The journal of pain : official journal of the American Pain Society
-
The present study examined whether pain catastrophizing and pain-related fear predict the experience of pain in body regions that are not targeted by an experimental muscle injury protocol. A delayed-onset muscle soreness (DOMS) protocol was used to induce pain unilaterally in the pectoralis, serratus, trapezius, latissimus dorsi, and deltoid muscles. The day after the DOMS protocol, participants were asked to rate their pain as they lifted weighted canisters with their targeted (ie, injured) arm and their nontargeted arm. The lifting task is a nonnoxious stimulus unless participants are already experiencing musculoskeletal pain. Therefore, reports of pain on the nontargeted arm were operationalized as pain in response to a nonnoxious stimulus. Eighty-two healthy university students (54 men, 28 women) completed questionnaires on pain catastrophizing and fear of pain and went through the DOMS protocol. The analyses revealed that catastrophizing and pain-related fear prospectively predicted pain experience in response to a nonnoxious stimulus. The possible mechanisms underlying this effect and clinical implications are discussed. ⋯ Pain catastrophizing and fear of pain prospectively predict the pain experience in response to a nonnoxious stimulus. The pattern of findings is consistent with the predictions of current models of generalization of pain-related fear.
-
Interactions between exogenous and endogenous opioids are not commonly investigated as a basis for sexually dimorphic opioid analgesia. We investigated the influence of spinal endomorphin 2 (EM2), an endogenous mu-opioid receptor (MOR) ligand, on the spinal antinociception produced by intrathecally administered opioids. Activation of spinal MORs facilitated spinal EM2 release. This effect was sexually dimorphic, occurring in males but not in females. Although activational effects of testosterone were required for opioid facilitation of spinal EM2 release in males, the absence of this facilitation in females did not result from either insufficient levels of testosterone or mitigating effects of estrogens. Strikingly, in males, the contribution of spinal EM2 to the analgesia produced by intrathecally applied MOR agonists depended on their analgesic efficacy relative to that of EM2. Spinal EM2 released by the higher efficacy MOR agonist sufentanil diminished sufentanil's analgesic effect, whereas EM2 released by the lower efficacy morphine had the opposite effect on spinal morphine antinociception. Understanding antithetical contributions of endogenous EM2 to intrathecal opioid antinociception not only enlightens the selection of opioid medications for pain management but also helps to explain variable sex dependence of the antinociception produced by different opioids, facilitating the acceptance of sexually dimorphic antinociception as a basic tenet. ⋯ The male-specific MOR-coupled enhancement of spinal EM2 release implies a parallel ability to harness endogenous EM2 antinociception. The inferred diminished ability of females to utilize the spinal EM2 antinociceptive system could contribute to their greater frequency and severity of chronic pain syndromes.
-
Familial amyloid polyneuropathy (FAP) caused by transthyretin (TTR) mutation is a small-fiber predominant polyneuropathy, exposing patients with TTR-FAP to development of neuropathic pain. However, the painful nature of TTR-FAP has never been specifically addressed. In this study, we compared 2 groups of 16 patients with either painless or painful TTR-FAP with regard to various clinical and neurophysiologic variables, including laser evoked potential (LEP) recording and quantitative sensory testing. The 2 groups of patients did not differ on any clinical or neurophysiologic variable. Patients with painful TTR-FAP complained of ongoing burning pain sensations, pain aggravation at rest, paroxysmal pain (electric shock and stabbing sensations), or provoked pain (mostly dynamic mechanical allodynia). However, the symptomatic presentation of painful TTR-FAP evolved with the course of the disease. The duration of the disease and the severity of small-fiber lesions (increase in thermal thresholds and reduction in LEP amplitude) correlated negatively with the intensity of ongoing burning sensations and positively with the intensity of paroxysmal pain. In addition, small-fiber preservation correlated positively with cold allodynia and pain aggravation at rest and negatively with dynamic mechanical allodynia. Peripheral sensitization of small-diameter nociceptive axons might occur in early TTR-FAP and be responsible for the burning sensation and cold allodynia. As polyneuropathy and small-fiber loss progress, paroxysmal pain and dynamic mechanical allodynia may develop as a result of central sensitization generated by abnormal activities affecting relatively spared large-diameter sensory fibers. ⋯ Pain in TTR-FAP includes several mechanisms varying with the course of the disease and the involvement of the different types of nerve fibers.
-
Randomized Controlled Trial Comparative Study
Manual Physical Therapy versus Surgery for Carpal Tunnel Syndrome: a Randomized Parallel-Group Trial.
This randomized clinical trial investigated the effectiveness of surgery compared with physical therapy consisting of manual therapies including desensitization maneuvers in carpal tunnel syndrome (CTS). The setting was a public hospital and 2 physical therapy practices in Madrid, Spain. One hundred twenty women with CTS were enrolled between February 2013 and January 2014, with 1-year follow-up completed in January 2015. Interventions consisted of 3 sessions of manual therapies including desensitization maneuvers of the central nervous system (physical therapy group, n = 60) or decompression/release of the carpal tunnel (surgical group, n = 60). The primary outcome was pain intensity (mean pain and the worst pain), and secondary outcomes included functional status and symptoms severity subscales of the Boston Carpal Tunnel Questionnaire and the self-perceived improvement. They were assessed at baseline and 1, 3, 6, and 12 months by a blinded assessor. Analysis was by intention to treat. At 12 months, 111 (92%) women completed the follow-up (55/60 physical therapy, 56/60 surgery). Adjusted analyses showed an advantage (all, P < .01) for physical therapy at 1 and 3 months in mean pain (Δ -2.0 [95% confidence interval (CI) -2.8 to -1.2]/-1.3 [95% CI -2.1 to -.6]), the worst pain (Δ -2.9 [-4.0 to -2.0]/-2.0 [-3.0 to -.9]), and function (Δ -.8 [-1.0 to -.6]/-.3 [-.5 to -.1]), respectively. Changes in pain and function were similar between the groups at 6 and 12 months. The 2 groups had similar improvements in the symptoms severity subscale of the Boston Carpal Tunnel Questionnaire at all follow-ups. In women with CTS, physical therapy may result in similar outcomes on pain and function to surgery.
-
Sickle cell disease (SCD) is a hemoglobinopathy that affects more than 100,000 individuals in the United States. The disease is characterized by the presence of sickle hemoglobin and recurrent episodes of pain. Some individuals with SCD experience frequent hospitalizations and a high burden of pain. The role of central mechanisms in SCD pain has not been explored. Twenty-five adolescents and young adults with SCD underwent functional magnetic resonance imaging. Participants were stratified into groups with high pain or low pain based on the number of hospitalizations for pain in the preceding 12 months. Resting state functional connectivity was analyzed using seed-based and dual regression independent component analysis. Intrinsic brain connectivity was compared between the high pain and low pain groups, and association with fetal hemoglobin, a known modifier of SCD, was explored. Patients in the high pain group displayed an excess of pronociceptive connectivity such as between anterior cingulate and default mode network structures, such as the precuneus, whereas patients in the low pain group showed more connectivity to antinociceptive structures such as the perigenual and subgenual cingulate. Although a similar proportion of patients in both groups reported that they were on hydroxyurea, the fetal hemoglobin levels were significantly higher in the low pain group and were associated with greater connectivity to antinociceptive structures. These findings support the role of central mechanisms in SCD pain. Intrinsic brain connectivity should be explored as a complementary and objective outcome measure in SCD pain research. ⋯ Altered connectivity patterns associated with high pain experience in patients with sickle cell disease suggest a possible role of central mechanisms in sickle cell pain. Resting state brain connectivity studies should be explored as an effective methodology to investigate pain in SCD.