Pain
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Clinical Trial
The relationship of adult attachment to emotion, catastrophizing, control, threshold and tolerance, in experimentally-induced pain.
Although insecure attachment has been associated with a range of variables linked with problematic adjustment to chronic pain, the causal direction of these relationships remains unclear. Adult attachment style is, theoretically, developmentally antecedent to cognitions, emotions and behaviours (and might therefore be expected to contribute to maladjustment). It can also be argued, however, that the experience of chronic pain increases attachment insecurity. ⋯ Of particular interest were findings that attachment style moderated the effects of pain intensity on the tendency to catastrophize, such that insecurely attached individuals were more likely to catastrophize when reporting high pain intensity. This is the first study to link attachment with perceptions of pain in a pain-free sample. These findings cast anxious attachment as a vulnerability factor for chronic pain following acute episodes of pain, while secure attachment may provide more resilience.
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The sensitivity of tendon and tendon-bone junction is not fully described although these tissues have high clinical impacts. This study assessed (1) pain intensity and referred pain caused by hypertonic saline injection to the proximal tendon-bone junction (PTBJ), tendon and muscle belly sites of tibialis anterior muscle and (2) pressure pain sensitivity, pre, during and post hypertonic saline injections. Eighteen subjects (14 males and 4 females) participated. ⋯ Hypertonic saline pain at the tendon and PTBJ caused significantly higher (P < 0.001) final VAS scores compared to the muscle belly site. The results indicate the PTBJ and tendon sites are more sensitive and susceptible to sensitisation by hypertonic saline than muscle belly. Furthermore, there may be site specific central changes reflected by the differences in the results regarding sensitivity and summation over time.
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Cold allodynia is a common complaint in patients with peripheral neuropathies. However, cold sensitivity of the different types of sensory afferents present in injured nerves is poorly known. We recorded activity evoked by cold in intact sensory fibers of the skin-saphenous nerve preparation and in axotomized sensory fibers of approximately 21 days-old neuromas of the saphenous nerve of mice, in vitro. ⋯ In conclusion, the transducing capacity to cold stimuli is substantially recovered in neuromas. Furthermore, axotomized fibers maintain the 4-AP-sensitive, voltage-activated, transient potassium conductance that counteracts the depolarizing effects of cold in the majority of intact, cold-insensitive primary afferents. Our results indicate that injured nociceptors do not develop abnormal cold sensitivity, suggesting that other mechanisms underlie the cold-induced allodynia following peripheral nerve injury.
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Randomized Controlled Trial
Characterizing individual differences in heat-pain sensitivity.
Heat induced pain has been shown to follow a positively accelerating power function for groups of subjects, yet the extent to which this applies to individual subjects is unknown. Statistical methods were developed for assessing the goodness of fit and reliability of the power function for data from individual subjects with the aim of using such functions for characterizing individual differences in heat-pain sensitivity. 175 subjects rated ascending and random series of contact heat stimuli with visual analogue scales for pain intensity (VAS-I) and unpleasantness (VAS-A). Curve fitting showed excellent model fit. ⋯ Exponent reliability was high for the ascending series (VAS-I=.92; VAS-A=.91), but considerably lower for the random series (VAS-I=.69; VAS-A=.71). Individual differences constituted 60% of the total variance in pain ratings, whereas stimulus temperature accounted for only 40%. This finding underscores the importance of taking individual differences into account when performing pain studies.
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Controlled Clinical Trial
Increased levels of interstitial potassium but normal levels of muscle IL-6 and LDH in patients with trapezius myalgia.
The mechanisms behind the development of work-related trapezius pain are suggested to involve both peripheral and central components, but the specific contribution of alterations in muscle nociceptive and other substances is not clear. Female patients with chronic trapezius myalgia (N=19; TM) and female controls (N=20; CON) were studied at rest, during 20 min repetitive low-force exercise and recovery, and had their interstitial concentrations of potassium (K(+)), lactate dehydrogenase (LDH), interleukin-6 (IL-6) and collagen turnover determined in the trapezius muscle by the microdialysis technique. K(+) levels were at all time points higher in TM than in CON (P<0.0001). ⋯ Rises in muscle LDH and IL-6 as well as the anabolic ratio for collagen type I was not significantly different between groups. In conclusion, patients with chronic pain in the trapezius muscle had increased levels of interstitial potassium. This finding could be causally related to myalgia or secondary to pain due to deconditioned muscle or altered muscle activity pattern.