The journal of pain : official journal of the American Pain Society
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Persistent pain following breast cancer surgery is well documented. However, it is not well characterized in terms of the anatomic site affected (ie, breast, arm). In 2 separate growth mixture modeling analyses, we identified subgroups of women (N = 398) with distinct breast pain and arm pain trajectories. The fact that these latent classes differed by anatomic site, types of tissue affected, and neural innervation patterns suggests the need for separate evaluations of these distinct persistent pain conditions. The purposes of this companion study were to identify demographic and clinical characteristics that differed between the 2 arm pain classes and determine if differences existed over time in sensitivity in the upper inner arm and axillary lymph node dissection sites, pain qualities, pain interference, and hand and arm function, as well as to compare findings with persistent breast pain. Higher occurrence rates for depression and lymphedema were found in the moderate arm pain class. Regardless of pain group membership, sensory loss was observed in the upper inner arm and axillary lymph node dissection site. Arm pain was described similarly to neuropathic pain and interfered with daily functioning. Persistent arm pain was associated with sustained impairments in shoulder mobility. ⋯ For persistent breast and arm pain, changes in sensation following breast cancer surgery were notable. Persistent arm pain was associated with sustained interference with daily functioning and upper body mobility impairments. Long-term management of persistent pain following breast cancer surgery is warranted to improve the quality of survivorship for these women.
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Interindividual variability exists in persistent breast pain following breast cancer surgery. Recently, we used growth mixture modeling to identify 3 subgroups of women (N = 398) with distinct persistent breast pain trajectories (ie, mild, moderate, severe) over 6 months following surgery. The purposes of this study were to identify demographic and clinical characteristics that differed among the breast pain classes and, using linear mixed effects modeling, to examine how changes over time and in sensitivity in the breast scar area, pain qualities, pain interference, and hand and arm function differed among these classes. Several demographic and clinical characteristics differentiated the breast pain classes. Of note, 60 to 80% of breast scar sites tested were much less sensitive than the unaffected breast. Significant group effects were observed for pain qualities and interference scores, such that, on average, women in the severe pain class reported higher scores than women in the moderate pain class. In addition, women in the moderate pain class reported higher scores than women in the mild pain class. Compared to women in the mild pain class, women in the severe pain class had significantly impaired grip strength, and women in the moderate and severe pain classes had impaired flexion and abduction. ⋯ Subgroups of women with persistent postsurgical breast pain differed primarily with respect to the severity rather than the nature or underlying mechanisms of breast pain. Pervasive sensory loss and the association between persistent breast pain and sustained interference with function suggest the need for long-term clinical follow-up.
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The purpose of this study was to examine opioid and endocannabinoid mechanisms of exercise-induced hypoalgesia (EIH). Fifty-eight men and women (mean age = 21 years) completed 3 sessions. During the first session, participants were familiarized with the temporal summation of heat pain and pressure pain protocols. In the exercise sessions, following double-blind administration of either an opioid antagonist (50 mg naltrexone) or placebo, participants rated the intensity of heat pulses and indicated their pressure pain thresholds and pressure pain ratings before and after 3 minutes of submaximal isometric exercise. Blood was drawn before and after exercise. Results indicated that circulating concentrations of 2 endocannabinoids, N-arachidonylethanolamine and 2-arachidonoylglycerol, as well as related lipids oleoylethanolamide, palmitoylethanolamide, N-docosahexaenoylethanolamine, and 2-oleoylglycerol, increased significantly (P < .05) following exercise. Pressure pain thresholds increased significantly (P < .05), whereas pressure pain ratings decreased significantly (P < .05) following exercise. Also, temporal summation ratings were significantly lower (P < .05) following exercise. These changes in pain responses did not differ between the placebo and naltrexone conditions (P > .05). A significant association was found between EIH and docosahexaenoylethanolamine. These results suggest involvement of a nonopioid mechanism in EIH following isometric exercise. ⋯ Currently, the mechanisms responsible for EIH are unknown. This study provides support for a potential endocannabinoid mechanism of EIH following isometric exercise.
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Randomized Controlled Trial Multicenter Study
Lenalidomide for complex regional pain syndrome type 1: lack of efficacy in a phase II randomized study.
Complex regional pain syndrome (CRPS) is a potentially debilitating chronic pain syndrome with a poorly understood but likely neuroimmune/multifactorial pathophysiology associated with axonal injury. Based on the potential contribution of proinflammatory cytokines to CRPS pathogenesis and prior research with thalidomide, we investigated lenalidomide, a thalidomide derivative, for CRPS treatment. We conducted a phase II, randomized, double-blind, placebo-controlled study to evaluate the efficacy of oral lenalidomide 10 mg once daily in consenting patients with unilateral or bilateral CRPS type 1. The study comprised 12 weeks of treatment followed by a long-term extension. The primary efficacy outcome was reduced pain in the index limb, defined as ≥30% improvement from baseline using an 11-point numeric rating scale. One hundred eighty-four subjects enrolled. The primary endpoint was not met because equal proportions of treated (16.1%) and control (16.1%) subjects achieved the outcome; however, lenalidomide was well tolerated, with no evidence of neuropathy or major adverse effects. This study is the largest controlled, blinded clinical trial in subjects with chronic CRPS using the Budapest research criteria. It demonstrates the feasibility of conducting high-quality clinical trials in CRPS type 1 and provides considerations for designing future trials. ⋯ This article reports an adequately powered, controlled clinical trial in subjects with CRPS. Treatment and placebo were equally effective, but the study demonstrated that lenalidomide treatment is feasible in this population. The study provides examples to consider in designing future CRPS trials.
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Randomized Controlled Trial
Repetitive transcranial magnetic stimulation of the left premotor/dorsolateral prefrontal cortex does not have analgesic effect on central poststroke pain.
Central poststroke pain (CPSP) is caused by an encephalic vascular lesion of the somatosensory pathways and is commonly refractory to current pharmacologic treatments. Repetitive transcranial magnetic stimulation (rTMS) of the premotor cortex/dorsolateral prefrontal cortex (PMC/DLPFC) can change thermal pain threshold toward analgesia in healthy subjects and has analgesic effects in acute postoperative pain as well as in fibromyalgia patients. However, its effect on neuropathic pain and in CPSP, in particular, has not been assessed. The aim of this prospective, double-blind, placebo-controlled study was to evaluate the analgesic effect of PMC/DLPFC rTMS in CPSP patients. Patients were randomized into 2 groups, active (a-) rTMS and sham (s-) rTMS, and were treated with 10 daily sessions of rTMS over the left PMC/DLPFC (10 Hz, 1,250 pulses/d). Outcomes were assessed at baseline, during the stimulation phase, and at 1, 2, and 4 weeks after the last stimulation. The main outcome was pain intensity changes measured by the visual analog scale on the last stimulation day compared to baseline. Interim analysis was scheduled when the first half of the patients completed the study. The study was terminated because of a significant lack of efficacy of the active arm after 21 patients completed the whole treatment and follow-up phases. rTMS of the left PMC/DLPFC did not improve pain in CPSP. ⋯ The aim of this double-blind, placebo-controlled study was to evaluate the analgesic effects of rTMS to the PMC/DLPFC in CPSP patients. An interim analysis showed a consistent lack of analgesic effect, and the study was terminated. rTMS of the PMC/DLPFC is not effective in relieving CPSP.