assessment of Neuropathic Symptoms and Signs (S-LANSS) and the Neuropathic Pain Symptom Inventory (NPSI). Participants completed PAINReportIt, quantitative sensory testing (QST), S-LANSS, and NPSI. Conventional binary logistic regression and least absolute shrinkage and selection operator (lasso) regression were used to obtain 2 sets of weights resulting in 2 scores: the PR-Logistic (PAINReportIt score weighted by conventional binary logistic regression coefficients) and PR-Lasso (PAINReportIt score weighted by lasso regression coefficients). Performance of the proposed scores and the existing scores were evaluated. Lasso regression resulted in a parsimonious model with non-zero weights assigned to 2 neuropathic descriptors, cold and spreading. We found positive correlations between the PR-Lasso and other scores: S-LANSS (r=0.22, P<0.01), NPSI (r=0.22, P<0.01), and PR-Logistic (r=0.35, P<0.01). The NPSI and PR-Lasso performed similarly at different levels of required specificity and outperformed the S-LANSS and PR-Logistic at the various specificity points. The PR-Lasso offers a way to discriminate a SCD pain phenotype.

Relationship of Pain Quality Descriptors and Quantitative Sensory Testing: Sickle Cell Disease.

Chronic pain in adults with sickle cell disease (SCD) may be the result of altered processing in the central nervous system, as indicated by quantitative sensory testing (QST). Sensory pain quality descriptors on the McGill Pain Questionnaire (MPQ) are indicators of typical or altered pain mechanisms but have not been validated with QST-derived classifications. The specific aim of this study was to identify the sensory pain quality descriptors that are associated with the QST-derived normal or sensitized classifications. We expected to find that sets of sensory pain quality descriptors would discriminate the classifications. A cross-sectional quantitative study of existing data from 186 adults of African ancestry with SCD. Variables included MPQ descriptors, patient demographic data, and QST-derived classifications. The participants were classified as central sensitization (n = 33), mixed sensitization (n = 23), and normal sensation. Sensory pain quality descriptors that differed statistically between mixed sensitization and central sensation compared to normal sensitization included cold (p = .01) and spreading (p = .01). Aching (p = .01) and throbbing (p = .01) differed statistically between central sensitization compared with mixed sensitization and normal sensation. Beating (p = .01) differed statistically between mixed sensitization compared with central sensitization and normal sensation. No set of sensory pain quality descriptors differed statistically between QST classifications. Our study is the first to examine the association between MPQ sensory pain quality descriptors and QST-derived classifications in adults with SCD. Our findings provide the basis for the development of a MPQ subscale with potential as a mechanism-based screening tool for neuropathic pain.

(176) New Scoring for Pain Quality Descriptors: Associations with Quantitative Sensory Testing in Adults with Sickle Cell Disease

A simple count of the PAINReportIt® number of neuropathic descriptors (PR-NNP) was only moderately correlated with two other valid neuropathic pain measures. The study aim was to develop a new PR-NNP score that maximizes the accuracy of classifying known groups of patients with sickle cell disease (SCD) who had sensitization or normal sensation and evaluate its associations with scores on the self-report version of the Leeds Assessment of Neuropathic Symptoms and Signs (S-LANSS) and the Neuropathic Pain Symptom Inventory (NPSI). In a cross-sectional, single-session, exploratory study of existing data, 180 adults of African ancestry with SCD completed PAINReportIt® (a computerized version of the McGill Pain Questionnaire), thermal and mechanical quantitative sensory testing (Medoc TSA II), S-LANSS, and NPSI from April 2015 to August 2017. Among the participants, most were female (59%), and ranging in age between 19 to 66 years (mean = 36.5±11.4). Using the number word count to score the PR-NNP sensitivity was 21% and specificity was 89%. We developed a weighted score for the PR-NNP and evaluated its sensitivity and specificity to sensitization or normal sensation groups. We computed weights for the sensory pain quality descriptors using the logarithms of odds ratios as weights. The logarithms of odds ratio provided a score for the PR-NNP with sensitivity=81% and specificity=60%, which was better than the S-LANSS’ sensitivity=44% and specificity=60% and the NPSI's sensitivity=52% and specificity=71%. Our new score offers a pain screening tool to discriminate between groups with sensitization or normal sensation, which is important for healthcare provider decision making for prescription of analgesics and treatment goals. Future research is recommended to strengthen the value of the PR-NNP for discrimination of pain type by inclusion of other dimensions of pain such as pain intensity. Supported by grant number R01HL124945.

An amygdalar neural ensemble that encodes the unpleasantness of pain.

Pain is an unpleasant experience. How the brain’s affective neural circuits attribute this aversive quality to nociceptive information remains unknown. By means of time-lapse in vivo calcium imaging and neural activity manipulation in freely behaving mice encountering noxious stimuli, we identified a distinct neural ensemble in the basolateral amygdala that encodes the negative affective valence of pain. Silencing this nociceptive ensemble alleviated pain affective-motivational behaviors without altering the detection of noxious stimuli, withdrawal reflexes, anxiety, or reward. Following peripheral nerve injury, innocuous stimuli activated this nociceptive ensemble to drive dysfunctional perceptual changes associated with neuropathic pain, including pain aversion to light touch (allodynia). These results identify the amygdalar representations of noxious stimuli that are functionally required for the negative affective qualities of acute and chronic pain perception.

The emotional dimension of pain

Neuroscience The unpleasantness of pain is an emotional phenomenon distinct from pain's sensory qualities. To study how the brain processes pain-related emotions, Corder et al. used in vivo neural calcium imaging in freely behaving mice. They identified brain circuits that respond to pain and directly tested their causal role in motivational behaviors associated with acute and chronic pain. Science , this issue p. [276][1] [1]: /lookup/doi/10.1126/science.aap8586

Can pictorial images communicate the quality of pain successfully?

Chronic pain is common and difficult for patients to communicate to health professionals. It may include neuropathic elements which require specialised treatment. A little used approach to communicating the quality of pain is through the use of images. This study aimed to test the ability of a set of 12 images depicting different sensory pain qualities to successfully communicate those qualities. Images were presented to 25 student nurses and 38 design students. Students were asked to write down words or phrases describing the quality of pain they felt was being communicated by each image. They were asked to provide as many or as few as occurred to them. The images were extremely heterogeneous in their ability to convey qualities of pain accurately. Only 2 of the 12 images were correctly interpreted by more than 70% of the sample. There was a significant difference between the two student groups, with nurses being significantly better at interpreting the images than the design students. Clearly, attention needs to be given not only to the content of images designed to depict the sensory qualities of pain but also to the differing audiences who may use them. Education, verbal ability, ethnicity and a multiplicity of other factors may influence the understanding and use of such images. Considerable work is needed to develop a set of images which is sufficiently culturally appropriate and effective for general use.

Mental imagery in chronic pain: Prevalence and characteristics

Research into mental imagery has increased our understanding of a range of psychological problems. However, there has been little study into the spontaneous mental images experienced in response to chronic pain. This study aimed to explore the prevalence and characteristics of these pain-related mental images. Four hundred ninety-one people with chronic pain who had attended a pain clinic were sent invites to participate and 105 people responded (21%). A mixed-methods approach (quantitative and qualitative) was used to explore the prevalence of pain-related mental imagery, differences between imagers and non-imagers, and the content of imagery in pain. In our sample, 36% of respondents reported having mental images of their pain, with the majority describing them as clear and vivid (83%), experienced daily (80.5%), and distressing (83%). Participants who experienced mental images reported higher depression scores, higher anxiety and higher pain unpleasantness. Frequency of imagery was associated with greater pain unpleasantness. Content analysis of the pain images revealed emerging themes relating to the sensory qualities of pain, anatomical representations, pain as a form of threat or attack, pain as an object, and pain as an abstract image. This study describes themes and characteristics of pain-related mental imagery and confirms that they are a frequent, vivid and distressing experience for many chronic pain sufferers. The results of this study suggest that pain-related mental imagery could provide an additional route for assessment and intervention. Further research should focus on assessment, measurement and intervention in clinical populations.

Psychometric Methods for Measuring Pain

Pain is a complex, multidimensional construct that includes a number of domains, such as pain severity, sensory qualities of pain, pain beliefs, coping strategies, and the functional impact of pain. In addition a variety of psychosocial factors, including affective state, the subjectivity of pain, and the degree to which one uses pain complaints to communicate about other psychosocial problems, strongly influence people's report of pain and disability. Thus it is important to recognize the various dimensions that contribute to the construct of pain and to consider evaluation methods that accurately provide for assessment of each of these dimensions. In some cases this would require administration of several domain-specific measures. Alternatively use of multidimensional measures is a viable option that often provides for more comprehensive evaluation. This chapter reviews a number of pain-related assessment measures, the constructs they purport to measure, and then briefly addresses issues related to normative data and symptom validity for each.

Sensory Pain Qualities in Neuropathic Pain

The qualities of chronic neuropathic pain (NeP) may be informative about the different mechanisms of pain. We previously developed a 2-factor model of NeP that described an underlying structure among sensory descriptors on the Short-Form McGill Pain Questionnaire. The goal of this study was to confirm the correlated 2-factor model of NeP. Individual descriptive scores from the Short-Form McGill Pain Questionnaire were analyzed. Confirmatory factor analysis was used to test a correlated 2-factor model. Factor 1 (stabbing pain) was characterized by high loadings on stabbing, sharp, and shooting sensory items; factor 2 (heavy pain) was characterized by high loadings on heavy, gnawing, and aching items. Results of the confirmatory factor analysis strongly supported the correlated 2-factor model. Perspective This article validates a model that describes the qualities of neuropathic pain associated with diabetic peripheral neuropathy and postherpetic neuralgia. These data suggest that specific pain qualities may be associated with pain mechanisms or may be useful for predicting treatment response.

Are both the sensory and the affective dimensions of pain encoded in the face?

The facial expression of pain plays a crucial role in pain communication and pain diagnostics. Despite its importance, it has remained unknown which dimensions of pain (sensory and/or affective) are encoded in the face. To answer this question, we used a well-established cognitive strategy (suggestions) to differentially modulate the sensory and affective dimensions of pain and investigate the effect of this manipulation on facial responses to experimental pain. Twenty-two subjects participated in the study. Their facial expressions, pain intensity, and unpleasantness ratings as well as skin conductance responses to tonic and phasic heat pain were assessed before and after suggestions directed toward increase in affective and sensory qualities of pain, respectively, were provided. Facial expressions were analyzed with the Facial Action Coding system. As expected, suggestions designed to increase the sensory dimension produced a selective increase in pain intensity ratings, whereas suggestions designed to increase pain affect produced increased unpleasantness ratings and elevated skin conductance responses. Furthermore, suggestions for either increased pain affect or pain sensation produced selective modulations in facial response patterns, with facial movements around the eyes mostly encoding sensory aspects, whereas movements of the eyebrows and of the upper lip were closely associated with the affective pain dimension. The facial expression of pain is a multidimensional response system that differentially encodes affective and sensory pain qualities. This differential encoding might have evolved to guarantee that the specific characteristics of one’s pain experience are facially communicated, thereby ensuring adequate help and support from others.

Douleurs postopératoires de repos après prothèse de hanche ou de genou : intensité, particularités sensorielles et retentissement sur le sommeil

Summary Introduction The management of acute postoperative pain poses a significant challenge in surgical specialities. Despite the prevalence and impact of acute postoperative pain, there is a paucity of published data regarding its occurrence and sensory qualities after joint replacement. Hypothesis That a proportion of patients would experience severe acute postoperative pain at rest after Total Hip Replacement (THR) and Total Knee Replacement (TKR). Materials and methods Pain was assessed preoperatively, and then five times daily for the first three postoperative days in 105 THR and TKR patients. Pain severity was assessed using a pain Visual Analogue Scale and the sensory qualities of pain were assessed using the pain descriptors from the Short-Form McGill Pain Questionnaire. Results Median acute pain scores peaked on the first postoperative day, with 58 % of TKR patients and 47 % of THR patients reporting moderate-severe pain. Preoperative pain was most frequently described as aching, stabbing and sharp, whereas acute postoperative pain was described as aching, heavy and tender. Night pain disturbed between 44–57 % of TKR patients and 21–52 % of THR patients on postoperative nights 1–3. Discussion These findings demonstrate that acute postoperative pain at rest after joint replacement, particularly TKR, is poorly managed, although it does not reach the severity of preoperative pain. Level of evidence Level IV (observational cohort study).

Acute postoperative pain at rest after hip and knee arthroplasty: Severity, sensory qualities and impact on sleep

The management of acute postoperative pain poses a significant challenge in surgical specialities. Despite the prevalence and impact of acute postoperative pain, there is a paucity of published data regarding its occurrence and sensory qualities after joint replacement. That a proportion of patients would experience severe acute postoperative pain at rest after total hip replacement (THR) and total knee replacement (TKR). Pain was assessed preoperatively, and then five times daily for the first three postoperative days in 105 THR and TKR patients. Pain severity was assessed using a pain Visual Analogue Scale and the sensory qualities of pain were assessed using the pain descriptors from the Short-Form McGill Pain Questionnaire. Median acute pain scores peaked on the first postoperative day, with 58% of TKR patients and 47% of THR patients reporting moderate-severe pain. Preoperative pain was most frequently described as aching, stabbing and sharp, whereas acute postoperative pain was described as aching, heavy and tender. Night pain disturbed between 44-57% of TKR patients and 21-52% of THR patients on postoperative nights 1-3. These findings demonstrate that acute postoperative pain at rest after joint replacement, particularly TKR, is poorly managed, although it does not reach the severity of preoperative pain. Level IV (observational cohort study).

Pain Quality Predicts Lidocaine Analgesia among Patients with Suspected Neuropathic Pain

Oral sodium channel blockers have shown mixed results in randomized controlled trials despite the known importance of sodium channels in generating pain. We hypothesized that differing baseline pain qualities (e.g. "stabbing" vs "dull") might define specific subgroups responsive to intravenous (IV) lidocaine-a potent sodium channel blocker. A prospective cohort study of 71 patient with chronic pain suspected of being neuropathic were recruited between January 2003 and July 2007 and underwent lidocaine infusions at Stanford University Hospital in a single-blind nonrandomized fashion. Baseline sensory pain qualities were measured with the Short-Form McGill Pain Questionnaire (SF-MPQ). Pain intensity was measured with a visual analog scale (VAS). Factor analysis demonstrated two underlying pain quality factors among SF-MPQ sensory items: a heavy pain and a stabbing pain. Baseline heavy pain quality, but not stabbing quality predicted subsequent relief of pain intensity in response to lidocaine. In contrast, these factors did not predict divergent analgesic responses to placebo infusions. In response to each 1 mcg/mL increase in lidocaine plasma level, patients with high heavy pain quality drop their VAS 0.24 (95% CI 0.05-0.43) more points than those with low heavy pain quality (P < 0.013). "Heavy" pain quality may indentify patients with enhanced lidocaine responsiveness. Pain quality may identify subgroups among patients with suspected neuropathic pain responsive to IV lidocaine. Further investigation is warranted to validate and extend these findings.

Response to Smith’s Letter to the Editor ‘Emotional Empathy in Autism Spectrum Conditions: Weak, Intact, or Heightened?’

Dear Editor, We read with interest the Letter by Smith (2009) suggesting that individuals with Autism Spectrum Conditions (ASC) have heightened emotional empathy (EE). We are pleased to be invited to contribute to the discussion. We do this by commenting on both the evidence cited by Smith, and also the evidence he does not cite. We conceptually reframe the question being posed and argue that, in the light of a broader review of the evidence, empathic responses in people with ASC are in general reduced. However, a basic type of empathic response that would fall into Smith’s definition of EE may indeed be heightened (a self-oriented personal distress response to others’ distress). We end by suggesting additional avenues to be explored. Empathy is a process where another person’s mental state (which include intentions, desires, emotions and proprioceptive states) automatically activates in the observer a representation of the observed state. These representations, unless inhibited, prime associated autonomic and somatic responses in the observer, thus generating a state in the observer that is more appropriate to the state of the person being observed (Baron-Cohen and Wheelwright 2004). The empathic process can therefore be considered as a superordinate category that includes many phenomena sharing this same underlying mechanism (Preston and de Waal 2002). Minio-Paluello et al. (2009) addressed the embodied side of empathy in people with ASC by investigating the response to others’ pain using a paradigm that involved watching a hand being penetrated by a needle. Facial or vocal representations of pain were not shown, to avoid any confound due to emotion recognition difficulties (Humphreys et al. 2007; Ashwin et al. 2006; Kuusikko et al. 2009) or atypical face processing (Spezio et al. 2007; Behrmann et al. 2006) in ASC. This study found that when observing another person’s physical pain, unlike controls, participants with ASC did not show a neurophysiological response as if they were experiencing pain themselves, and nor did their neurophysiological response correlate with the imagined pain sensory qualities. Instead, participants with ASC represented others’ pain in relation to the level of self-oriented arousal experienced while watching pain affecting another person. Further, participants with high empathy and a low number of autistic traits showed a stronger embodied empathy response. Thus, embodiment of another person’s state is one possible mechanism underlying the empathic process (Niedenthal 2007; Gallese 2007) and one that seems reduced in ASC (Minio-Paluello et al. 2009; Williams 2008). Reduced embodiment in people with ASC does not directly relate to their level of EE, defined by Smith (2009) as ‘an emotional response in an individual that stems from and parallels the emotional state of another individual’ (italics added). In the study by Minio-Paluello et al. (2009), for example, neither participants with ASC nor controls reported vicariously experiencing any pain while watching the model’s hand being penetrated by the needle. I. Minio-Paluello (&) Dipartimento di Psicologia La Sapienza, Universita’ di Roma, Via dei Marsi 78, 00185 Rome, Italy e-mail: ilaria.miniopaluello@uniroma1.it

Absence of Embodied Empathy During Pain Observation in Asperger Syndrome

Asperger syndrome (AS) is a neurodevelopmental condition within the autism spectrum conditions (ASC) characterized by specific difficulties in communication, social interaction, and empathy that is essential for sharing and understanding others' feelings and emotions. Although reduced empathy is considered a core feature of ASC, neurophysiological evidence of empathic deficits before and below mentalizing and perspective taking is lacking. We explored whether people with AS differ from neurotypical control participants in their empathic corticospinal response to the observation of others' pain and the modulatory role played by phenomenal experience of observed pain and personality traits. Sixteen right-handed men with AS (aged 28.0+/-7.2 years) and 20 neurotypical controls (aged 25.3+/-6.7 years) age, sex, and IQ matched, underwent single-pulse transcranial magnetic stimulation during observation of painful and nonpainful stimuli affecting another individual. When observing other's pain, participants with AS, in contrast to neurotypical control participants, did not show any amplitude reduction of motor-evoked potentials recorded from the muscle vicariously affected by pain, nor did their neurophysiological response correlate with imagined pain sensory qualities. Participants with AS represented others' pain in relation to the self-oriented arousal experienced while watching pain videos. Finding no embodiment of others' pain provides neurophysiological evidence for reduced empathic resonance in people with AS and indicates that their empathic difficulties involve not only cognitive dimensions but also sensorimotor resonance with others. We suggest that absence of embodied empathy may be linked to changes at very basic levels of neural processing.

Relation entre l’intensité de la douleur de l’accouchement et celle du postpartum blues

The aim of this study was to highlight a link between childbirth pain and mood disorders in the immediate postpartum. We met 43 women at three days postpartum in a maternity unit in Toulouse (France) between January and April 2004. The mean age of the mothers was 30 years (S.D., 4.8 years; range, 18-39 years). Mothers were excluded if they did not speak French, if they had past psychiatric history, and if their baby was premature, ill, or stillborn. Pain was measured using a French version of the McGill pain questionnaire (Melzack, 1975) [Br J Psychiatry 171 (1997) 550-555]. This questionnaire called questionnaire douleur Saint-Antoine (QDSA) is composed of 58 words and 16 classes (Boureau et at., 1984) [Thérapie 39 (1984) 119-129]. Classes 1-9 provide data on the sensory qualities of pain while Classes 10-16 reflect affective characteristics. Blues symptoms was assessed with the French version of the maternity blues questionnaire of Kennerley and Gath (1989) [Br J Psychiatry 145 (1984) 620-625]. For each 28 items women have to decide how much change there is from their usual self, by ticking one choice out of five, from "much less than usual" to "much more than usual". We used the French version of the EPDS (Cox et al., 1987) [Br J Psychiatry 150 (1987) 782-786]. This scale was used to assess the intensity of depressive mood. The results revealed a significant positive correlation between the pain scores and the "maternity blues" questionnaire scores, and between pain scores and EPDS score at three days postpartum. This study shows a stronger association between intensity of postpartum blues and affective aspect of childbirth pain (r=0.48; p<0.05) than between blues and sensorial aspect of pain (r=0.40; p<0.05). The level of depressive mood was found to be associated with affective (r=0.32; p<0.05) but not with sensory qualities of childbirth pain (r=0.28; p<0.05). In a multiple regression analysis predicting intensity of postpartum blues, we entered sensorial and affective scores of QDSA, age, and postpartum blues scores. The subjects to predictors ratio was adequate for multiple regression analysis as it was around the traditional guideline of at least ten participants per predictor [Howell DC. Statistical methods for psychology. Fourth ed. Duxbury press; 1997]. This model accounted for 31% of the variance of intensity of blues (F3,39=5.9, p=0.002). Affective dimension of pain was the only significant predictor (p=0.36, p=0.047). In another multiple regression analysis predicting intensity of depressive mood, we entered the same predictors. This model accounted for 20% of the variance of blues intensity (F3,39=3.26, p=0.03). Age was the only significant predictor (beta=-0.31, p=0.04). These results confirm our hypothesis that intensity of the childbirth pain is associated with mood disorders in the immediate postpartum. Several explications can be advanced. First, maternity blues could be a reaction to stress caused by childbirth pain. Moreover, pain can be felt as a failure for women who prepared themselves to a painless labor. Indeed, the prepared childbirth training pretends to give women the ability to overcome pain through physical and mental training. Thus, their responsibility in coping with the labor is heavy and might make them feel guilty if they fail. In addition, since "the labor itself should be experienced as a positive moment" [Chertock L. Féminité et maternité: étude clinique et expérimentale sur l'accouchement sans douleur. Paris: Desclée de Brouwer; 1996], pain might be at the origin of a great disappointment [Acta Obstet Gynecol Scand 83 (2004) 57-61]. It should be noted that we used the QDSA as a measure of past pain and not as a measure of immediate pain, as Melzack recommended [Pain 1 (1975) 277-299]. According to the results of this study, our hypothesis assuming a link between the intensity of labor pain and mood disorders in early postpartum appears to be confirmed. The intensity of postpartum blues is the best predictor of postnatal depression. Hence, knowledge of the risk factors, such as pain, could help to improve the efficiency of detection, and let professionals focus on the psychological impact of labor and especially on post-traumatic stress disorders.

Subtype-selective sodium channel blockers promise a new era of pain research

Chronic pain affects ≈1.5 million patients worldwide. Despite several treatment options, successful pain management is difficult to achieve, and this area of therapy remains a major unmet medical need. Chronic pain is thought to originate from aberrant electrical signaling in the nervous system. Pain-sensing neurons of the peripheral nervous system express several sodium channel (Nav1) subtypes. Their relative contribution to pain signaling is the subject of intense research and debate, and they may vary depending on the cause, anatomical location, and sensory qualities of pain. Knockdown of individual sodium channel subtypes in rodents, either by genetic ablation or through treatment with antisense oligonucleotides, has provided important information on this subject. However, interpretation of the results may be confounded by compensatory mechanisms, in the case of genetic ablation, or residual protein expression and inflammation associated with the oligonucleotide administration, in the case of the antisense technology. Subtype-selective pharmacological agents are needed to identify unambiguously the roles of individual Nav1 subtypes, but, despite years of efforts, such agents have been difficult to identify. The manuscript by Jarvis et al. (1) in this issue of PNAS reveals the first reputed Nav1.8-selective small-molecule sodium channel blocker to be publicly disclosed. By providing a much-sought-after exciting new tool, this work represents a …

Transcranial magnetic stimulation highlights the sensorimotor side of empathy for pain

Pain is intimately linked with action systems that are involved in observational learning and imitation. Motor responses to one's own pain allow freezing or escape reactions and ultimately survival. Here we show that similar motor responses occur as a result of observation of painful events in others. We used transcranial magnetic stimulation to record changes in corticospinal motor representations of hand muscles of individuals observing needles penetrating hands or feet of a human model or noncorporeal objects. We found a reduction in amplitude of motor-evoked potentials that was specific to the muscle that subjects observed being pricked. This inhibition correlated with the observer's subjective rating of the sensory qualities of the pain attributed to the model and with sensory, but not emotional, state or trait empathy measures. The empathic inference about the sensory qualities of others' pain and their automatic embodiment in the observer's motor system may be crucial for the social learning of reactions to pain.