Pain-free Control Subjects Research Articles

Catastrophizing and Pain-Coping in Young Adults: Associations With Depressive Symptoms and Headache Pain

Cognitive and behavioral pain-coping strategies, particularly catastrophizing, are important determinants of the pain experience. Most studies of pain-coping are performed in samples of treatment-seeking patients with longstanding pain complaints. Individual differences in pain-coping styles may also significantly affect day-to-day pain and quality of life in nonclinical samples, though this has rarely been investigated. In particular, headache pain is common in the general population, and little is known about how pain-related coping affects pain and quality of life among headache sufferers from a nonclinical setting. In this study, 202 generally healthy subjects were divided into 2 groups, those who reported problem headaches and pain-free control subjects. Reports of pain-related catastrophizing and the use of active pain-coping strategies did not differ between the groups, but differential associations between pain-coping strategies and emotional functioning were observed. Specifically, within the headache group only, those reporting higher levels of pain catastrophizing and lower levels of active pain-coping showed the highest level of depressive symptoms. Further, higher catastrophizing was associated with greater headache pain and pain-related interference. These findings suggest that catastrophizing has little influence on emotional functioning in those without ongoing pain complaints and highlight the importance of coping in modulating the consequences of pain on day-to-day functioning, even in samples from nonclinical settings. Moreover, these findings indirectly suggest that interventions that increase adaptive coping and decrease catastrophizing may help to buffer some of the deleterious functional consequences of headache pain. This study adds to a growing literature that conceptualizes catastrophizing as a diathesis, or risk factor, for deleterious pain-related consequences. These data suggest that catastrophizing may require the presence of a pain condition before its detrimental effects are exerted.

Temperament and character personality profiles and personality disorders in chronic pain patients

In his psychobiological model of personality, Cloninger developed a novel approach concerning the relationships between psychopathological syndromes and personality. We investigated 207 chronic pain patients (CPPs) and compared them to 105 pain-free control subjects. Participants were assessed using the Temperament and Character Inventory (TCI), the Structured-Clinical-Interview-II, the Beck Depression Inventory and the Spielberger Anxiety Inventory. The CPPs scored higher on the depression and state anxiety scales and 41% fulfilled the criteria of having at least one personality disorder (PD). We used a covariance analysis to control for depression and state anxiety and found that the CPPs scored higher on the Harm Avoidance Temperament Dimension and lower on the Self-Directedness and Cooperativeness Character Dimensions. In CPPs, the symptom counts of all PD subtypes were significantly related to low Self-Directedness and, to a lesser degree, low Cooperativeness. The PD symptoms in Cluster A were related to low Reward Dependence, those in Cluster B were related to high Novelty Seeking and the PD symptoms in Cluster C were related to high Harm Avoidance. In multiple hierarchical regression analyses, controlling for age, gender, depression and state anxiety, TCI scales predicted on average 23% in PD symptom counts. The Self-Directedness and Cooperativeness personality traits appeared to be significant predictors in determining the presence or absence of a PD by correctly classifying 75.8% of CPPs. The TCI provides further insight into the mechanisms underlying the development of chronic pain. This useful diagnostic instrument helps to economically and validly facilitate the identification of core PD features.

Is cartilage thickness different in young subjects with and without patellofemoral pain?

To determine the differences in load-bearing patellofemoral joint cartilage thickness between genders. To determine the differences in load-bearing cartilage thickness between pain-free controls and individuals with patellofemoral pain. The articular cartilage thickness of the patella and anterior femur was estimated from magnetic resonance images in 16 young, pain-free control subjects (eight males, eight females) and 34 young individuals with patellofemoral pain (12 males, 22 females). The average age of all subjects was 28+/-4 years. The cartilage surfaces were divided into regions approximating the location of patellofemoral joint contact during knee flexion. The mean and peak cartilage thicknesses of each region were computed and compared using a repeated-measures Analysis of Variance. On average, males had 22% and 23% thicker cartilage than females in the patella (P < 0.01) and femur (P < 0.05), respectively. Male control subjects had 18% greater peak patellar cartilage thickness than males with patellofemoral pain (P < 0.05); however, we did not detect differences in patellar cartilage thickness between female control subjects and females with patellofemoral pain (P = 0.45). We detected no significant differences in femoral cartilage thickness between the control and pain groups. Thin cartilage at the patella may be one mechanism of patellofemoral pain in male subjects, but is unlikely to be a dominant factor in the development of pain in the female population.

Using myoelectric signal parameters to distinguish between computer workers with and without trapezius myalgia

Complaints of chronic trapezius muscle pain among computer workers have increased in prevalence during the last decade. Currently there is no clear understanding of the pathophysiological mechanisms involved in affected muscles. The major objective of this work was to determine if measurable electrophysiological differences exist between the trapezius muscles in individuals suffering from trapezius myalgia (TM) and occupation-matched pain-free control subjects. Myoelectric signal (MES) data were recorded from the upper trapezius muscle while subjects with and without myalgia performed a standardized series of postural and arm-holding tasks. MES variables reflecting muscle fatigue, muscle tension and motor control strategies were analyzed to determine their potential ability to distinguish between the two groups. One variable, RestTime, was found to be significantly different between the groups but it was not specific enough to predict group association. A multivariate logistic regression analysis yielded a model that separated the two groups with better than 70% sensitivity and 70% specificity. The variables included in the model reflect differences in trapezius muscle activity between the groups, particularly related to motor control and/or active muscle tension, but not fatigue. The model was tested using a small sample of new data, which again produced a good sensitivity (85.7%) but not specificity (42.9%). To the authors' knowledge, this is the first objective MES-based model that has successfully classified subjects with or without TM based on a simple clinical test. Further work with this model might result in understanding the pathophysiology of TM, assisting with clinical diagnosis, and testing the effect of various treatment interventions.

Sex differences in response to treatment and emerging therapies in the treatment of lung cancer

Macrophage migration inhibitory factor (MIF) is a cytokine produced by neuroendocrine and immune tissues that possesses several characteristics of a neuroendocrine mediator. Chronic pain is known to affect and to be affected by neuroendocrine and immune mechanisms. In the present study, the plasma levels of MIF and several hormones (cortisol, estradiol, testosterone) were determined to evaluate their mutual behaviour in controls and in chronic pain patients. Blood samples were collected from males and females divided into groups depending on their age (younger or older than 55) and health condition: (1) pain-free control subjects; (2) chronic non-malignant pain subjects. Moreover, two additional groups were added to evaluate the effects of short- and long-term opioid administration: (3) short-term opioid-treated chronic pain patients and (4) long-term opioid-treated chronic pain patients (longer than 6 months). MIF in control/younger men was higher than in all the other control and chronic pain groups. MIF was lower in pain patients than in controls of both sexes. MIF was not changed by morphine administration; its levels remained lower in opioid-treated subjects than in controls after both short- and long-lasting administration. Chronic pain changed hormone plasma levels differently in male and female patients. MIF was positively correlated with testosterone and negatively with estradiol. These results demonstrate sex differences in the younger men and women and a strong pain-induced decrease of MIF availability. These findings suggest the involvement of this cytokine in the sex differences observed in chronic pain conditions.

The Role of Fear of Movement and Injury in Selective Attentional Processing in Patients with Chronic Low Back Pain: A Dot-Probe Evaluation

The present study sought to investigate to what extent patients with chronic low back pain and pain-free control subjects selectively attend to pain-related stimuli as measured with 2 dot-probe tasks with word stimuli and pictorial stimuli. Selective attentional processing was measured by means of 3 indices: the bias index, a congruency effect, and an incongruency effect. Pain-related fear as a trait measure (Tampa Scale for Kinesiophobia [TSK]) was expected to be positively associated with all indices of selective attentional processing of pain stimuli. Results were analyzed with repeated-measures analysis of variance. An incongruency effect was found for patients and to a significantly less degree for pain-free control subjects on the dot-probe task with pictorial stimuli, indicating that pain patients have difficulty disengaging from threat pictures. Pain-related fear as a trait measure (TSK) was not associated with selective attentional processing of word and pictorial stimuli in either pain patients or control subjects. Results from the present study are discussed, and directions for future research are provided. Perspective Demonstrating difficulty to disengage from threat might be clinically relevant because patients might pay less attention to fear-disconfirming information and remain engaged in avoidance, which might eventually lead to prolonged anxiety states.

Gender-related effects of chronic non-malignant pain and opioid therapy on plasma levels of macrophage migration inhibitory factor (MIF)

Macrophage migration inhibitory factor (MIF) is a cytokine produced by neuroendocrine and immune tissues that possesses several characteristics of a neuroendocrine mediator. Chronic pain is known to affect and to be affected by neuroendocrine and immune mechanisms. In the present study, the plasma levels of MIF and several hormones (cortisol, estradiol, testosterone) were determined to evaluate their mutual behaviour in controls and in chronic pain patients. Blood samples were collected from males and females divided into groups depending on their age (younger or older than 55) and health condition: (1) pain-free control subjects; (2) chronic non-malignant pain subjects. Moreover, two additional groups were added to evaluate the effects of short- and long-term opioid administration: (3) short-term opioid-treated chronic pain patients and (4) long-term opioid-treated chronic pain patients (longer than 6 months). MIF in control/younger men was higher than in all the other control and chronic pain groups. MIF was lower in pain patients than in controls of both sexes. MIF was not changed by morphine administration; its levels remained lower in opioid-treated subjects than in controls after both short- and long-lasting administration. Chronic pain changed hormone plasma levels differently in male and female patients. MIF was positively correlated with testosterone and negatively with estradiol. These results demonstrate sex differences in the younger men and women and a strong pain-induced decrease of MIF availability. These findings suggest the involvement of this cytokine in the sex differences observed in chronic pain conditions.

Assessment of disability: Impact of chronic low back pain on dynamic lifting performance: A comparative study of older adults

An estimated 17 million older adults have experienced at least one episode of low back pain during the past year, and 6 million of these individuals suffer from chronic low back pain (CLBP). The consequences of CLBP are wide ranging, including impaired physical function, depression and anxiety, and increased use of health care resources. Measurement of physical function is critical in the comprehensive assessment of older adults with CLBP. Historically, studies of CLBP in older adults have used a narrow measure of physical function, such as spinal range of motion, isokinetic strength, and postural control. The performance of a functional task, however, requires physical capacity or a combination of these and other physical components to generate whole body movements for a sustained period. Performance differences between older adults with CLBP and a control group were evaluated during a repetitive isodynamic lifting task. Participants ranged in age from 65-84 and were 49 CLBP patients and 49 pain-free control subjects. Performance outcomes included weight lifted and number of lifts completed, and performance style measures described basic dynamic body biomechanics used during each lift. Controls completed significantly more lifts (p < 0.05) and lifted more weight than CLBP subjects (p < 0.01). Controls also lifted faster (p < 0.05), demonstrated less synchrony between hip and knee movements (p < 0.05), and displayed greater anterior-posterior sway (p < 0.05). The static and dynamic motion differences found between CLBP subjects and controls as they performed repetitive lifting under a constant load indicate that body motion parameters, in addition to more common strength and endurance measures, are necessary to describe the impact of CLBP on older adults' lifting abilities. These findings also suggest that CLBP may accelerate the functional decline associated with aging, which can ultimately lead to disability.

Body motion during repetitive isodynamic lifting: a comparative study of normal subjects and low-back pain patients

To quantify performance differences between patients with low-back pain (LBP) and a control group during their performance of a repetitive isodynamic lifting task. Case–control study was done. LBP patients were recruited and tested at an outpatient ambulatory chronic pain rehabilitation program before treatment was begun. Fifty-three LBP patients who had prolonged back pain and 53 age and gender matched pain-free control subjects. Overall lifting performance measures included weight lifting and number of lifts completed; kinematic measures of hip and knee movements during lifting were described by hyperbolic tangent models, and included static measures of starting and ending angles, and dynamic measures of midpoint, falltime, and lift speed. Control subjects completed significantly more lifts and lifted more weight than patients. Starting hip flexion was greater for controls and starting knee flexion was greater for patients, indicating that patients used more of a leg lift. Patients and controls also differed significantly on dynamic measures, particularly lifting speed and hip and knee temporal midpoints. Major static and dynamic motion differences were found between LBP patients and controls as they performed repetitive lifting under a constant load. These findings indicate that body motion parameters, in addition to more common strength and endurance measures, are necessary to describe the impact of persistent LBP on a person's lifting abilities.

Sensitivity of patients with painful temporomandibular disorders to experimentally evoked pain: evidence for altered temporal summation of pain

Temporomandibular disorders (TMD) represent a group of chronic painful conditions involving the muscles of mastication and the temporomandibular joint. Several studies have reported that TMD is associated with enhanced sensitivity to experimental pain. Twenty-three TMD subjects and 24 pain-free matched control subjects participated in a set of studies which were designed to evaluate whether the temporal integrative aspects of thermal pain perception are altered in TMD patients compared with control subjects. Specifically, we have examined in both TMD patients and in age- and gender-matched control subjects: (1) the time-course and magnitude of perceived pain evoked by the application of sustained 7-s noxious thermal stimuli (45–48°C) to the face and forearm, (2) the central summation of C-fiber-mediated pain produced by applying brief trains of noxious heat pulses to the skin overlying the ventral aspect of the right palm and (3) the ability to discriminate small increments in noxious heat applied to facial and volar forearm skin. Data collected from these studies indicate that TMD patients show enhanced temporal integration of thermal pain compared with control subjects. TMD patients show greater thermal C-fiber-mediated temporal summation than pain-free subjects and they report a greater magnitude of sustained noxious heat pulses applied to either the face or the forearm than control subjects. In contrast to these findings, TMD and pain-free subjects are equally able to discriminate and detect small increments of heat applied to noxious adapting temperatures. These findings suggest that the augmented temporal integration of noxious stimuli may result from alterations in central nervous system processes which contribute to the enhanced pain sensitivity observed in TMD patients.

Vibrotactile amplitude and frequency discrimination in temporomandibular disorders

The purpose of this study was to determine whether the elevation in vibrotactile detection threshold, found in many individuals with temporomandibular disorders (TMD), is paralleled by suprathreshold impairments. Participants with TMD were compared with pain-free control subjects in their ability to discriminate on the basis of differences in amplitude and frequency between vibratory stimuli delivered to the face. The TMD group was significantly impaired with respect to frequency discrimination, but not amplitude discrimination. This dissociation suggests that the cortical processing of vibrotactile signals may be affected in TMD patients. TMD participants' estimates of the intensity of their spontaneous and palpation-evoked pain did not significantly correlate with performance on either discrimination task; this finding makes it unlikely that impaired vibrotaction in TMD is primarily the result of a pain-dependent gating of tactile signals.

Fibromyalgia as a disorder of perceptual organization? An analysis of acoustic stimulus processing in patients with widespread pain.

We examined to what extent patients with fibromyalgia differ from painfree control subjects in the perception and processing not only of somatosensory but also of external stimuli. For this purpose the acoustic perception of 30 patients with fibromyalgia was compared with that of 36 generally pain-free age and gender matched subjects. The groups were also controlled for organic disease of pathological dysfunction of the ear and auditory nerves. Thresholds of unpleasantness and hearing thresholds were determined autiometrically for various frequencies. In addition the participants rated their experience of daily noise, vulnerability to acoustic stress, and functional and affective complaints associated with fibromyalgia. As expected the results show reduced unpleasantness thresholds for all frequencies and a nonsymptomatic hearing loss for higher frequencies. The elevated hearing threshold correlated significantly with experience of noise at the place of work, which was also elevated in the fibromyalgia group. Generalized pain had a high impact on the interaction between threshold of unpleasantness and daily noise experience. We interpret the differences in thresholds of hearing and of unpleasantness in patients with fibromyalgia as a form of either preconscious or conscious acts to protect against disturbing stimulation. Our results support the notion of a generalized disturbancy of perceptual thresholds in patients with fibromyalgia not restricted to the perception of pain.

Nuclear magnetic resonance spectroscopy of cerebrospinal fluid from patients with low back pain and sciatica.

This study was carried out to assess the metabolic differences between pain-free control subjects and patients with low back pain, either with or without disc protrusion or herniation. To analyze various metabolites in human cerebrospinal fluid using proton nuclear magnetic resonance spectroscopy. The potential use of this technique as an additional tool for diagnostic assessment was also evaluated. Inflammation is thought to play a major role in the generation of lumbar spine pain, a theory supported both by animal and in vitro studies. The effect of the inflammation in terms of increased metabolism has not yet been studied. Cerebrospinal fluid was obtained from patients by lumbar puncture, frozen, redissolved, and analyzed for metabolites by proton nuclear magnetic resonance spectroscopy. Significantly lower values for several key metabolites were found in patients with low back pain or sciatica, with the lowest values in the subgroup of patients with myelographic signs of disc protrusion or herniation. The results indicate a higher level of metabolic activity in patients with low back pain or sciatica compared with pain-free control subjects, with this difference being most pronounced in the subgroup of patients with myelographic evidence of disc protrusion or herniation.

Correlation of objective measure of trunk motion and muscle function with low-back disability ratings.

A study was undertaken to examine relations among some objective and subjective measures of low-back-related disability in a group of 41 low-back pain patients and in seven pain-free control subjects. Subjective measures of disability were obtained by Oswestry patient questionnaires. Oswestry disability score related significantly (P less than 0.001) to presence or absence of relaxation in back muscles during flexion. Mean trunk strength ratios were inversely related to disability score (P less than .05), and trunk mobility was meaningfully reduced (P less than .01). Despite loss of motion, a large enough excursion was observed to predict presence of back muscle relaxation. These findings imply that myoelectric signal levels, trunk strength ratios, and ranges of trunk motion may be used as objective indicators of low-back pain disability.

Combined Use of Experimental Pain and Visual Analogue Scales in Providing Standardized Measurement of Clinical Pain

Myofascial pain dysfunction (MPD) patients, pain-free control subjects, and low back patients from a previous study were compared for visual analogue scale (VAS) responses to experimental pain (43–51°C temperatures) and clinical pain. MPD, low back pain, and control groups' nociceptive temperature-VAS response functions were all power functions with exponents of 2.1 for VAS-sensory-intensity responses, and 2.4–2.7 for VAS-affective responses. MPD patients' VAS-sensory responses to clinical pain, direct temperature matches to clinical pain, and temperature-VAS response function were internally consistent. The similar nociceptive stimulus-VAS response functions and consistent use of VAS to rate experimental and clinical pain provide a standardized procedure, whereby intensities of different types of pain can be accurately compared.

Estimation of time as a measure of pain magnitude.

A new method of measuring pain is presented where the patient's estimation of time is used as a pain-related parameter. Pain patients experience a certain time period as increased when compared with pain free control subjects. The increase in time estimation correlates roughly with the clinical estimate of pain severity in different diagnostic groups. Successfully treated patients change their time estimation towards normal. It is considered that this method could be used to evaluate a certain patient's pain and the effectiveness of treatment in relation to the mean time estimate of other patients with the same diagnosis.

INCREASED β-ENDORPHIN BUT NOT MET-ENKEPHALIN LEVELS IN HUMAN CEREBROSPINAL FLUID AFTER ACUPUNCTURE FOR RECURRENT PAIN

Low-frequency electroacupuncture effectively alleviated recurrent pain in 10 patients. Basal levels of β-endorphin and met-enkephalin in the lumbar cerebrospinal fluid (CSF) of these patients were not different from those in pain-free control subjects. After electroacupuncture in the patients with pain CSF β-endorphin levels rose significantly in all subjects, but met-enkephalin levels were unchanged. These results suggest that the analgesia observed after electroacupuncture in patients with recurrent pain may be mediated by the release into the CSF of the endogenous opiate, β-endorphin.