The journal of pain : official journal of the American Pain Society
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Comparative Study
Factors associated with depressed mood in chronic pain patients: the role of intrapersonal coping resources.
The purpose of this study was to examine processes through which chronic pain can result in depressed mood and to determine whether intrapersonal coping resources, namely high self-esteem and optimism, affect these processes. We hypothesized that pain severity contributes to depressed mood largely because pain interferes with involvement in important pursuits. We then examined whether intrapersonal resources are directly associated with pain severity, interference, and depressed mood and whether resources moderate associations between pain and interference or between interference and depressed mood. Structured interviews containing psychometrically robust measures were conducted with 141 outpatients of a university hospital-affiliated chronic pain center. As predicted, interference mediated much of the association between pain severity and depressed mood, and high resources were associated with less severe pain, less interference, and lower depressed mood. The association between pain severity and interference was stronger for people with high than people with low intrapersonal resources. The pattern of results that emerged from this study illustrates that intrapersonal coping resources may affect chronic pain patients through a variety of differentiated mechanisms. Pain severity appears to have greater adverse impact on the activity of people who possess highly positive self-views and outlook, but these resources are also associated with better emotional status. ⋯ Pain had greater adverse impact on the activity of people with highly positive self-views and outlook, but these coping resources were also associated with better emotional status. Chronic pain sufferers with few resources may require different interventions than those with more positive views of themselves and the world around them.
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This study evaluated sensory and biomechanical assets in 2 heel pain conditions with similar symptoms, entrapment syndrome of the nerve to abductor digiti quinti and myofascial syndrome of abductor hallucis. Thirty-three patients with unilateral heel pain and 20 asymptomatic subjects underwent pressure pain threshold measurement in the painful area in site A (medial process of calcaneal tuberosity, trigger point site of abductor hallucis) and site B (1 cm posteriorly to site A, where the nerve to abductor digiti quinti becomes most superficial) and contralaterally; electroneurography of posterior tibial nerve; evaluation of ground-foot reaction on a dynamic platform. Eighteen patients had electric shock-type pain (entrapment syndrome, Group 1), 15 had cramp-like pain (myofascial syndrome, Group 2). Pain thresholds on the affected side versus contralaterally were significantly lower in site B in Group 1 and in site A in Group 2 (P < .001). Nerve conduction velocity was slightly reduced in Group 1 (P = .05). Ground-foot reaction was significantly altered on the affected side in all patients versus asymptomatic subjects; a significant difference between the 2 sides was found for peak of force (F1) in Group 1 and for all parameters except temporal phase of peak of force (TF3) (P = .05) for Group 2 (P < .0001). The different sensory and biomechanical patterns of the 2 examined syndromes help the differential diagnosis and consequent therapeutic approach. ⋯ This study shows different sensory and biomechanical patterns in 2 algogenic conditions of the heel with similar pain location. These distinct patterns reflect different pathophysiologic mechanisms in the 2 cases, which has a potential significant impact on treatment.
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Transcutaneous electrical nerve stimulation (TENS) is a nonpharmacological method for pain management. Commercial TENS units differ in their waveform characteristics. However, effects of different waveforms on analgesia produced by TENS are unknown. Therefore, we compared effects of high-frequency TENS with different waveforms--asymmetric biphasic square and symmetric biphasic square--on inflammatory hyperalgesia. Paw withdrawal latency to heat (PWL) was assessed prior to inflaming the knee joint with 3% carrageenan/kaolin in rats. Four hours after induction of inflammation, PWL significantly decreased in all groups, indicating development of hyperalgesia. High-frequency TENS was then applied to the inflamed knee joint for 20 minutes while the rat was lightly anesthetized with halothane. TENS treatment with either the asymmetric or symmetric waveform significantly increased the PWL when compared with sham TENS. Thus, differences in waveform characteristics do not affect the anti-hyperalgesia produced by TENS. ⋯ This study shows that different waveforms of TENS do not affect analgesic efficacy. This suggests that clinicians can select different waveforms to provide comfort during treatment but that reduction in pain is not a factor for waveform selection.