The reliability and validity of functional brain connectivity compared to a self-reported measure of pain

Pain is a multidimensional perception that is complex in nature. It is a unitary construct that includes overlapping domains such as intensity, affect, quality, and frequency. These domains do not reflect the amount of tissue damage. It reflects the end result of the perception of pain in which multiple biopsychosocial factors are involved (Gatchel et al., 2007). Multiple self-reported measures have been used in an attempt to capture most factors that may influence pain such as psychological factors. However, there is no one scale that can be used to characterize pain as a whole with all its factors. Furthermore, physical measurements did not prove to be better than self-reported measure in pain characterization. Since pain perception is believed to occur in the brain, it seems rational to measure aspects of the brain as a biomarker for pain. One method that has been recently used is functional connectivity magnetic resonance imaging (fcMRI), which is a measure of the connectivity between brain regions that are previously known to be related to pain. In this paper the focus will be on the recent “physical measure” of pain in comparison to the self-reported measure, the Gracely box scale. First a summary of the reliability and validity of the Gracely box scale will be mentioned. Then the development of the functional connectivity based on the fMRI studies will be addressed. Finally, I will assess the reliability and validity of the measure compared to the Gracely box scale

The Impact of Isometric Exercise on Somatosensory Processing in People with or without Chronic Pain

Despite an increase in our understanding of the pathomechanisms of chronic pain and the advancement of new treatments, pharmacological management of chronic pain remains poor. This presents the need for non-pharmacological treatments and understanding their efficacy and mechanisms in managing pain. The purpose of this dissertation was to examine the effects of isometric exercise on the somatosensory system and other biopsychosocial aspects related to pain in individuals with and without fibromyalgia. The first aim was to determine whether isometric exercise improves pain inhibitory mechanisms and vibration sense. The second aim was to determine what biopsychosocial factors influence pain relief following exercise.In study one, conditioned pain modulation (CPM; a measure of pain inhibitory mechanism) was assessed before and after exercise (submaximal isometric contraction of the knee extensors held for three minutes) and quiet rest in young healthy adults. In study two, CPM and vibration sense were assessed before and after exercise (submaximal isometric contraction of the knee extensors held until exhaustion) and quiet rest in individuals with and without fibromyalgia. In both studies, the influence of biopsychosocial factors (e.g. body composition, physical activity, pain catastrophizing, kinesiophobia, and pain self-efficacy) were assessed. In study one, local hypoalgesia occurred at the exercising muscle while systemic hypoalgesia was much more variable. CPM decreased at the upper trapezius following exercise in those individuals that reported systemic hypoalgesia and was unchanged in those without systemic hypoalgesia. In study two, local and systemic hypoalgesia occurred with exercise. CPM increased at the deltoid following exercise only in those individuals with impaired baseline CPM irrespective of health status (healthy control or fibromyalgia). Vibration sense increased at a site distal from the exercising muscle (i.e. the index finger). Additionally, pain relief following exercise was not influenced by body composition physical activity, kinesiophobia, and pain self-efficacy. The results from these studies suggest that CPM and systemic exercise-induced hypoalgesia may have similar mechanisms, and the biopsychosocial factors measured in these studies did not impact the pain relief following exercise. Thus, exercise may be a good modality to restore descending pain inhibition and improve vibratory sense

Systemic Exercise-Induced Hypoalgesia Following Isometric Exercise Reduces Conditioned Pain Modulation

Objective Physically active individuals show greater conditioned pain modulation (CPM) compared with less active individuals. Understanding the effects of acute exercise on CPM may allow for a more targeted use of exercise in the management of pain. This study investigated the effects of acute isometric exercise on CPM. In addition, the between-session and within-session reliability of CPM was investigated. Design Experimental, randomized crossover study. Setting Laboratory at Marquette University. Subjects Thirty healthy adults (19.3±1.5 years, 15 males). Methods Subjects underwent CPM testing before and after isometric exercise (knee extension, 30% maximum voluntary contraction for three minutes) and quiet rest in two separate experimental sessions. Pressure pain thresholds (PPTs) at the quadriceps and upper trapezius muscles were assessed before, during, and after ice water immersions. Results PPTs increased during ice water immersion (i.e., CPM), and quadriceps PPT increased after exercise (P \u3c 0.05). CPM decreased similarly following exercise and quiet rest (P \u3e 0.05). CPM within-session reliability was fair to good (intraclass correlation coefficient [ICC] = 0.43–0.70), and the between-session reliability was poor (ICC = 0.20–0.35). Due to the variability in the systemic exercise-induced hypoalgesia (EIH) response, participants were divided into systemic EIH responders (N = 9) and nonresponders (N = 21). EIH responders experienced attenuated CPM following exercise (P = 0.03), whereas the nonresponders showed no significant change (P \u3e 0.05). Conclusions Isometric exercise decreased CPM in individuals who reported systemic EIH, suggesting activation of shared mechanisms between CPM and systemic EIH responses. These results may improve the understanding of increased pain after exercise in patients with chronic pain and potentially attenuated CPM

Hypoesthesia in Knee Osteoarthritis: Relationship of Pain, Vibration Perception and Proprioception

Purpose: Hypoesthesia, or partial loss of sensitivity to sensory stimuli has been reported in individuals with knee osteoarthritis (OA), with deficits reported in both proprioception (kinesthesia and repositioning) and vibration perception threshold (VPT) at the affected knee. The mechanisms underlying these deficits are unclear, however, previous evidence has indicated that diminished somatosensation, such as VPT may occur due to altered nociceptive processing. It has been postulated that similar mechanisms may explain deficits in kinesthesia, or the ability to detect passive joint movement in knee OA, however this premise has not been examined. It was hypothesized in this study that deficits in VPT and proprioception (kinesthesia) would be associated in subjects with knee OA. The purpose of this study was to explore the relationship between somatosensory measures of pain, vibration detection, proprioception and function in persons with knee OA. Methods: Fifteen individuals (mean age, 55.6±7.4y; 8 female; BMI 32.0±7) diagnosed with OA of the tibiofemoral joint by their physician (≥ grade II Kellgren and Lawrence radiographic changes) participated. Measurements included VPT at the knee using a biothesiometer, proprioception tested via threshold to detection of passive movement, resting and worst pain during the week prior to testing examined via Numeric Pain Rating Scale (NPRS), function using the Knee Outcome Survey Activities of Daily Living Scale (KOS) and isometric quadriceps strength. Results: Subjects reported resting pain (3.1±3.0) and worst pain (6.2±2.6) on the NPRS, and 56±16% on the KOS, indicating an average of 50% deficit in function. Quadriceps strength, vibration perception and proprioception were significantly different between limbs (p<0.05). These deficits were not correlated (r=.02) however a moderate correlation was found between proprioception deficits and resting and worst pain (r=.54, p<0.05), but not with vibration. No correlation was found between diminished function as measured by the KOS and both vibratory and proprioceptive deficits. Conclusions: Hypoesthesia, as measured by proprioception and vibration detection was significantly impaired on the painful OA limb compared to the contralateral limb and these findings were correlated to resting and worst pain. Functional deficits were only weakly correlated to somatosensory deficits, indicating that diminished function is likely multifactorial in nature

Lean mass mediates the relation between temporal summation of pain and sex in young healthy adults

Abstract Background Previous studies have shown that women experience greater temporal summation (TS) of pain than men using a repetitive thermal stimulus. These studies, however, did not individualize the thermal stimulus to each subject’s thermal pain sensitivity. The aim of this study was to investigate sex differences in TS using an individualized protocol and potential mediators that have been shown to influence TS including physical activity and body composition. Methods Fifty young healthy men and women (21 men) participated in the study. Subjects completed TS testing on the right forearm using a repetitive thermal stimulus at a temperature that the subject reported 6/10 pain. Other testing included body composition (lunar iDXA), activity monitoring (Actigraph), and Pain Catastrophizing Scale (PCS). Results Women reported greater TS than men (p = 0.019), and TS was correlated with right arm lean mass (r = − 0.36, p = 0.01) and magnification subscale of PCS (r = − 0.32, p = 0.03). Mediation analysis showed a complete mediation for the relation between sex and TS by right arm lean mass (indirect effect = 2.33, 95% BCa CI [0.42, 4.58]) after controlling for the temperature, the magnification subscale of PCS, and the average time spent in moderate to vigorous physical activity. Conclusion The results of this study suggest that lean mass is a contributing factor to the sex differences in TS. Future studies should investigate whether interventions that increase lean mass have a positive effect on TS

Moving Beyond the Neck and Arm: The Pain Experience of People With Degenerative Cervical Myelopathy Who Have Pain.

STUDY DESIGN: Cross-sectional internet survey of people living with degenerative cervical myelopathy. OBJECTIVE: The purpose of this study was to quantify pain distribution, severity, and interference in persons with degenerative cervical myelopathy. METHODS: Eighty-two participants with degenerative cervical myelopathy were recruited for this internet survey. This survey utilized the Michigan Body Map and brief pain inventory (BPI) to assess anatomical distribution and severity of pain as well as the patient derived modified Japanese Orthopedic Association scale (p-mJOA) for myelopathic severity and SF-36 for measures of health-related quality of life. Internal consistency was evaluated with Cronbach's alpha. Pearson's correlations were assessed with p-mJOA and SF-36. Multivariate analysis of variance was used to determine if history of prior surgery or concomitant pain diagnosis impacted experience of pain. RESULTS: Michigan body map distribution and brief pain inventory severity and interference were correlated with p-mJOA and SF-36 scores (p 0.9). History of surgery or other pain diagnosis did not impact experience of pain in myelopathy. CONCLUSIONS: Pain is commonly identifiable in large areas of the body, is frequently moderate to severe in intensity and impacts quality of life and severity of myelopathy in a cohort of individuals with myelopathy who have pain