| 1. |
- Koltzenburg, M, et al.
(author)
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Dynamic and static components of mechanical hyperalgesia in human hairy skin
- 1992
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In: Pain. - : Elsevier BV. - 0304-3959 .- 1872-6623. ; 51:2, s. 207-219
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Journal article (peer-reviewed)abstract
- The principle finding of the present study is that there are two types of mechanical hyperalgesia developing in human hairy skin following injurious stimuli. Mechanical hyperalgesia comprises a dynamic component (brush-evoked pain, allodynia) signalled by large myelinated afferents and a static component (hyperalgesia to pressure stimuli) signalled by unmyelinated afferents. While the static component is only found in the injured area, the dynamic component also extends into a halo of undamaged tissue surrounding the injury. The irritant chemicals, mustard oil or capsaicin, were applied transdermally in 20 subjects to a patch (2 × 2 cm) of hairy skin. Both substances evoked burning pain and hyperalgesia to mechanical stimuli. While stroking normal skin with a cotton bud was perceived only as touch prior to chemical stimulation, there was a distinctly unpleasant sensation afterwards. This component of mechanical hyperalgesia persisted for at least 30 min and was present in the skin exposed to the irritants (primary hyperalgesia) as well as in a zone of untreated skin surrounding the injury (secondary hyperalgesia) measuring 38 ± 4 cm2 after capsaicin. Pressure pain thresholds dropped to 55 ± 8% of baseline level after mustard oil and to 46 ± 9% after capsaicin. However, this drop of thresholds was short-lived, lasting 5 min following mustard oil but persisting more than 30 min following capsaicin treatment. The reduction of pressure pain thresholds was only observed for treated skin areas, but not in the surrounding undamaged tissue from where brush-evoked pain could be evoked. When pressure pain thresholds were lowered, the pain had a burning quality which differed distinctly from the quality of brush-evoked pain. On-going burning pain and both types of mechanical hyperalgesia were critically temperature dependent. Mildly cooling the skin provided instant relief from on-going pain, abolished brush-evoked pain and normalized pressure pain thresholds. Rewarming resulted in a reappearence of on-going pain and hyperalgesia. The effect of a nerve compression block of the superficial radial nerve on these sensations was tested in 14 experiments. When the ability to perceive light touch had been abolished, there was also no touch-evoked pain, indicating that this component of mechanical hyperalgesia is mediated by large-diameter primary afferents. At a later stage of the block when the subjects' ability to perceive cold stimuli had also been lost, application of cool stimuli still eliminated on-going burning pain, suggesting that pain relief afforded by cooling the skin acts at the peripheral receptor level and not by central masking. Importantly, at this stage of the block, when only unmyelinated primary afferents conducted, neither spontaneous pain, nor hyperalgesia to heat, nor the lowered pressure pain threshold had changed significantly. Based on the differences in quality of sensations, in spatial and temporal profiles and in susceptibility to differential nerve blocks, we conclude that irritant chemicals induce a dynamic and static component of mechanical hyperalgesia signalled by large-diameter or unmyelinated fibres, respectively. While the static component may be mediated by sensitized peripheral nociceptors, the dynamic component is probably the consequence of an altered processing of large diameter primary afferent input in the central nervous system subsequent to a maintained barrage of nociceptor activity. The parallel fluctuation of brush-evoked and burning background pain therefore suggest that on-going activity from nociceptors is required to maintain a central state that permits dynamic mechanical hyperalgesia to be expressed in humans.
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| 2. |
- Linton, Steven J., 1952-, et al.
(author)
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A controlled study of the effects of an early intervention on acute musculoskeletal pain problems
- 1993
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In: Pain. - : Elsevier. - 0304-3959 .- 1872-6623. ; 54:3, s. 353-359
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Journal article (peer-reviewed)abstract
- Current conceptions of chronic pain clearly suggest that proper care at the acute stage should prevent the development of chronic problems. Patients (198) seeking help for acute musculoskeletal pain (MSP), e.g., back and neck pain participated in two studies of the effects of an Early Active intervention which underscored 'well' behavior and function compared to a Treatment as Usual control group. The quantity of the Early Active treatment was a median of 1 doctor's appointment and 3 meetings with a physical therapist. Study I concerned patients with a prior history of sick-listing for MSP, while study II involved patients with no prior history of MSP. Treatment satisfaction, pain experience, activities and sickness absenteeism were assessed before, after and at a 12-month follow-up. In study I (patients with a history of MSP), the results showed significant improvements for both groups, but virtually no differences between the groups. Similarly, in study II (no history of MSP) both groups demonstrated significant improvements e.g., for pain intensity and activity levels. However, the Early Active treatment resulted in significantly less sick-listing relative to the control group. Moreover, the risk of developing chronic (> 200 sick days) pain was 8 times lower for the Early Activation group. This investigation shows that relatively simple changes in treatment result in reduced sickness absenteeism for 'first-time' sufferers only. Consequently, the content and timing of treatment for pain appear to be crucial. Properly administered early intervention may therefore decrease sick leave and prevent chronic problems, thus saving considerable resources.
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| 3. |
- Gaston-Johansson, Fannie, 1938, et al.
(author)
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Rheumatoid arthritis: determination of pain characteristics and comparison of RAI and VAS in its measurement.
- 1990
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In: Pain. - 0304-3959. ; 41:1, s. 35-40
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Journal article (peer-reviewed)abstract
- The purposes of this study were to determine pain characteristics in female patients with rheumatoid arthritis (RA) and to determine the relationship between the outcome of the Ritchie Articular Index (RAI) and pain intensity as measured by the visual analogue scale (VAS). The sample consisted of 30 female patients with a definite diagnosis of RA and a functional capacity of class II. The results indicated that the pain fluctuated during the day. The intensity level of present pain was lower than that of usual pain. Eight patients reported that their worse pain occurred several times/day. Ache was the word most frequently chosen by the subjects to denote their pain sensations. A high correlation r = 0.86 (P less than 0.01) was found between the scores of RAI and present pain on the VAS. This finding suggests that the pain in RA is associated with the hyperalgesic state induced by the inflammatory condition associated with RA. There was no significant correlation between blood tests like ERS, WBC and VAS or RAI.
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| 4. |
- Widerström, E G, et al.
(author)
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Relations between experimentally induced tooth pain threshold changes, psychometrics and clinical pain relief following TENS. A retrospective study in patients with long-lasting pain.
- 1992
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In: Pain. - 0304-3959. ; 51:3, s. 281-7
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Journal article (peer-reviewed)abstract
- The present study investigates the relationships between clinical pain relief, physiological and psychological parameters. Out of 50 patients with long-lasting musculoskeletal neck- and shoulder-pain treated with transcutaneous electrical nerve stimulation (TENS), 21 were selected and classified as responders (n = 13) or non-responders (n = 8). Tooth pain thresholds (PT) were measured before and after an experimental TENS treatment and the relative change in PT following the stimulation was calculated. Three psychometric self-inventories were administered: Zung Depression Scale, Spielberger's Trait Anxiety Scale and the Multidimensional Health Locus of Control Scale. Responders (R) and non-responders (NR) differed significantly from each other in the PT measurements as well as on the psychometric scales. NR exhibited higher levels of anxiety and depression, a more pronounced powerful other orientation and no change or a decrease in PT following TENS compared to R. These findings indicate relationships and interactions between physiological and psychological factors in patients with long-lasting pain.
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