Slowing in Peak-Alpha Frequency Recorded After Experimentally-Induced Muscle Pain is not Significantly Different Between High and Low Pain-Sensitive Subjects

Peak alpha frequency (PAF) reduces during cutaneous pain, but no studies have investigated PAF during movement-related muscle pain. Whether high-pain sensitive (HPS) individuals exhibit a more pronounced PAF response to pain than low-pain sensitive (LPS) individuals is unclear. As a pain model, twenty-four participants received nerve growth factor injections into a wrist extensor muscle at Day 0, Day 2, and Day 4. At Day 4, a subgroup of twelve participants also undertook eccentric wrist exercise to induce additional pain. Pain numerical rating scale (NRS) scores and electroencephalography were recorded at Day 0 (before injection), Day 4, and Day 6 for 3 minutes (eyes closed) with wrist at rest (Resting-state) and extension (Contraction-state). The average pain NRS scores in contraction-state across Days were used to divide participants into HPS (NRS-scores≥2) and LPS groups. PAF was calculated by frequency decomposition of electroencephalographic recordings. Compared with Day 0, contraction NRS-scores only increased in HPS-group at Day 4 and Day 6 (P < .001). PAF in Contraction-state decreased in both groups at Day 6 compared with Day 0 (P = .011). Across days, HPS-group showed faster PAF than LPS-group during Resting-state and Contraction-state (P < .04). Average pain NRS-scores across days during Contraction-states correlated with PAF at Day 0 (P = .012). Pain NRS-scores were associated with PAF during Contraction-state at Day 4 and Day 6 (P < .05).PerspectivePAF was slowed during long-lasting movement-related pain in both groups, suggesting a widespread change in cortical excitability independent of the pain sensitivity. Moreover, HPS individuals showed faster PAF than LPS individuals during muscle pain, which may reflect a different cognitive, emotional, or attentional response to muscle pain among individuals.     

A psychophysical evaluation of the relationship between trait anxiety, pain perception, and induced state anxiety.

The present study examined the interactive effects of state and trait anxiety on pain threshold and subjective pain intensity. State anxiety was manipulated in 15 low trait anxious (LTA) individuals and 17 high trait anxious (HTA) individuals, who rated their anxiety level and subjective pain intensity in response to noxious electrical experimental pain stimuli. A difference in pain threshold between HTA and LTA participants was not found; however, higher state anxiety led to an increase in reported pain intensity for all participants. Furthermore, HTA individuals reported significantly higher levels of anxiety and pain intensity than LTA individuals across all pain and anxiety conditions. There was no interaction between state and trait anxiety on pain perception and anxiety ratings. These findings show an additive rather than synergistic effect between state-trait anxiety and subjective pain intensity. PERSPECTIVE: Use of anxiety-reducing techniques for individuals experiencing pain might reduce the perceived severity/intensity of pain. Furthermore, individuals with higher trait anxiety (a greater disposition to experience anxiety) might benefit from these techniques because higher trait anxious individuals tend to exacerbate perceived pain stimulations more than lower trait anxious individuals.     

Assessment of chronic pain. I. Aspects of the reliability and validity of the visual analogue scale

The visual analogue scale (VAS) is a simple and frequently used method for the assessment of variations in intensity of pain. In clinical practice the percentage of pain relief, assessed by VAS, is often considered as a measure of the efficacy of treatment. However, as illustrated in the present study, the validity of VAS estimates performed by patients with chronic pain may be unsatisfactory. Two types of VAS, an absolute and a comparative scale, were compared with respect to factors influencing the reliability and validity of pain estimates. As shown in this study the absolute type of VAS seems to be less sensitive to bias than the comparative one and is therefore preferable for general clinical use. Moreover, the patients appear to differ considerably in their ability to use the VAS reliably. When assessing efficacy of treatment attention should therefore be paid to several complementary indices of pain relief as well as to the individual's tendency to bias his estimates.     

Race and histories of mood disorders modulate experimental pain tolerance in women.

Thirty-two African American and 23 non-Hispanic white women were compared for experimental pain threshold and tolerance to thermal, ischemic, and cold pressor pain. Approximately half of each group had prior mood disorders (17 African Americans, 13 non-Hispanic whites), though all were free of current mood disturbance. Women with prior mood disorders were less sensitive to ischemic pain than women with no prior mood disorders (P < .05), whereas African Americans were more sensitive to ischemic pain than non-Hispanic whites, though only at pain tolerance (P < .001). For cold pressor pain, the effects of race were only seen in women with prior mood disorders, since African Americans with prior mood disorders were more sensitive than non-Hispanic whites with prior mood disorders (P < .05). These results indicate that experimental pain sensitivity in women is influenced by both race and histories of mood disorders. PERSPECTIVE: We examined the association of race and histories of mood disorders with experimental pain sensitivity in an exclusively female sample. Our findings for racial differences in pain sensitivity may have implications for greater clinical pain in African American women. Persistent disturbance in pain modulatory mechanisms in women with a history of mood disorders may also have implications for the development of subsequent mood disturbances.     

Age-related changes in nociception and effect of morphine in the Lou rat.

Little is known about how the ageing process affects pain sensitivity and a relevant animal model is therefore required. The effect of age on pain reactivity in animals has been investigated by several experimenters but the results are conflicting. Four groups of male and female Lou/C/Jall rats (4-29 months old) were used for our study. Four pain tests based on evaluation of reflex or more integrated behaviours after a thermal (tail immersion test) or mechanical (paw pressure test and von Frey test) stimulation were used. With mechanical stimulus, a significant decrease in the pain threshold across age was observed, females were more sensitive than males. This increase in nociceptive sensitivity to mechanical stimulation was more pronounced on integrated behaviours (struggle reaction) than on withdrawal reflex. An age-related increase in sensitivity was found on von Frey test. No effect on the latency of reflex induced by thermal stimulation was observed. In addition, a decrease in the spontaneous motor activity during exploration was observed across ageing; this effect was more marked for the females. The effect of morphine at doses of 1, 3 and 9 mg/kg (s.c.) decreased in intensity across ageing. These data demonstrate the need to use (1) various noxious stimuli because differences were observed in the modification of pain reactivity according to the nature of the stimulus; (2) various pain parameters and particularly integrated behaviours; (3) several age groups. In addition, Lou/C/Jall rat could be a useful model for studying of effect of age on pain.     

The prevalence of pain complaints in a general population

The authors argue that the study of the complaint of pain falls within the purview of epidemiological study. An analytic survey of 500 randomly selected households on the roster of a group family practice clinic was undertaken. The purpose was to determine the self-reported prevalence rates of any pain complaint and to determine the distribution of pain rates according to selected demographic and socioeconomic variables. Sixteen percent of the individuals sampled from a family practice (H.S.O.) had experienced pain within the 2 weeks preceding the survey. The prevalence rate of those with persistent pain was approximately twice that of those with temporary pain. More women than men reported temporary and persistent pain. The age specific morbidity rate for persistent pain increased with age. The back, lower extremities, and head and face were the most frequently identified sites of pain in both subgroups. Persons with persistent pain used health services, both community physicians and hospital care, more frequently than did those with temporary pain. No significant differences between the two groups were reported for physical, social or emotional function although the persistent pain group characterized their general health status more poorly.     

Age, pain, and coping with rheumatoid arthritis.

The purpose of this study was to examine the relationship of age and pain severity (i.e. mild versus severe pain) in predicting coping strategies of individuals with rheumatoid arthritis (RA). An age-stratified sample (N = 121) of individuals diagnosed with rheumatoid arthritis completed a modified version of the Coping Strategies Questionnaire (CSQ). Individuals were asked to report the coping strategies used for mild versus severe pain. Findings included: (1) older adults were more likely than younger adults to report use of maladaptive coping strategies in the context of mild, but not severe, RA pain, (2) older adults' reported patterns of coping reflected less-than-anticipated expertise in dealing with RA pain, and (3) individuals, regardless of age, reported use of more active coping strategies in the context of mild pain and use of more maladaptive coping strategies in the context of severe pain. The present study suggests that research regarding illness and coping is most informative when it captures the individual-situational interaction of dealing with stressors such as chronic pain.     

Investigating the effects of anxiety sensitivity and coping on the perception of cold pressor pain in healthy women.

Research indicates that anxiety sensitivity may be related to the negative experience of pain, especially amongst women. Further evidence with chronic pain patients indicates that anxiety sensitivity may result in avoidance pain-coping strategies. However, this effect has not yet been experimentally investigated in healthy groups. Therefore, the current study sought to investigate the effect of anxiety sensitivity and coping on women's responses to pain. Thirty women who were classified as high in anxiety sensitivity and 30 women classified as low in anxiety sensitivity participated. Within each anxiety sensitivity group, half the participants (n = 15) were randomly instructed to either focus on or avoid cold pressor pain sensations. As expected, women high in anxiety sensitivity were found to report higher levels of sensory and affective pain. Also, and consistent with previous research into anxiety sensitivity, no differences were found between anxiety sensitivity groups for measures of pain threshold or pain tolerance. The pain coping instruction manipulation was found to moderate pain experience, in that the avoidance strategy resulted in higher pain ratings compared to when instructed to focus. Finally, high anxiety sensitive women reported greater pain when instructed to avoid rather than focus on cold pressor pain. These results are discussed in light of previous research and future directions for pain management.     

Cryohypophysectomy for bone pain of metastatic breast cancer.

In a series of 22 patients, cryohypophysectomy gave relief of bone pain from metastatic breast cancer for 3 months in 55% of patients and for 6 months in 32% of patients. On average they were pain free for 55% of their remaining life. Advantages of this technique are the avoidance of a major operation, the mild disturbance to the patient, a short hospital stay and the paucity of significant complications apart from a need for hormone replacement.     

Individual Variation in Pain Sensitivity and Conditioned Pain Modulation in Acute Low Back Pain: Effect of Stimulus Type,Sleep, and Psychological and Lifestyle Factors

Generalized hyperalgesia and impaired pain modulation are reported in chronic low back pain (LBP). Few studies have tested whether these features are present in the acute phase. This study aimed to test for differences in pain presentation in early-acute LBP and evaluate the potential contribution of other factors to variation in sensitivity. Individuals within 2 weeks of onset of acute LBP (n?=?126) and pain-free controls (n?=?74) completed questionnaires related to their pain, disability, behavior, and psychological status before undergoing conditioned pain modulation (CPM) and pain threshold (heat, cold, and pressure) testing at the back and forearm/thumb. LBP participants were more sensitive to heat and cold at both sites and pressure at the back than controls, without differences in CPM. Only those with high-pain (numeric rating scale ≥4) were more sensitive to heat at the forearm and pressure at the back. Four subgroups with distinct features were identified: “high sensitivity,” “low CPM efficacy,” “high sensitivity/low CPM efficacy,” and “low sensitivity/high CPM efficacy.” Various factors such as sleep and alcohol were associated with each pain measure. Results provide evidence for generalized hyperalgesia in many, but not all, individuals during acute LBP, with variation accounted for by several factors. Specific pain phenotypes provide candidate features to test in longitudinal studies of LBP outcome.

Acute versus chronic pain treatment in Alzheimer's disease.

Several studies have suggested a lower consumption of analgesics in patients with Alzheimer's disease (AD) than in cognitively intact individuals (ND), but little attention has been paid to a distinction in analgesic consumption between acute and chronic pain treatment. The aim of this prospective and longitudinal study is a comparison in AD and ND residents at selection, and one year later, of analgesic consumption for acute and chronic pain, with an assessment of cognitive status (with the Mini Mental State Examination (MMSE)). Three hundred institution residents (150 AD and 150 ND), 20% male and 80% female (84.4 +/- 8.3 years old), were included in this study. Analgesic consumption and MMSE were reassessed at one year's distance (period 1 P1 and 2 (P2)). Analgesic consumption for acute pain was not significantly different for AD and ND at selection time or one year later, while MMSE declined significantly for AD (6 +/- 7 (P1) versus 4 +/- 6 (P2) p < 0.01, and ND individuals 23 +/- 5 (P1) versus 20 +/- 6 (P2), p < 0.01, respectively). Chronic pain analgesic consumption however was significantly lower in AD than in ND (p < 0.01). These findings may suggest a dissociation between sensory-discriminative (lateral pain system) and motivational-affective (medial pain system) aspects of pain in individuals with AD. This dissociation must be further investigated as it may have important consequences for pain evaluation and pain treatment in this vulnerable population.     

Coping strategies and life satisfaction in subgrouped fibromyalgia patients

The present study describes pain- and stress-coping strategies and life satisfaction in subgroups of fibromyalgia patients. Thirty-two females with fibromyalgia syndrome (FMS) and 21 healthy pain-free women were studied. Those with FMS were classified as thermal (both heat and cold) pain sensitive or slightly cold pain sensitive based on pain thresholds determined using a Thermotest device. Global stress-coping styles, life satisfaction, and specific pain-coping strategies were measured. Patients classified as thermal pain sensitive were affected by physical symptoms to a greater extent than were those classified as slightly cold pain sensitive. The thermal pain sensitive group used more diverting attention coping strategies than the slightly cold pain sensitive group did. Separating fibromyalgia patients into subgroups might increase the potential for improving nursing care of these patients. Through the use of effective coping strategies in dealing with stress and pain, life satisfaction may also be enhanced.     

Flow cytometric analysis of reticulocytes using an RNA-binding fluorochrome.

The reticulocyte count is an important parameter in the diagnosis of anaemia. The commonly used microscopic counting technique is, however, laborious and hampered by poor precision and low sensitivity. An alternative method has recently been developed, which is based on flow cytometric identification and quantification of reticulocytes after staining with an RNA-binding fluorochrome, thiazol orange. The two methods were compared both in a sample of healthy individuals and in patient specimens. The correlation between the methods was good, but the flow cytometric analysis consistently gave values approximately 1.5 times higher (reticulocytes in per cent of erythrocytes) than the microscopic technique. The coefficient of variation was significantly lower for the flow cytometric technique. Reference values for the reticulocyte count were determined and the effects of storage of specimens were evaluated. It is concluded that flow cytometric analysis of reticulocytes is more sensitive and has a better precision that the standard microscopic procedure.     

Shared Sensitivity to Physical Pain and Social Evaluation

Many studies have demonstrated a link between experiences of physical pain and those of social rejection, both of which can trigger cognitive processes involved in detecting, orienting toward, or reacting to potentially threatening events. This study tested the hypothesis that healthy individuals who are more sensitive to physical pain are also more sensitive to social rejection. We recruited participants with high or low pain-sensitivity (HPS and LPS), as assessed by scores on a pain-sensitivity questionnaire and confirmed by experimental pain-sensitivity assessment. A modified social-judgment task was adopted in which participants first provided expectations about being liked/disliked by “peers”, and then received “peers” feedback indicating acceptance or rejection. While both groups rated rejection as more unpleasant than acceptance, this difference was greater in the HPS group. Electroencephalographic results showed that only participants in the HPS group exhibited greater early delta/theta-oscillations (δ/θ-oscillations) in response to rejection than to acceptance, regardless of whether the feedback was expected or unexpected. However, both groups consistently exhibited greater late δ/θ-oscillations in response to rejection when the feedback was unexpected. These results suggest that participants in the HPS group were more sensitive to social cues signaling acceptance or rejection at early stages of information processing. Furthermore, neither early nor late δ/θ-oscillations following nonsocial feedback (correct or incorrect time-estimation) differed between groups. Altogether, these results supported the idea of shared sensitivity in detecting potentially physical and social threats in the environment.PerspectivesThis study showed the greater emotional reactions and early-latency δ/θ-oscillations in response to social evaluation among healthy individuals with high pain sensitivity. It supports the idea of shared sensitivity to physical pain and social evaluation, which could be governed by a common system for detecting and monitoring potentially environmental threats.     

Individuals With Chronic Neck Pain Have Lower Neck Strength Than Healthy Controls: A Systematic Review With Meta-Analysis

ObjectiveThe aim is to verify whether there is difference in neck strength between healthy individuals and individuals with chronic neck pain.MethodsThe PubMed, Embase, and Scopus databases were searched. Two independent reviewers selected relevant full articles comparing neck strength between healthy individuals and individuals with chronic neck pain. Two independent reviewers extracted the data from the full articles selected. A meta-analysis was used to assess standardized mean differences in neck strength based on a random-effects model (Prospero number CRD42017081502).ResultsThe search returned 3554 results; 15 articles were included. The chronic neck pain group showed lower neck strength compared with healthy individuals. The standardized mean difference was -0.90 (95% confidence interval [CI] = -1.13 to -0.67) for flexion, -0.79 (95% CI = -0.99 to -0.60) for extension, -0.74 (95% CI = -1.03 to -0.45) for right lateral flexion, and -0.75 (95% CI = -1.04 to -0.46) for left lateral flexion.ConclusionBased on this meta-analysis with a 3a level of evidence, individuals with chronic neck pain have lower neck strength for flexion, extension, and the lateral flexion of the neck than healthy controls.     

Effects of a brief and economical intervention in preparing patients for surgery: does coping style matter?

The objective of this study was to examine the effects of a brief and economical procedure in the preparation of surgical patients. More specifically, the study was intended to test whether patient's monitoring style (high vs. low) makes any difference to the benefits of a relaxation technique. Ninety-two patients scheduled for hysterectomy with double oophorectomy were assessed for preferred coping style and randomly assigned to one of two conditions: (a) relaxation training and (b) attention control. It was hypothesized that low monitors would report less pain, less analgesic use and a higher activity level when trained in relaxation than low monitor controls or than high monitors trained in relaxation. Results showed no differences between individuals with different coping styles. On the other hand, however, statistically significant differences were observed between trained patients and controls. Namely, individuals trained in relaxation experienced less pain along the surgical process, pain interfered less with their daily activities, and performed a higher activity level three weeks after surgery, compared to non trained patients.     

Sensitivity of pain rating scales in an endoscopy trial

OBJECTIVE: The purpose of this study was to compare the sensitivity of two commonly used pain-rating scales, the Visual Analog Scale and the 4-point verbal rating scale. Both are considered reliable and valid, but previous studies regarding sensitivity of rating scales have lead to different conclusions, and there is no firm agreement as to the best scale to choose. METHODS: The sensitivity of the Visual Analog Scale and the 4-point verbal rating scale was compared by stochastic simulation. In the simulation model, we used 168 pairs of pain ratings on the Visual Analog Scale and the 4-point verbal rating scale from individuals undergoing a lower gastrointestinal endoscopy, maintaining the true relation between ratings from the same individual. We created empirical distributions mimicking 2 independent groups of pain ratings. Random samples from the 2 groups were compared by the Wilcoxon-Mann-Whitney U test in 10,000 repetitions of a computer algorithm. By increasing the proportion of individuals with a high level of pain in one group, we increased the true difference between pain ratings and estimated a statistical power function. RESULTS: In the present pain model with pain ratings from healthy individuals undergoing endoscopy, the Visual Analog Scale is consistently more sensitive than the four-point verbal rating scale. DISCUSSION: Because each individual provided one Visual Analog Scale and one 4-point verbal rating scale rating for the same pain experience, the ability of the two scales to detect differences between groups of pain ratings could be compared. The use of a simulation model enabled estimation of a power function and reduced the probability of basing the conclusion on a chance finding.     

Possible involvement of opioid peptides of caudate nucleus in acupuncture analgesia

Rabbits chronically implanted with permanent cannulae were used in brain perfusion and microinjection experiments. Potassium iontophoresis applied to the rabbits' ear skin served as a noxious stimulus and the electric current used to elicit the defense response was taken as the pain threshold. The brain perfusate was analysed by radioreceptor assay and the level of endogenous opioid peptides (EOP) was expressed as competition rate. Electroacupuncture (EA) elicited an increase in pain threshold and a rise in EOP level in the perfusate from the anterior part of the head of the caudate nucleus (n = 10, P less than 0.002) but not from the posterior part. The pain threshold raising effect of EA could readily be reversed by microinjection of naloxone into the anterodorsal part of the head of the caudate (n = 12, P less than 0.01). With the techniques of multimicropipettes and microiontophoresis, caudate neuronal activity was recorded and examined in acute animals anesthetized with chloralose and urethane. It was found that microiontophoresed etorphine produced a strong, naloxone reversible inhibition of the spontaneous activity of the caudate neurons (61/162). Most etorphine sensitive neurons were identified in the dorsal part of the head of the caudate (P less than 0.01). EA produced inhibition of some etorphine sensitive neurons (16/35) and the inhibition could also be reversed by microiontophoresis of naloxone (4/8). The results indicate the participation of intracaudate opioid peptides in acupuncture analgesia.     

Discomfort and pain from loaded passive joint structures

Sensations of strain and pain from healthy elbow and knee joints kept in an extreme position were reported on Borg's category-ratio scale (4) by 12 male volunteers in an experimental situation. The purpose of the study was to find out whether passive joint structures give sensations of discomfort and pain when moderately loaded for a certain time in an extreme position. Sensations of discomfort and pain were reported every 15th second. The mean values of ratings followed a straight line of increasing values during the first four minutes. Great variations were found between individuals. The elbow joint was six times more sensitive to the loading dose expressed as the product of the moment of force and time than was the knee joint. After the load was removed the provoked sensation slowly decreased. Sometimes the initial after-load rating was higher than the last rating with the load. The results imply that static work postures should also be analyzed with respect to joint position.     

Cancer pain intensity measurement: concurrent validity of three tools--finger dynamometer, pain intensity number scale, visual analogue scale

Although the visual analogue scale (VAS) and number scales are known to be valid and sensitive measures of pain intensity, some older individuals are unable to use them. For individuals who lack the ability to use these scales, valid alternative measures of pain intensity would be useful for research and clinical practice. The purpose of this study was to examine the concurrent validity of a new measure of pain intensity, the Finger Dynamometer (FD), in a sample of 15 adults with advanced stage cancer pain. In a repeated measures correlational design each patient rated present pain intensity using the FD, a Pain Intensity Number Scale (PINS), and a VAS at four separate times. Data analyses using Kendall Correlational Coefficients indicated weak to moderate correlation between the FD and PINS (gamma = .47 to .68; p less than .01) and between the FD and VAS (gamma = .38 to .46; p less than .05) at each measurement time. Strong correlation was found between the VAS and the PINS (gamma = .77 to .89; p less than .001). Findings support the concurrent validity of the VAS and the PINS but indicate that further research is necessary to establish the psychometric properties of the FD as a measure of pain intensity in chronic pain models, such as cancer pain. Recommendations are made regarding important variables to be considered in further research with the FD.