The journal of pain : official journal of the American Pain Society
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Little is known about endogenous descending control of itch. In chronic pain, descending pain inhibition is reduced as signified by lowered conditioned pain modulation. There are indications that patients with chronic itch may also exhibit reduced endogenous descending inhibition of itch and pain. ⋯ Itch was significantly reduced (conditioned itch modulation-effect) by contra- as well as ipsilateral applied conditioning pain (both P < .001), whereas conditioning itch stimulation only marginally reduced itch. Endogenous descending itch inhibition through mechanisms that are independent of segmental gating can be readily evoked by heterotopic conditioning pain stimulation. However, robust descending inhibition of itch cannot be evoked with conditioning itch stimulation.
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Randomized Controlled Trial Comparative Study
Comparison of two lumbar manual therapies on temporal summation of pain in healthy volunteers.
The purpose of this study was to compare the immediate change in temporal summation of heat pain (TSP) between spinal manipulation (SMT) and spinal mobilization (MOB) in healthy volunteers. Ninety-two volunteers (24 male; 23.8 ± 5.3 years) were randomized to receive SMT, MOB, or no treatment (REST) for 1 session. Primary outcomes were changes in TSP, measured at the hand and foot, immediately after the session. A planned subgroup analysis investigated effects across empirically derived TSP clusters. For the primary outcome there were no differences in the immediate change in TSP measured at the foot between SMT and MOB, however, both treatments were superior to the REST condition. In the subgroup analysis the response to a standard TSP protocol was best characterized by 3 clusters: 52% no change (n = 48, 52%); facilitatory response (n = 24, 26%), and inhibitory response (n = 20, 22%). There was a significant Time × Treatment group × Cluster interaction for TSP measured at the foot. The inhibitory cluster showed the greatest attenuation of TSP after SMT and MOB compared with REST. These data suggest lumbar manual therapies of different velocities produce a similar localized attenuation of TSP, compared with no treatment. Attenuation of localized pain facilitatory processes by manual therapies was greatest in pain-free individuals who show an inhibitory TSP response. ⋯ The attenuation of pain facilitatory measures may serve an important underlying role in the therapeutic response to manual therapies. Identifying patients in pain who still have an inhibitory capacity (ie, an inhibitory response subgroup) may be useful clinically in identifying the elusive "manual therapy" responder.
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Randomized Controlled Trial
Explicit education about exercise-induced hypoalgesia influences pain responses to acute exercise in healthy adults: A randomised controlled trial.
The mechanisms through which acute exercise reduces pain (ie, exercise-induced hypoalgesia [EIH]) are poorly understood. This study aimed to determine if education about EIH affected pain responses after acute exercise in healthy adults. Participants received 15 minutes of education either about EIH (intervention, n = 20) or more general education about exercise and pain (control, n = 20). ⋯ Compared with the control group, the intervention group believed more strongly that pain could be reduced by a single session of exercise (P = .005) and that the information they had just received had changed what they thought about the effect of exercise on pain (P = .045). After exercise, pressure pain threshold increased in both groups, but the median increase was greater in the intervention group compared with the control group (intervention = .78 kg/cm2, control = .24 kg/cm2, P = .002, effect size [r] of difference = .49). These results suggest that cognitive processes in the appraisal of pain can be manipulated to influence EIH in healthy adults.
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The relationships between the initial opioid prescription characteristics and pain etiology with the probability of opioid discontinuation were explored in this retrospective cohort study using health insurance claims data from a nationally representative database of commercially insured patients in the United States. We identified 1,353,902 persons aged 14 years and older with no history of cancer or substance abuse, with new opioid use episodes and categorized them into 11 mutually exclusive pain etiologies. Cox proportional hazards models were estimated to identify factors associated with time to opioid discontinuation. ⋯ Increasing days' supply of the first prescription was consistently associated with a lower likelihood of opioid discontinuation (HRs, CIs: 3-4 days' supply = .70, .70-.71; 5-7 days' supply = .48, .47-.48; 8-10 days' supply = .37, .37-.38; 11-14 days' supply = .32, .31-.33; 15-21 days' supply = .29, .28-.29; ≥22 days supplied = .20, .19-.20). The direction of this relationship was consistent across all pain etiologies. Clinicians should initiate patients with the lowest supply of opioids to mitigate unintentional long-term opioid use.
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This systematic review synthesizes literature describing prevalence, characteristics, and prognosis of low back-related leg pain (LBLP) patients with neuropathic pain in primary care and/or similar settings. Inclusion and exclusion criteria were developed and used by independent reviewers to screen citations for eligibility. The initial search yielded 24,948 citations; after screening 12 studies were included. Neuropathic pain was identified using case ascertainment tools (n = 5), clinical history with examination (n = 4), and using LBLP samples assumed neuropathic (n = 3). Neuropathic pain prevalence varied from 19% to 80%. There was consistent evidence for higher back-related disability (n = 3), poorer health-related quality of life (n = 2), and some evidence for more severe depression (n = 2), anxiety (n = 3), and pain intensity (n = 4) in patients with neuropathic pain. Results were less consistent when cases were identified through clinical history with examination than those identified using case ascertainment tools. Prognosis (n = 1) of LBLP patients with neuropathic pain was worse compared with those without, in all outcomes (leg pain intensity, leg and back-related disability, self-reported general health) except back pain intensity. No studies described prognostic factors. This systematic review highlights the evidence gap in neuropathic pain in LBLP in primary care, especially with respect to prognosis. ⋯ Patients with LBLP may have neuropathic pain. This systematic review emphasizes the paucity of evidence describing the characteristics and prognosis of neuropathic pain in this patient population. Future research investigating prognosis of these patients with neuropathic pain is likely to contribute to better understanding and management.