Pain
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Psychological and social factors have been shown, separately, to predict outcome in individuals with chronic low back pain. Few previous studies, however, have integrated both psychological and social factors, using prospective study of clinic populations of low back pain patients, to identify which are the most important targets for treatment. One hundred and eight patients with chronic low back pain, newly referred to an orthopaedic outpatient clinic, completed assessments of demographic characteristics, details of back pain, measures of anxiety and depression (Hospital Anxiety and Depression Scale, HADS), fearful beliefs about pain (Fear Avoidance Beliefs Questionnaire), social stresses (Life Events and Difficulties Schedule) and physical aspects of health-related quality of life [SF-36 Physical Component summary Score scale (PCS)]. ⋯ Number of healthcare contacts over the 6 months ranged from 1 to 29, and was independently predicted by perceived cause of pain [Incident Rate Ratio (IRR)=1.46, p=0.03], Fear Avoidance Beliefs about work (IRR=1.02, p=0.009) and back pain related social difficulties (IRR=1.16, p=0.03). To conclude, anxiety, depression, fear avoidance beliefs relating to work and back pain related stresses predict impairment in subsequent physical health-related quality of life and number of healthcare contacts. Interventions targeting these psychosocial variables in clinic patients may lead to improved quality of life and healthcare costs.
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Increased blood pressure and sweet taste are often associated with decreased pain sensitivity. Animal research suggests that endogenous opioids are involved in both these relationships. Fifty-eight healthy young adults (36 male, 22 female) participated in two sessions receiving a placebo tablet or 50mg of naltrexone on counterbalanced days. ⋯ However, the GLM of tolerance also produced a significant drug by DBP interaction suggesting that blood pressure-related analgesia is at least partially opioid-mediated. Also participants with higher DBP showed dampened mood reactivity to the experiment, which was partially reversible by naltrexone. These results are consistent with findings suggesting that endogenous opioid activity may contribute to generally reduced pain sensitivity, and perhaps mood reactivity, in those with higher BP.
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To assess whether pseudoradicular low-back pain may be associated with subclinical sensory deficits in the distal extremity, we applied the quantitative sensory testing protocol of the German Research Network on Neuropathic Pain (DFNS) in 15 patients with pseudoradicular pain distribution. Sixteen age- and gender-matched healthy control subjects as well as 12 patients with radicular pain syndromes (L4-S1) were studied with the same protocol. Radicular pain was diagnosed using clinical criteria (pain radiation beyond the knee, motor-, sensory-, or reflex deficits, positive Laségue's test). ⋯ In contrast to some central pain syndromes this sensory loss involved predominantly large fiber functions. The subclinical sensory loss in pseudoradicular cases suggests that these patients may also have a neuropathic component of their chronic pain. The spatial incongruence of pain and sensory loss in pseudoradicular pain, however, may also indicate that the two are not causally related.
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A novel prognostic approach to defining chronic pain was developed in a US primary care low back pain population, using a combination of information about pain history, current status and likely prognosis. We tested whether this method was generalizable to a UK population. A prospective cohort of 426 patients who consulted with back pain at one of five UK general practices, and who returned follow-up information 1-year later were included. ⋯ The cut-points for probable and possible chronic pain developed in the US population (80% and 50% probability of future clinically significant back pain, respectively) were appropriate for the UK population, but the cut-point for classifying people at low risk (20% probability) was not replicated in the UK sample. The newly derived cut-points in the UK sample were similar; they remained the same for probable chronic pain, were slightly increased for possible chronic pain, and slightly reduced for those at intermediate or low risk. This method for defining chronic pain prospectively, using risk thresholds for future clinically significant pain, appears to be generalizable to a UK back pain population, particularly for identifying probable chronic pain, and may be generalizable to other primary care low back pain populations.
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This fMRI study investigates the influence of a rating procedure on BOLD signals in common pain-activated cortical brain regions. Painful and non-painful mechanical impact stimuli were applied to the left hand of healthy volunteers. Subjects performed ratings of the perceived intensity during every second stimulation period by operating a visual analogue scale with the right hand. ⋯ Only the responses in the S1 projection field of the stimulated hand following pain were not influenced by the rating procedure. Furthermore, activations in the right and left posterior insular cortex and in the left superior frontal gyrus showed an opposite pattern, namely a stronger BOLD signal during "non-rating". We concluded: (1) Cortical areas regularly activated by painful stimuli may also be activated by touch stimulation. (2) Enhancement of the BOLD contrast by a rating procedure is probably an effect of closer stimulus evaluation and attention focussing. (3) In contrast to most other cortical regions, the posterior insular cortex, which is crucial for the integration of interoceptive afferent input, shows stronger responses in the absence of ratings, which points to a unique role of this region in the processing of somato-visceral information.