Pain
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Comparative Study
The role of heterosynaptic facilitation in long-term potentiation (LTP) of human pain sensation.
Long-term potentiation (LTP) of nociceptive synaptic transmission induced by high-frequency electrical stimulation (HFS) predominantly modulates natural somatosensory perceptions mediated by Adelta- and Abeta-fibers in humans at the site of conditioning stimulation. The relative contribution of homo- and heterosynaptic mechanisms underlying those perceptual changes remained unclear. We therefore compared changes of the somatosensory profile between a conditioned skin site (homotopic zone) and an area adjacent to conditioning HFS (heterotopic zone). ⋯ Moreover, a small decrease of thresholds to blunt pressure was found at both zones (p<0.05). Pain summation (windup ratio), mechanical detection threshold as well as vibration detection threshold remained unchanged. Because none of the changes in sensory parameters was unique for the site of conditioning stimulation, these data suggest that heterosynaptic interactions are the predominant mechanism of LTP in nociceptive pathways.
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Multicenter Study
Post-trauma ratings of pre-collision pain and psychological distress predict poor outcome following acute whiplash trauma: a 12-month follow-up study.
Patients with acute whiplash trauma were followed to examine if post-trauma ratings of pre-collision pain and psychological distress were associated with reduced work capability and neck pain at 12 months follow-up. The study included 740 consecutive patients (474 females, 266 males) referred from emergency departments or primary care after car accidents in four counties in Denmark. After the collision patients received a questionnaire on psychological distress, unspecified pain and socio-demographics and 12 months later a follow-up on work capability and neck pain was performed. ⋯ In conclusion unspecified as opposed to specified pain (neck pain) before the collision is associated with poor recovery and high accumulation of pre-collision psychological distress is associated with considerable neck pain at follow-up. However, no conclusions on causality can be drawn. Personal characteristics before the collision are important for recovery and attention to pre-collision characteristics may contribute to the prevention of poor recovery after acute whiplash trauma.
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A prognostic approach to defining chronic pain has been proposed as an alternative to traditional definitions based on retrospective duration of pain. While this new approach performs well in low back pain (LBP), headache and orofacial pain, it is not known whether it translates to regional pain syndromes with an underlying pathological component, such as osteoarthritis (OA). We investigated the performance of this approach in a population-based cohort of older adults reporting knee pain, with a spectrum of radiographic knee OA. 676 adults (50 years+) attended a research clinic and were followed up at 18 months and 3 years. ⋯ The derived cut-points suggested a lower threshold for each of the risk groups than the previous LBP work. This prognostic approach to defining chronic pain appears to translate well to knee pain. Different cut-points for defining risk groups may be needed for different pain syndromes.
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Previous research supports the fear-avoidance model in explaining the transition from acute to chronic non-specific musculoskeletal pain. However, there is still little knowledge on when this vicious circle of pain, disability, pain catastrophizing and fear of movement starts. We performed a daily diary study in 42 patients with acute whiplash injury. ⋯ We also examined the reverse association, that is, whether the changes in pain predict changes in the next day's fear of movement and pain catastrophizing. Although for the fear of movement the model reached significance, the amount of explained variance was negligible. In conclusion, this study provides evidence that already in the early stages of whiplash-related complaints, significant associations between fear of movement and pain intensity and disability occur, and that this association may be predictive of the persistence of pain.