The sensory and affective components of pain: are they differentially modifiable dimensions or inseparable aspects of a unitary experience? A systematic review

The sensory and affective components of pain differentially shape pupillary dilatation during cold pressor tests

Nociceptive and affective stimuli increase reflex sympathetic outflow to the pupils. To investigate effects of stimulus intensity, unpleasantness and distress on these pupillary reflexes, and to assess their stability, healthy participants immersed their hand in ice-water three times (for 20, 40 and 60 s; or 60, 40 and 20 s; or three times for 60 s) (N = 21 in each condition). Each ice-water immersion was preceded by a 90 s warm water immersion. To evaluate phasic sympathetic influences on pupil diameter, pupillary re-dilatation after 1 s of bright light was assessed during the last 10 s of each immersion. By-and-large, pain ratings and pupil diameter were greater during longer than shorter ice-water immersions, and ice-water immersions facilitated pupillary re-dilatation after the flash stimulus. However, mean pupil diameter during ice- and warm water immersions, minor ipsilateral amplification of the pupillary response, and ratings of pain unpleasantness and distress decreased across the experiment. Together, these findings suggest that nociceptive input increased sympathetic pupillary tone and amplified phasic increases in sympathetic activity after exposure to light. However, tonic sympathetic influences on pupil diameter and lateralization decreased across repeated immersions, possibly as novel or threatening aspects of the experience declined. Pupillary nociceptive and affective reflexes involve the locus coeruleus, an integral component of neural circuits that heighten cortical arousal and regulate pain. As these reflexes appear to reflect different aspects of sensory and affective processing, their combined assessment might increase the sensitivity and specificity of tests of locus coeruleus function in patients with suspected deficits.

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

ABSTRACT

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.

The intralaminar thalamus: a review of its role as a target in functional neurosurgery

The intralaminar thalamus, in particular the centromedian-parafascicular complex, forms a strategic node between ascending information from the spinal cord and brainstem and forebrain circuitry that involves the cerebral cortex and basal ganglia. A large body of evidence shows that this functionally heterogeneous region regulates information transmission in different cortical circuits, and is involved in a variety of functions, including cognition, arousal, consciousness and processing of pain signals. Not surprisingly, the intralaminar thalamus has been a target area for (radio)surgical ablation and deep brain stimulation (DBS) in different neurological and psychiatric disorders. Historically, ablation and stimulation of the intralaminar thalamus have been explored in patients with pain, epilepsy and Tourette syndrome. Moreover, DBS has been used as an experimental treatment for disorders of consciousness and a variety of movement disorders. In this review, we provide a comprehensive analysis of the underlying mechanisms of stimulation and ablation of the intralaminar nuclei, historical clinical evidence, and more recent (experimental) studies in animals and humans to define the present and future role of the intralaminar thalamus as a target in the treatment of neurological and psychiatric disorders.

Efficacy of transcranial direct current stimulation (tDCS) on pain and shoulder range of motion in post-mastectomy pain syndrome patients: a randomized-control trial

Background

Post-mastectomy pain syndrome (PMPS) is a highly prevalent complication after surgical treatment for breast cancer, and it affects the patient’s quality of life in aspects of losing shoulder full range of motion, pain, and depression. Transcranial direct current stimulation (tDCS) is non-invasive brain stimulation technique that was used in numerous clinical applications and in pain reduction in cancer patients. However, the effectiveness of tDCS on PMPS has never been evaluated in an experimental study.

Aim

To investigate the effect of bilateral anodal tDCS of motor cortex (M1) on pain, depression, and shoulder range of motion (ROM) in post-mastectomy pain syndrome.

Study design

Randomized controlled trial.

Methods

A total of 30 female patients with post-mastectomy neuropathic pain were randomized into two groups; the intervention group which received bilateral tDCS on motor cortex (M1) and the control group that received sham bilateral tDCS on M1. As pain affects shoulder range of motion (ROM), shoulder ROM was measured by electronic goniometer pre- and post-tDCS application. In addition, the levels of pain and depression have been measured pre and post treatment. Pain has been measured with visual analogue scale (VAS) and depression with Beck-Depression-Inventory-BDI questionnaire (BDI).

Results

A significant difference was noted in group A regarding pain, depression and shoulder ROM (p= 0.001, p= 0.003, and p= 0.003, respectively). Between group comparison revealed a significant difference of VAS scores and shoulder flexion ROM between groups, the study group and the control group (p=0.041 and 0.048, respectively). Pain decreased by 32% and Shoulder flexion increased by 4.8% post-treatment while there were no significant difference in group B (p=0.567 and p=0.866, respectively).

Conclusions

The application of tDCS decreases the severity of pain and improves shoulder range of motion suffered by breast cancer patients after total mastectomy surgery.

Relationship between the affective dimension of pain and site of the disorder: A cross-sectional study

BACKGROUND

Pain is a complex experience with both sensory and affective dimensions, and the affective dimension can increase the risks of chronic pain development. It is thus critical to identify factors influencing the affective dimension of pain.

OBJECTIVE

This study aimed to identify the relationship between the affective dimension of pain and disorder site (primary pain source).

METHODS

Study participants were recruited from patients referred for physical therapy at an orthopedic outpatient clinic. Pain quality including the affective dimension, disorder site from descriptive medical diagnosis, pain intensity, duration from pain onset, and demographic data, was collected. A multivariable logistic regression model was constructed to analyze the relationship between the affective dimension of pain and the disorder site.

RESULTS

A total of 282 participants were included. Cervical and lumbar spine disorders were significantly associated with an affective dimension of pain compared to limbs disorders when adjusted for age, sex, pain intensity, and duration from the onset in the regression model.

CONCLUSIONS

Regardless of duration from the onset and other confounding factors, disorder site is correlated with the affective dimension of pain. Multidimensional pain assessment is crucial when clinicians evaluate patients with cervical and lumbar spine disorders, even in the acute phase.

The Effect of Observing High or Low Pain on the Development of Central Sensitization

It is unknown whether watching other people in high pain increases mechanical hypersensitivity induced by pain. We applied high-frequency electrical stimulation (HFS) on the skin of healthy volunteers to induce pinprick mechanical hypersensitivity. Before HFS participants were randomly allocated to 2 groups: in the low pain group, which was the control condition, they watched a model expressing and reporting lower pain scores, in the high pain group the model expressed and reported higher scores. The 2 videos were selected on the basis of a pilot/observational study that had been conducted before. We tested the differences in perceived intensity of the HFS procedure, in the development of hypersensitivity and the role of fear and empathy. The high pain group reported on average higher pain ratings during HFS. The perceived intensity of hypersensitivity, but not the unpleasantness or the length of the area was higher in the high pain group. Our results suggest that watching a person expressing more pain during HFS increases one's own pain ratings during HFS and may weakly facilitate the development of secondary mechanical hypersensitivity, although this latter result needs replication. PERSPECTIVE: Observing a person in high pain can influence the perceived pain intensity of a procedure leading to secondary mechanical hypersensitivity, and has a weak effect on hypersensitivity itself. The role of fear remains to be elucidated.

Efficacy of Conservative Therapy in Overhead Athletes with Glenohumeral Internal Rotation Deficit: A Systematic Review and Meta-Analysis

BACKGROUND

To evaluate the effectiveness of conservative therapy in range of movement (ROM), strength, pain, subacromial space and physical function, in overhead athletes with glenohumeral internal rotation deficit (GIRD).

METHODS

A systematic review and meta-analysis was designed, and the protocol was registered in PROSPERO (CRD42021281559). The databases searched were: PubMed, Cochrane Central Register of Controlled Trials, Physiotherapy Evidence Database, Web of Science and SCOPUS. Randomized controlled trials (RCTs) involving conservative therapy applied in overhead athletes with GIRD were included. Two independent assessors evaluated the quality of the studies with the PEDro scale, and with the Cochrane Risk-of-Bias tool. The overall quality of the evidence was assessed using GRADE. Data on outcomes of interest were extracted by a researcher using RevMan 5.4 software. Estimates were presented as standardized mean differences (SMD) with 95% confidence intervals (CIs).

RESULTS

A total of eleven studies involving 514 overhead athletes were included in the systematic review; of these 8 were included in the meta-analysis. The methodological quality of the included RCTs ranged from high to low. Conservative therapy showed significant improvements in internal rotation, adduction, physical function and subacromial space.

CONCLUSIONS

Conservative therapy based on stretch, passive joint and muscular mobilizations can be useful to improve the internal rotation and adduction ROM, subacromial space, and physical function of the shoulder in overhead athletes with glenohumeral internal rotation deficit.

Influence of Skin Phototype on the Level of Pain Perceived by Patients Receiving Enoxaparin: A Cross-Sectional Study

Low Molecular Weight Heparin (LMWH) is commonly used as an antithrombotic in patients with reduced mobility. Its administration is performed by invasive technique (injections) that can cause pain: (1) Background: Pain and bruising are the most common side effects in patients treated with LMWH, but the skin phototype (PT) has never been included; (2) Methods: A cross-sectional descriptive study, developed in the Hospital Unit of Orthopedic and Trauma Surgery over one year. To classify all participants in the sample considering their skin PT and the different pain levels "during" and "after" the administration of enoxaparin. The STROBE checklist was used to evaluate the study. Data analyses were carried out: descriptive statistical analysis and analysis of Variance ANOVA of a non-parametric factor; (3) Results: The sample was 202 participants. The most frequent skin PTs were PT II 43.6% and PT III 33.2%. Mean pain after injection (1.96) was greater than pain during injection (1.4). Better natural protection against sunlight (high PT) would indicate greater post-injection pain; (4) Conclusions: Participants with a medium-high phototype (≥III) perceive a greater pain sensation than participants with a low phototype (≤II) after the administration of enoxaparin.

Clinical efficacy of electromagnetic field therapy combined with traditional Chinese pain-reducing paste in myofascial pain syndrome

BACKGROUND

Pulsed electromagnetic field (PEMF) therapy is widely used to treat myofascial pain syndrome (MPS). Damp-clearing and pain-reducing paste (DPP) comprises medical herbs and has been a traditional method of reducing myofascial pain in China for a long time, and it is usually administered with heating. However, the synergistic effect of PEMF therapy on heating-DPP in patients with MPS is unclear.

AIM

To investigate the synergistic effect of PEMF therapy plus heating-DPP in lumbar MPS.

METHODS

This double-blind, randomized, placebo-controlled trial was conducted on 120 patients with lumbar MPS who were randomly divided into an experimental group (EG, n = 60) and a control group (CG, n = 60). Patients in both groups were treated with heating-DPP combined with PEMF therapy; however, the electromagnetic function of the therapeutic apparatus used in the CG was disabled. Each treatment lasted for 20 min and was applied five times a week for two weeks. The short-form McGill Pain Questionnaire was applied at five time points: pretest, end of the first and second weeks of treatment, and end of the first and fourth week after completing treatment. Visual analog scale (VAS), present pain intensity index (PPI), and pain rating index (PRI; total, affective pain, and sensory pain scores) scores were then analyzed.

RESULTS

Compared with the CG, the VAS, PPI and PRI scores (total, affective pain and sensory pain scores) in the EG were significantly lower after treatment and during follow-up.

CONCLUSION

PEMF therapy combined with heating-DPP showed better efficacy than heating-DPP alone in reducing the overall intensity of pain and sensory and affective pain.

Translating Outcomes from the Clinical Setting to Preclinical Models: Chronic Pain and Functionality in Chronic Musculoskeletal Pain

Fibromyalgia (FM) is a chronic pain disorder characterized by chronic widespread musculoskeletal pain (CWP), resting pain, movement-evoked pain (MEP), and other somatic symptoms that interfere with daily functioning and quality of life. In clinical studies, this symptomology is assessed, while preclinical models of CWP are limited to nociceptive assays. The aim of the study was to investigate the human-to-model translatability of clinical behavioral assessments for spontaneous (or resting) pain and MEP in a preclinical model of CWP. For preclinical measures, the acidic saline model of FM was used to induce widespread muscle pain in adult female mice. Two intramuscular injections of acidic or neutral pH saline were administered following baseline measures, 5 days apart. An array of adapted evoked and spontaneous pain measures and functional assays were assessed for 3 weeks. A novel paradigm for MEP assessment showed increased spontaneous pain following activity. For clinical measures, resting and movement-evoked pain and function were assessed in adult women with FM. Moreover, we assessed correlations between the preclinical model of CWP and in women with fibromyalgia to examine whether similar relationships between pain assays that comprise resting and MEP existed in both settings. For both preclinical and clinical outcomes, MEP was significantly associated with mechanical pain sensitivity. Preclinically, it is imperative to expand how the field assesses spontaneous pain and MEP when studying multi-symptom disorders like FM. Targeted pain assessments to match those performed clinically is an important aspect of improving preclinical to clinical translatability of animal models.

The neurobiology of pain and facial movements in rodents: Clinical applications and current research

One of the most controversial aspects of the use of animals in science is the production of pain. Pain is a central ethical concern. The activation of neural pathways involved in the pain response has physiological, endocrine, and behavioral consequences, that can affect both the health and welfare of the animals, as well as the validity of research. The strategy to prevent these consequences requires understanding of the nociception process, pain itself, and how assessment can be performed using validated, non-invasive methods. The study of facial expressions related to pain has undergone considerable study with the finding that certain movements of the facial muscles (called facial action units) are associated with the presence and intensity of pain. This review, focused on rodents, discusses the neurobiology of facial expressions, clinical applications, and current research designed to better understand pain and the nociceptive pathway as a strategy for implementing refinement in biomedical research.

Skills or Pills: Randomized Trial Comparing Hypnotherapy to Medical Treatment in Children With Functional Nausea

BACKGROUND & AIMS

The potential effectiveness of gut-directed hypnotherapy (HT) is unknown for pediatric chronic nausea. This randomized controlled trial compared HT with standard medical treatment (SMT).

METHODS

One hundred children (ages, 8-18 y) with chronic nausea and fulfilling functional nausea (FN) or functional dyspepsia (FD) criteria were allocated randomly (1:1) to HT or SMT, with a 3-month intervention period. Outcomes were assessed at baseline, at the halfway point, after treatment, and at the 6- and 12-month follow-up evaluation. Children scored nausea symptoms in a 7-day diary. The primary outcome was treatment success, defined as a reduction in nausea of 50% or more, at the 12-month follow-up evaluation. Secondary outcomes included adequate relief of nausea.

RESULTS

After treatment and at the 6-month follow-up evaluation, there was a trend toward higher treatment success in the HT group compared with the SMT group (45% vs 26%, P = .052; and 57% vs 40%, P = .099, respectively). At 12 months, treatment success was similar in both groups (60% in the HT group and 55% in the SMT group; P = .667). In the FN group, significantly higher success rates were found for HT, but no differences were found in patients with FD. Adequate relief was significantly higher in the HT group than in the SMT group at the 6-month follow-up evaluation (children: 81% vs 55%, P = .014; parents: 79% vs 53%; P = .016), but not at the 12-month follow-up evaluation.

CONCLUSIONS

HT and SMT were effective in reducing nausea symptoms in children with FN and FD. In children with FN, HT was more effective than SMT during and after the first 6 months of treatment. Therefore, HT and SMT, applied separately or in combination, should be offered to children with FN as a treatment option (Clinical trials registration number: NTR5814).

A systematic literature review and narrative synthesis on the risk factors for developing affective disorders in open lower-limb fracture patients

Background

Despite the advancements made in the management of the physical complications of open lower-limb fractures, few studies have been performed which investigate the association of such injuries with affective disorders. The complications resulting from this injury may result in significant psychological distress.

Aim

To evaluate the risk factors associated with the development of affective disorders, in patients with open lower-limb fractures.

Methods

A systematic review protocol was registered with PROSPERO and reported in accordance with the Preferred Reporting for Items for Systematic Reviews and Meta-Analyses. A comprehensive literature search was performed to gather relevant papers. Two independent reviewers screened titles and abstracts according to the inclusion and exclusion criteria.

Results

2488 were screened according to the inclusion and exclusion criteria resulting in seven articles eligible for inclusion. Of the seven articles, two assessed for PTSD, one assessed for depression and PTSD concurrently, two assessed for anxiety and depression concurrently, and two assessed for psychological distress. With the exception of two studies, open lower limb fracture patients were included with other lower-limb injuries in their analysis. Furthermore, not all variables were available in all included studies. Risk factors identified included post-operative pain, mechanism and severity of injury, age of patient, social support and social deprivation.

Conclusions

Further studies are required within this area. However, addressing risk factors such as pain management, poor social support and inappropriate coping mechanisms, may reduce the incidence of affective disorders by equipping patients with necessary psychosocial resources.

•

Patients with strong social support have, in general, a lower risk of depression and psychological distress.

•

Poverty is a risk factor in general for psychological distress.

•

Negative affect may play an important role in determining physical function during the recovery period.

•

In most patients, symptoms of psychological distress improve over time.

•

Not all patients may display symptoms of psychological distress immediately post-injury.

A Dysfunctional Descending Pain Modulation System in Chronic Nonspecific Low Back Pain: A Systematic Review and ALE Meta-Analysis

Pain, a physiological protective mechanism, turns into a complex dynamic neural response when it becomes chronic. The role of neuroplastic brain changes is more evident than the peripheral factors in the maintenance, modulation and amplification of chronic low back pain (cLBP). In this background, we summarise the brain changes in cLBP in a coordinate-based activation likelihood estimation (ALE) meta-analysis of previous functional magnetic resonance imaging (fMRI) studies. Databases ('PubMed', 'Scopus' and 'Sleuth') were searched till May 2022 and the activity pattern was noted under the 'without stimulation' and 'with stimulation' groups. A total of 312 studies were selected after removing duplicates. Seventeen (553 cLBP patients, 192 activation foci) studies were fulfilled the eligibility criteria and included in the 'without stimulation' group. Twelve statistically significant clusters are localized in the prefrontal cortex, primary somatosensory cortex, primary motor cortex, parietal cortex, anterior cingulate cortex, caudate, putamen, globus pallidus amygdala, occipital lobe, temporal lobe and associated white matter in this group. Ten studies (353 cLBP patients, 125 activation foci) were selected in the' with stimulation' groups. In this group, seven statistically significant clusters were found in the frontal cortex, orbitofrontal cortex, premotor cortex, parietal cortex, claustrum and insula. These statistically significant clusters indicate a probable imbalance in GABAergic modulation of brain circuits and dysfunction in the descending pain modulation system. This disparity in the pain neuro-matrix is the source of spontaneous and persisting pain in cLBP.

The Promise of Behavioral Tracking Systems for Advancing Primate Animal Welfare

Recent years have witnessed major advances in the ability of computerized systems to track the positions of animals as they move through large and unconstrained environments. These systems have so far been a great boon in the fields of primatology, psychology, neuroscience, and biomedicine. Here, we discuss the promise of these technologies for animal welfare. Their potential benefits include identifying and reducing pain, suffering, and distress in captive populations, improving laboratory animal welfare within the context of the three Rs of animal research (reduction, refinement, and replacement), and applying our understanding of animal behavior to increase the "natural" behaviors in captive and wild populations facing human impact challenges. We note that these benefits are often incidental to the designed purpose of these tracking systems, a reflection of the fact that animal welfare is not inimical to research progress, but instead, that the aligned interests between basic research and welfare hold great promise for improvements to animal well-being.

The Affective Dimension of Pain Appears to Be Determinant within a Pain-Insomnia-Anxiety Pathological Loop in Fibromyalgia: A Case-Control Study

Background: Fibromyalgia (FM) is a chronic pain disease characterized by multiple symptoms whose interactions and implications in the disease pathology are still unclear. This study aimed at investigating how pain, sleep, and mood disorders influence each other in FM, while discriminating between the sensory and affective pain dimensions. Methods: Sixteen female FM patients were evaluated regarding their pain, while they underwent—along with 11 healthy sex- and age-adjusted controls—assessment of mood and sleep disorders. Analysis of variance and correlations were performed in order to assess group differences and investigate the interactions between pain, mood, and sleep descriptors. Results: FM patients reported the typical widespread pain, with similar sensory and affective inputs. Contrary to controls, they displayed moderate anxiety, depression, and insomnia. Affective pain (but neither the sensory pain nor pain intensity) was the only pain indicator that tendentially correlated with anxiety and insomnia, which were mutually associated. An affective pain–insomnia–anxiety loop was thus completed. High ongoing pain strengthened this vicious circle, to which it included depression and sensory pain. Conclusions: Discriminating between the sensory and affective pain components in FM patients disclosed a pathological loop, with a key role of affective pain; high ongoing pain acted as an amplifier of symptoms interaction. This unraveled the interplay between three of most cardinal FM symptoms; these results contribute to better understand FM determinants and pathology and could help in orienting therapeutic strategies.

Does art reduce pain and stress? A registered report protocol of investigating autonomic and endocrine markers of music, visual art, and multimodal aesthetic experience

The pain- and stress-reducing effects of music are well-known, but the effects of visual art, and the combination of these two, are much less investigated. We aim to (1) investigate the pain- and (2) stress-reducing effects of multimodal (music + visual art) aesthetic experience as we expect this to have stronger effects than a single modal aesthetic experience (music/ visual art), and in an exploratory manner, (3) investigate the underlying mechanisms of aesthetic experience, and the (4) individual differences. In a repeated-measures design (music, visual art, multimodal aesthetic experience, control) participants bring self-selected “movingly beautiful” visual artworks and pieces of music to the lab, where pain and stress are induced by the cold pressor test. Activity of the pain and stress responsive systems are measured by subjective reports, autonomic (electrocardiography, electrodermal activity, salivary alpha-amylase) and endocrine markers (salivary cortisol).

Gamma Band Oscillations Reflect Sensory and Affective Dimensions of Pain

Pain is a multidimensional process, which can be modulated by emotions; however, the mechanisms underlying this modulation are unknown. We used pictures with different emotional valence (negative, positive, and neutral) as primes and applied electrical painful stimuli as targets to healthy participants. We assessed pain intensity and unpleasantness ratings and recorded electroencephalograms (EEGs). We found that pain unpleasantness and not pain intensity ratings were modulated by emotion, with increased ratings for negative and decreased ratings for positive pictures. We also found two consecutive gamma band oscillations (GBOs) related to pain processing from time frequency analyses of the EEG signals. The early GBO had a cortical distribution contralateral to the painful stimulus and its amplitude was positively correlated with intensity and unpleasantness ratings, but not with prime valence. The late GBO had a centroparietal distribution and its amplitude was larger for negative compared to neutral and positive pictures. The emotional modulation effect (negative vs. positive) of the late GBO amplitude was positively correlated with pain unpleasantness. The early GBO might reflect the overall pain perception, possibly involving the thalamocortical circuit, while the late GBO might be related to the affective dimension of pain and top-down-related processes.

Multi-Region Local Field Potential Signatures in Response to the Formalin-induced Inflammatory Stimulus in Male Rats

Pain can be ignited by noxious chemical (e.g., acid), mechanical (e.g., pressure), and thermal (e.g., heat) stimuli and generated by the activation of sensory neurons and their axonal terminals called nociceptors in the periphery. Nociceptive information transmitted from the periphery is projected to the central nervous system (thalamus, somatosensory cortex, insular, anterior cingulate cortex, amygdala, periaqueductal grey, prefrontal cortex, etc.) to generate a unified experience of pain. Local field potential (LFP) recording is one of the neurophysiological tools to investigate the combined neuronal activity, ranging from several hundred micrometers to a few millimeters (radius), located around the embedded electrode. The advantage of recording LFP is that it provides stable simultaneous activities in various brain regions in response to external stimuli. In this study, differential LFP activities from the contralateral anterior cingulate cortex (ACC), ventral tegmental area (VTA), and bilateral amygdala in response to peripheral noxious formalin injection were recorded in anesthetized male rats. The results indicated increased power of delta, theta, alpha, beta, and gamma bands in the ACC and amygdala but no change of gamma-band in the right amygdala. Within the VTA, intensities of the delta, theta, and beta bands were only enhanced significantly after formalin injection. It was found that the connectivity (i.t. the coherence) among these brain regions reduced significantly under the formalin-induced nociception, which suggests a significant interruption within the brain. With further study, it will sort out the key combination of structures that will serve as the signature for pain state.

A neuropsychosocial signature predicts longitudinal symptom changes in women with irritable bowel syndrome

Irritable bowel syndrome (IBS) is a common disorder of brain-gut interactions characterized by chronic abdominal pain, altered bowel movements, often accompanied by somatic and psychiatric comorbidities. We aimed to test the hypothesis that a baseline phenotype composed of multi-modal neuroimaging and clinical features predicts clinical improvement on the IBS Symptom Severity Scale (IBS-SSS) at 3 and 12 months without any targeted intervention. Female participants (N = 60) were identified as "improvers" (50-point decrease on IBS-SSS from baseline) or "non-improvers." Data integration analysis using latent components (DIABLO) was applied to a training and test dataset to determine whether a limited number of sets of multiple correlated baseline'omics data types, including brain morphometry, anatomical connectivity, resting-state functional connectivity, and clinical features could accurately predict improver status. The derived predictive models predicted improvement status at 3-months and 12-months with 91% and 83% accuracy, respectively. Across both time points, non-improvers were classified as having greater correlated morphometry, anatomical connectivity and resting-state functional connectivity characteristics within salience and sensorimotor networks associated with greater pain unpleasantness, but lower default mode network integrity and connectivity. This suggests that non-improvers have a greater engagement of attentional systems to perseverate on painful visceral stimuli, predicting IBS exacerbation. The ability of baseline multimodal brain-clinical signatures to predict symptom trajectories may have implications in guiding integrative treatment in the age of precision medicine, such as treatments targeted at changing attentional systems such as mindfulness or cognitive behavioral therapy.

Inhibiting spinal secretory phospholipase A2 after painful nerve root injury attenuates established pain and spinal neuronal hyperexcitability by altering spinal glutamatergic signaling

Neuropathic injury is accompanied by chronic inflammation contributing to the onset and maintenance of pain after an initial insult. In addition to their roles in promoting immune cell activation, inflammatory mediators like secretory phospholipase A₂ (sPLA₂) modulate nociceptive and excitatory neuronal signaling during the initiation of pain through hydrolytic activity. Despite having a known role in glial activation and cytokine release, it is unknown if sPLA₂ contributes to the maintenance of painful neuropathy and spinal hyperexcitability later after neural injury. Using a well-established model of painful nerve root compression, this study investigated if inhibiting spinal sPLA₂ 7 days after painful injury modulates the behavioral sensitivity and/or spinal dorsal horn excitability that is typically evident. The effects of sPLA₂ inhibition on altered spinal glutamatergic signaling was also probed by measuring spinal intracellular glutamate levels and spinal glutamate transporter (GLAST and GLT1) and receptor (mGluR5, GluR1, and NR1) expression. Spinal sPLA₂ inhibition at day 7 abolishes behavioral sensitivity, reduces both evoked and spontaneous neuronal firing in the spinal cord, and restores the distribution of neuronal phenotypes to those of control conditions. Inhibiting spinal sPLA₂ also increases intracellular glutamate concentrations and restores spinal expression of GLAST, GLT1, mGluR5, and GluR1 to uninjured expression with no effect on NR1. These findings establish a role for spinal sPLA₂ in maintaining pain and central sensitization after neural injury and suggest this may be via exacerbating glutamate excitotoxicity in the spinal cord.

Brain Mechanisms of Virtual Reality Breathing Versus Traditional Mindful Breathing in Pain Modulation: Observational Functional Near-infrared Spectroscopy Study

BACKGROUND

Pain is a complex experience that involves sensory-discriminative and cognitive-emotional neuronal processes. It has long been known across cultures that pain can be relieved by mindful breathing (MB). There is a common assumption that MB exerts its analgesic effect through interoception. Interoception refers to consciously refocusing the mind's attention to the physical sensation of internal organ function.

OBJECTIVE

In this study, we dissect the cortical analgesic processes by imaging the brains of healthy subjects exposed to traditional MB (TMB) and compare them with another group for which we augmented MB to an outside sensory experience via virtual reality breathing (VRB).

METHODS

The VRB protocol involved in-house-developed virtual reality 3D lungs that synchronized with the participants' breathing cycles in real time, providing them with an immersive visual-auditory exteroception of their breathing.

RESULTS

We found that both breathing interventions led to a significant increase in pain thresholds after week-long practices, as measured by a thermal quantitative sensory test. However, the underlying analgesic brain mechanisms were opposite, as revealed by functional near-infrared spectroscopy data. In the TMB practice, the anterior prefrontal cortex uniquely modulated the premotor cortex. This increased its functional connection with the primary somatosensory cortex (S1), thereby facilitating the S1-based sensory-interoceptive processing of breathing but inhibiting its other role in sensory-discriminative pain processing. In contrast, virtual reality induced an immersive 3D exteroception with augmented visual-auditory cortical activations, which diminished the functional connection with the S1 and consequently weakened the pain processing function of the S1.

CONCLUSIONS

In summary, our study suggested two analgesic neuromechanisms of VRB and TMB practices-exteroception and interoception-that distinctively modulated the S1 processing of the ascending noxious inputs. This is in line with the concept of dualism (Yin and Yang).

Supraspinal nociceptive networks in neuropathic pain after spinal cord injury

Neuropathic pain following spinal cord injury involves plastic changes along the whole neuroaxis. Current neuroimaging studies have identified grey matter volume (GMV) and resting-state functional connectivity changes of pain processing regions related to neuropathic pain intensity in spinal cord injury subjects. However, the relationship between the underlying neural processes and pain extent, a complementary characteristic of neuropathic pain, is unknown. We therefore aimed to reveal the neural markers of widespread neuropathic pain in spinal cord injury subjects and hypothesized that those with greater pain extent will show higher GMV and stronger connectivity within pain related regions. Thus, 29 chronic paraplegic subjects and 25 healthy controls underwent clinical and electrophysiological examinations combined with neuroimaging. Paraplegics were demarcated based on neuropathic pain and were thoroughly matched demographically. Our findings indicate that (a) spinal cord injury subjects with neuropathic pain display stronger connectivity between prefrontal cortices and regions involved with sensory integration and multimodal processing, (b) greater neuropathic pain extent, is associated with stronger connectivity between the posterior insular cortex and thalamic sub-regions which partake in the lateral pain system and (c) greater intensity of neuropathic pain is related to stronger connectivity of regions involved with multimodal integration and the affective-motivational component of pain. Overall, this study provides neuroimaging evidence that the pain phenotype of spinal cord injury subjects is related to the underlying function of their resting brain.

Role of sex hormones in modulating breast and ovarian cancer associated pain

According to the National Cancer Institute in 2020 there will be an estimated 21,750 new ovarian cancer cases and 276,480 new breast cancer cases. Both breast and ovarian cancer are hormone dependent cancers, meaning they cannot grow without the presence of hormones. The two most studied hormones in these two cancers are estrogen and progesterone, which are also involved in the modulation of pain. The incidence of pain in breast and ovarian cancer is very high. Research about mechanisms involved in modulation of pain by hormones are still being debated, as some studies find estrogen to be anti-nociceptive and others pro-nociceptive in pain studies. Moreover, analgesic treatments for breast and ovarian cancer-associated pain are limited and often ineffective. In this review, we will focus on estrogen and progesterone mechanisms of action in modulation of pain and cancer. We will also discuss new treatment options for these types of cancer and associated-pain.

Sensory Neurons, Neuroimmunity, and Pain Modulation by Sex Hormones

The inclusion of women in preclinical pain studies has become more commonplace in the last decade as the National Institutes of Health (NIH) released its "Sex as a Biological Variable" mandate. Presumably, basic researchers have not had a comprehensive understanding about neuroimmune interactions in half of the population and how hormones play a role in this. To date, we have learned that sex hormones contribute to sexual differentiation of the nervous system and sex differences in behavior throughout the lifespan; however, the cycling of sex hormones does not always explain these differences. Here, we highlight recent advances in our understanding of sex differences and how hormones and immune interactions influence sensory neuron activity to contribute to physiology and pain. Neuroimmune mechanisms may be mediated by different cell types in each sex, as the actions of immune cells are sexually dimorphic. Unfortunately, the majority of studies assessing neuronal contributions to immune function have been limited to males, so it is unclear if the mechanisms are similar in females. Finally, pathways that control cellular metabolism, like nuclear receptors, have been shown to play a regulatory role both in pain and inflammation. Overall, communication between the neuroimmune and endocrine systems modulate pain signaling in a sex-dependent manner, but more research is needed to reveal nuances of these mechanisms.

Effects of Acute Beta-Alanine Ingestion and Immersion-Plus-Exercise on Connectedness to Nature and Perceived Pain

This double-blinded, placebo-controlled, crossover study examined the effect of induced painful sensation (via acute Beta Alanine (B-ALA) ingestion) on Love and Care of Nature (LCN), heart rate (HR), rating of perceived exertion (RPE), and McGill Pain Questionnaire (MPQ) during outdoor exercise. Twenty participants volunteered on consecutive days to complete a 0.8 km (0.5 mi) up-hill hike after consuming either B-ALA (6.4 g) or placebo. Immediately after consumption participants answered LCN, RPE, and MPQ questionnaires, immersed in a natural environment for 45 min, and then completed a hike as quickly as possible without running. No difference in HR (p = 0.846), or RPE (p = 0.606) were observed between treatments. Total MPQ scores increased with consumption of B-ALA (p = 0.001). An increased LCN score was observed following exercise regardless of condition (p = 0.035). The results demonstrate that acute B-ALA supplementation is effective in increasing perceived pain sensations. The results also demonstrate an increase in LCN in the presence of increased perceptions of pain sensations during exercise.

Age as an Independent Predictor of Adult Spinal Cord Stimulation Pain Outcomes

INTRODUCTION

Spinal cord stimulation (SCS) is an efficacious chronic pain treatment most commonly used in middle-aged patients. Results from previous studies that investigated SCS' effects in older patient populations have been equivocal. We examine whether SCS outcomes correlate with age.

METHODS

We retrospectively examined prospectively collected outcomes from 189 patients who underwent SCS at Albany Medical Center between 2012 and 2020. The patients completed the Numerical Rating Scale (NRS), McGill Pain Questionnaire (MPQ), Oswestry Disability Index (ODI), Beck Depression Inventory (BDI), and Pain Catastrophizing Scale (PCS) preoperatively and 1 year postoperatively. The mean percent change in each outcome was determined and compared via a regression analysis to determine relationships between patient age and each respective outcome metrics. Demographics were compared between patients aged under 65 versus those aged 65 and older via χ2 tests.

RESULTS

All subjects demonstrated the expected improvement on NRS, BDI, PCS, and MPQ from baseline to 1-year follow-up, with several demonstrating statistically significant changes: NRS-worst pain (18.66%, p < 0.001), NRS-least pain (26.9%, p < 0.001), NRS-average pain (26.9%, p < 0.01), NRS-current pain (26.4%, p < 0.001), ODI (19.6%, p < 0.001), PCS (29.8%, p < 0.001), and MPQ (29.4%, p < 0.001). There was no significant difference between patients aged under 65 versus those aged 65 and older based on lead type (p = 0.454). Six patients (3.1%) had lead migration, one of whom was 65 or older. Regression analysis revealed improvements in MPQ-sensory and MPQ-affective scores as age increased (p < 0.001, R2 = 0.09; p = 0.046, R2 = 0.05, respectively). Age did not correlate with NRS, ODI, BDI, or PCS. Diagnosis, spinal level of SCS, and lead type were not found to influence any respective outcome measure based on covariate analysis.

CONCLUSION

This study represents the largest study where age was correlated to specific pain, depression, and disability outcomes following SCS. We provide evidence that SCS outcomes are equivalent, or better, in older patients following SCS. Based on these findings, SCS is a viable option for treatment of chronic pain in elderly patient populations.

Pain and Depression Symptoms During the Third Trimester of Pregnancy

PURPOSE

To assess the association between depression symptoms and pain characteristics, including pain intensity, location, and effectiveness of pain management strategies, among women in their third trimester of pregnancy.

DESIGN

Descriptive, exploratory cross-sectional study.

SETTING

Mobile health pregnancy application (app).

PARTICIPANTS

A convenience sample of women in their third trimester of pregnancy from across the United States.

METHODS

Women completed demographic questionnaires, the Brief Pain Inventory, and Edinburgh Postnatal Depression Scale (EPDS) through an online Web site.

RESULTS

N = 132 women participated. The sample was demographically diverse. . Women ranged in age from 18 to 39 years (M 28.1 ± SD 5.2). Most women were Caucasian (68%), with smaller percentages of Hispanic (12%) and African American (11%) women. Most had commercial insurance (59%) and a partner (85%). Of the 132 women, 79.6% reported moderate-to-severe pain. Approximately 93% experienced back and pelvic pain, whereas 27% experienced moderate-to-severe depression symptoms. Bivariate and linear regression analyses revealed that higher EPDS depression scores were associated with higher levels of pain (p < .01). Other variables significantly associated with higher EPDS scores were White race (p = .04), marital status (p = .05), and headache (p < .01).

CLINICAL IMPLICATIONS

In the third trimester of pregnancy, pain affects more than two-thirds of women and may occur with and without depression symptoms. Although the value of universal depression screening during pregnancy is widely recognized, our findings suggest clinical outcomes for pregnant women would improve with a standardized, multidimensional screen for both pain and depression symptoms. Nurses are ideally positioned to assess and advocate for the combined treatment of pain and depression.

Neuromodulation for chronic pain

Neuromodulation is an expanding area of pain medicine that incorporates an array of non-invasive, minimally invasive, and surgical electrical therapies. In this Series paper, we focus on spinal cord stimulation (SCS) therapies discussed within the framework of other invasive, minimally invasive, and non-invasive neuromodulation therapies. These therapies include deep brain and motor cortex stimulation, peripheral nerve stimulation, and the non-invasive treatments of repetitive transcranial magnetic stimulation, transcranial direct current stimulation, and transcutaneous electrical nerve stimulation. SCS methods with electrical variables that differ from traditional SCS have been approved. Although methods devoid of paraesthesias (eg, high frequency) should theoretically allow for placebo-controlled trials, few have been done. There is low-to-moderate quality evidence that SCS is superior to reoperation or conventional medical management for failed back surgery syndrome, and conflicting evidence as to the superiority of traditional SCS over sham stimulation or between different SCS modalities. Peripheral nerve stimulation technologies have also undergone rapid development and become less invasive, including many that are placed percutaneously. There is low-to-moderate quality evidence that peripheral nerve stimulation is effective for neuropathic pain in an extremity, low quality evidence that it is effective for back pain with or without leg pain, and conflicting evidence that it can prevent migraines. In the USA and many areas in Europe, deep brain and motor cortex stimulation are not approved for chronic pain, but are used off-label for refractory cases. Overall, there is mixed evidence supporting brain stimulation, with most sham-controlled trials yielding negative findings. Regarding non-invasive modalities, there is moderate quality evidence that repetitive transcranial magnetic stimulation does not provide meaningful benefit for chronic pain in general, but conflicting evidence regarding pain relief for neuropathic pain and headaches. For transcranial direct current stimulation, there is low-quality evidence supporting its benefit for chronic pain, but conflicting evidence regarding a small treatment effect for neuropathic pain and headaches. For transcutaneous electrical nerve stimulation, there is low-quality evidence that it is superior to sham or no treatment for neuropathic pain, but conflicting evidence for non-neuropathic pain. Future research should focus on better evaluating the short-term and long-term effectiveness of all neuromodulation modalities and whether they decrease health-care use, and on refining selection criteria and treatment variables.

Understanding pain perception through genetic painlessness diseases: The role of NGF and proNGF

Nerve growth factor (NGF), by binding to TrkA and p75^NTR receptors, regulates the survival and differentiation of sensory neurons during development and mediates pain transmission and perception during adulthood, by acting at different levels of the nervous system. Key to understanding the role of NGF as a pain mediator is the finding that mutations (namely, R121W, V232fs and R221W) in the NGF gene cause painlessness disease Hereditary Sensory and Autonomic Neuropathy type V (HSAN V). Here we shall review the consequences of these NGF mutations, each of which results in specific clinical signs: R221W determines congenital pain insensitivity with no overt cognitive disabilities, whereas V232fs and R121W also result in intellectual disability, thus showing similarities to HSAN IV, which is caused by mutations in TrkA, rather than to HSAN V. Comparing the cellular, biochemical and clinical findings of these mutations could help in better understanding not only the possible mechanisms underlying HSAN V, but also mechanisms of NGF signalling and roles. These mutations alter the balance between NGF and proNGF in favour of an accumulation of the latter, suggesting a possible role of proNGF as a molecule with an analgesic role. Furthermore, the neurotrophic and pronociceptive functions of NGF are split by the R221W mutation, making NGF variants based on this mutation interesting for designing therapeutic applications for many diseases. This review emphasizes the possibility of using the mutations involved in "painlessness" clinical disorders as an innovative approach to identify new proteins and pathways involved in pain transmission and perception. OUTSTANDING QUESTIONS: Why do homozygous HSAN V die postnatally? What is the cause of this early postnatal lethality? Is the development of a mouse or a human feeling less pain affecting higher cognitive and perceptual functions? What is the consequence of the HSAN V mutation on the development of joints and bones? Are the multiple fractures observed in HSAN V patients due exclusively to the carelessness consequent to not feeling pain, or also to an intrinsic frailty of their bones? Are heterodimers of NGF^WT and NGF^R221W in the heterozygote state formed? And if so, what are the properties of these heterodimeric proteins? How is the processing of proNGF^R221W to NGF^R221W affected by the mutation?

The role of the anterior pretectal nucleus in pain modulation: A comprehensive review

Descending pain modulation involves multiple encephalic sites and pathways that range from the cerebral cortex to the spinal cord. Behavioral studies conducted in the 1980s revealed that electrical stimulation of the pretectal area causes antinociception dissociation from aversive responses. Anatomical and physiological studies identified the anterior pretectal nucleus and its descending projections to several midbrain, pontine, and medullary structures. The anterior pretectal nucleus is morphologically divided into a dorsal part that contains a dense neuron population (pars compacta) and a ventral part that contains a dense fiber band network (pars reticulata). Connections of the two anterior pretectal nucleus parts are broad and include prominent projections to and from major encephalic systems associated with somatosensory processes. Since the first observation that acute or chronic noxious stimuli activate the anterior pretectal nucleus, it has been established that numerous mediators participate in this response through distinct pathways. Recent studies have confirmed that at least two pain inhibitory pathways are activated from the anterior pretectal nucleus. This review focuses on rodent anatomical, behavioral, molecular, and neurochemical data that have helped to identify mediators of the anterior pretectal nucleus and pathways related to its role in pain modulation.

Pain, Smell, and Taste in Adults: A Narrative Review of Multisensory Perception and Interaction

Every day our sensory systems perceive and integrate a variety of stimuli containing information vital for our survival. Pain acts as a protective warning system, eliciting a response to remove harmful stimuli; it may also be a symptom of an illness or present as a disease itself. There is a growing need for additional pain-relieving therapies involving the multisensory integration of smell and taste in pain modulation, an approach that may provide new strategies for the treatment and management of pain. While pain, smell, and taste share common features and are strongly linked to emotion and cognition, their interaction has been poorly explored. In this review, we provide an overview of the literature on pain modulation by olfactory and gustatory substances. It includes adult human studies investigating measures of pain threshold, tolerance, intensity, and/or unpleasantness. Due to the limited number of studies currently available, we have structured this review as a narrative in which we comment on experimentally induced and clinical pain separately on pain–smell and pain–taste interaction. Inconsistent study findings notwithstanding, pain, smell, and taste seem to interact at both the behavioral and the neural levels. Pain intensity and unpleasantness seem to be affected more by olfactory substances, whereas pain threshold and tolerance are influenced by gustatory substances. Few pilot studies to date have investigated these effects in clinical populations. While the current results are promising for the future, more evidence is needed to elucidate the link between the chemical senses and pain. Doing so has the potential to improve and develop novel options for pain treatment.

Multimodal spatio-temporal deep learning approach for neonatal postoperative pain assessment

The current practice for assessing neonatal postoperative pain relies on bedside caregivers. This practice is subjective, inconsistent, slow, and discontinuous. To develop a reliable medical interpretation, several automated approaches have been proposed to enhance the current practice. These approaches are unimodal and focus mainly on assessing neonatal procedural (acute) pain. As pain is a multimodal emotion that is often expressed through multiple modalities, the multimodal assessment of pain is necessary especially in case of postoperative (acute prolonged) pain. Additionally, spatio-temporal analysis is more stable over time and has been proven to be highly effective at minimizing misclassification errors. In this paper, we present a novel multimodal spatio-temporal approach that integrates visual and vocal signals and uses them for assessing neonatal postoperative pain. We conduct comprehensive experiments to investigate the effectiveness of the proposed approach. We compare the performance of the multimodal and unimodal postoperative pain assessment, and measure the impact of temporal information integration. The experimental results, on a real-world dataset, show that the proposed multimodal spatio-temporal approach achieves the highest AUC (0.87) and accuracy (79%), which are on average 6.67% and 6.33% higher than unimodal approaches. The results also show that the integration of temporal information markedly improves the performance as compared to the non-temporal approach as it captures changes in the pain dynamic. These results demonstrate that the proposed approach can be used as a viable alternative to manual assessment, which would tread a path toward fully automated pain monitoring in clinical settings, point-of-care testing, and homes.

The association of comfort and vision in soft toric contact lens wear

PURPOSE

This work set out to investigate if there was an association between subjective comfort and both subjective and measured vision during the use of contemporary daily disposable soft toric contact lenses.

METHODS

Thirty-eight habitual soft contact lens wearers wore each of three daily disposable toric lenses for one week in a prospective, crossover, randomised, single-masked study. The following clinical measures were recorded at dispensing and follow-up visits: biomicroscopy scores, lens fitting (including rotation and rotational stability), high and low contrast visual acuity, subjective vision quality and subjective ocular surface comfort. Subjective scores were collected using 0-10 numerical grading scales. Comfort scores were analysed using a linear regression model with age, sex, visit, phase of crossover ('phase'), lens type, lens rotation, lens rotational stability, visual acuity, cylinder power and subjective vision quality as factors of interest and then refined using backward stepwise regression.

RESULTS

Thirty six participants (31.1 ± 13.5 years) completed the study. Comfort scores were found to be associated with subjective vision quality (F = 127.0 ; p < 0.0001), phase (F = 7.2; p = 0.001) and lens type (F = 4.9; p = 0.009). Greater comfort scores were observed with greater subjective vision quality scores. Visual acuity was not statistically significant in the model.

CONCLUSION

This work suggests that symptoms of ocular discomfort may be more intense if there is also perceived visual compromise in daily disposable soft toric lenses. There was a stronger positive correlation between comfort and subjective vision quality compared with comfort and measured visual acuity.

Correlation Between Aspects of Perceived Patient Loneliness and Spinal Cord Stimulation Outcomes

OBJECTIVES

Loneliness as a whole has been characterized as a health-related risk factor and is associated with worse outcomes after cardiac procedures. Evidence suggests that chronic pain patients are particularly vulnerable to feeling lonely. We examined the relationship between different aspects of loneliness and one-year postoperative outcomes after spinal cord stimulation (SCS) for chronic pain.

MATERIALS AND METHODS

We contacted 69 patients with thoracic SCS who had participated in our prospective outcomes database with one-year follow-up to complete the validated, abbreviated UCLA Loneliness Scale (UCLA-3). We examined responses on question 9 of the Oswestry Disability Index (ODI), question 12 of the Beck Depression Inventory (BDI), and UCLA-3 due to their relevance to different aspects of loneliness. We conducted regression analyses to determine the relationship between aspects of loneliness and pain outcomes.

RESULTS

We identified that loss of interest in people, companionship, and feeling excluded were associated with pain outcomes. Loss of interest in people was associated with improvement in pain (NRS worst p = 0.021, r = 0.32, NRS least p = 0.004, r = 0.4; NRS right now p = 0.016, r = 0.33). Companionship and feeling excluded were also associated with pain. We examined the interface between depression and total loneliness and found that while both were related to each other, depression was not associated with pain outcomes.

CONCLUSIONS

This study demonstrates an association between loss of interest in people, companionship, and feeling excluded and worse postoperative pain outcomes after receiving SCS. It identifies aspects of loneliness as important factors to consider when predicting the outcomes of SCS therapy for chronic pain control.

Differential effects of visually induced analgesia and attention depending on the pain stimulation site

BACKGROUND

The term 'visually induced analgesia' describes a reduced pain perception induced by watching the painful body part as opposed to watching a neutral object. In chronic back pain patients, experimental pain, movement-induced pain and habitual pain can be reduced with visual feedback. Visual feedback can also enhance the effects of both massage treatment and manual therapy. The impact of somatosensory attentional processes remains unclear.

METHODS

In the current study, participants received painful electrical stimuli to their thumb and back while being presented with either a real-time video of their thumb or back (factor feedback). In addition, using an oddball paradigm, they had to count the number of deviant stimuli, applied to either their back or thumb (factor attention) and rate the pain intensity.

RESULTS

We found a significant main effect for attention with decreased pain ratings during attention. There was no main effect for visual feedback and no significant interaction between visual feedback and attention. Post-hoc tests revealed that the lowest pain intensity ratings were achieved during visual feedback of the back/ thumb and counting at the back/ thumb.

CONCLUSION

These data suggest that the modulation of perceived acute pain by visually induced analgesia may be influenced by a simultaneous somatosensory attention task.

SIGNIFICANCE

Somatosensory attention reduced experimental pain intensity in the thumb and back in the presence of both congruent and incongruent visual feedback. We found no significant visual feedback effect on the complex interplay between visual feedback and somatosensory attention.

Valuing life and evaluating suffering in infants with life-limiting illness

In this paper, we explore three separate questions that are relevant to assessing the prudential value of life in infants with severe life-limiting illness. First, what is the value or disvalue of a short life? Is it in the interests of a child to save her life if she will nevertheless die in infancy or very early childhood? Second, how does profound cognitive impairment affect the balance of positives and negatives in a child's future life? Third, if the life of a child with life-limiting illness is prolonged, how much suffering will she experience and can any of it be alleviated? Is there a risk that negative experiences for such a child (suffering) will remain despite the provision of palliative care? We argue that both the subjective and objective components of well-being for children could be greatly reduced if they are anticipated to have a short life that is affected by profound cognitive impairment. This does not mean that their overall well-being will be negative, but rather that there may be a higher risk of negative overall well-being if they are expected to experience pain, discomfort, or distress. Furthermore, we point to some of the practical limitations of therapies aimed at relieving suffering, such that there is a risk that suffering will go partially or completely unrelieved. Taken together, these considerations imply that some life-prolonging treatments are not in the best interests of infants with severe life-limiting illness.

Emerging Promise of Cannabinoids for the Management of Pain and Associated Neuropathological Alterations in Alzheimer's Disease

Alzheimer's disease (AD) is an irreversible chronic neurodegenerative disorder that occurs when neurons in the brain degenerate and die. Pain frequently arises in older patients with neurodegenerative diseases including AD. However, the presence of pain in older people is usually overlooked with cognitive dysfunctions. Most of the times dementia patients experience moderate to severe pain but the development of severe cognitive dysfunctions tremendously affects their capability to express the presence of pain. Currently, there are no effective treatments against AD that emphasize the necessity for increasing research to develop novel drugs for treating or preventing the disease process. Furthermore, the prospective therapeutic use of cannabinoids in AD has been studied for the past few years. In this regard, targeting the endocannabinoid system has considered as a probable therapeutic strategy to control several associated pathological pathways, such as mitochondrial dysfunction, excitotoxicity, oxidative stress, and neuroinflammation for the management of AD. In this review, we focus on recent studies about the role of cannabinoids for the treatment of pain and related neuropathological changes in AD.

Composite Score Is a Better Reflection of Patient Response to Chronic Pain Therapy Compared With Pain Intensity Alone

OBJECTIVE

The pain Numeric Rating Scale (NRS) score became standard when pain was introduced as the fifth vital sign in the 1990s. Although plagued with issues, it remains the basis for primary outcome measures in clinical trials for chronic pain therapies. Multidimensional composite scoring that considers all aspects of the chronic pain experience may provide a more meaningful response measure. Herein we propose a multidimensional responder index.

MATERIALS AND METHODS

Data were extracted from an ongoing prospective, multicenter study on DeRidder Burst spinal cord stimulation (B-SCS) for chronic back and/or leg pain (NCT03082261). The analysis cohort consisted of subjects who completed the NRS, Pain Catastrophizing Scale (PCS), EuroQol-5D (EQ-5D), and eight-item Patient-Reported Outcomes Measurement Information System Physical Function preoperatively and at 12 months after implant.

RESULTS

A principal component analysis showed that each of the four measures contributed equally to the variance in the data set, confirming that pain score should not be used alone. Subjects who failed to respond on NRS responded on both PCS and EQ-5D. Eighty-one percent of subjects responded on at least two measures. The responder algorithm yielded an 84% success rate at both 6- and 12-month time points.

CONCLUSIONS

Our study suggests that therapeutic response, similar to the chronic pain experience, is multidimensional. Careful consideration should be made to incorporate composite endpoints in future SCS clinical trials.

Pain after laparoscopic surgery: Focus on shoulder-tip pain after gynecological laparoscopic surgery

Laparoscopy, one of minimally invasive procedures, is a commonly used procedure in diagnosis and management of various kinds of clinical problems, including gynecologic organ-related diseases. Compared with conventional exploratory laparotomy, the benefits of laparoscopic surgery include reduction of surgical wound, decreasing in postoperative pain, shortening hospital stay, rapid recovery, and a better cosmetic result. However, there are still up to 80% of patients after laparoscopic surgery complaining of high levels of pain and needing pain relief. Postlaparoscopic pain can be separated into distinct causes, such as surgical trauma- or incision wound-associated inflammatory change, and pneumoperitoneum (carbon dioxide [CO2])-related morphological and biochemical changes of peritoneum and diaphragm. The latter is secondary to irritation, stretching, and foreign body stimulation, leading to phrenic neuropraxia and subsequent shoulder-tip pain (STP). STP is the most typical unpleasant experience of patients after laparoscopic surgery. There are at least 11 strategies available to attempt to decrease postlaparoscopic STP, including (1) the use of an alternative insufflating gas in place of CO2, (2) the use of low-pressure pneumoperitoneum in place of standard-pressure pneumoperitoneum, (3) the use of warmed or warmed and humidified CO2, (4) gasless laparoscopy, (5) subdiaphragmatic intraperitoneal anesthesia, (6) local intraperitoneal anesthesia, (7) actively expelling out of gas, (8) intraperitoneal drainage, (9) fluid instillation, (10) pulmonary recruitment maneuvers, and (11) others and combination. The present article is limited in discussing postlaparoscopic STP. We extensively review published articles to provide a better strategy to reduce postlaparoscopic STP.

Perception of phasic pain is modulated by smell and taste

BACKGROUND

Pain perception is a multimodal experience composed of sensory, emotional and cognitive dimensions. Accumulating evidence suggests that the chemical senses can influence pain perception, but their relation with phasic pain is still unknown. The aim of this study was to investigate the influence of smell and taste having different valence on phasic pain.

METHODS

Twenty-eight healthy volunteers received sweet, bitter and neutral odours or gustatory substances while receiving painful stimuli consisting of electrical shocks. Tactile threshold, pain threshold and pain tolerance were collected using the psychophysical method of limits at baseline and in association with smell and taste. Perception of pain intensity and unpleasantness was measured with a numerical rating scale.

RESULTS

Sweet smell induced lower ratings of pain intensity than bitter smell when stimuli were delivered at pain threshold. Sweet smell also induced lower ratings of pain unpleasantness than neutral smell when stimuli were delivered at pain tolerance. Sweet taste induced lower ratings of pain unpleasantness than bitter taste when stimuli were delivered at pain threshold. Conversely, pain threshold and pain tolerance per se were not affected by smell and taste.

CONCLUSIONS

These findings highlight an effect of sweet substances in reducing the subjective perception of pain intensity and unpleasantness associated to phasic pain.

SIGNIFICANCE

By demonstrating the link between smell, taste and phasic pain this study may have a translational impact in clinical conditions characterized by so-called shock-like pain, such as neuropathic pain.