European journal of pain : EJP
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The study assessed the influence of stimulus modality on adaptation or facilitation of pain during tonic cold and tourniquet pressure stimulation. Experimental set-up for the cold stimulation consisted of a thermo-tank with water, cooled to 3 degrees C, circulation pump, electronic thermometer and an electronic 10 cm visual analogue scale (VAS). Experimental set-up for the tonic pressure stimulation consisted of a pneumatic tourniquet cuff, a computer-controlled air compressor, and an electronic VAS. ⋯ The overshoot magnitude was lowest during "VAS 6" session. Adapting and non-adapting/facilitating responses to cold and to pressure during "VAS 6" session were not correlated, suggesting that pain course and therefore stimulus tolerance during tonic stimulation are modality-specific. The results of the study suggest that tolerance of tonic painful pressure and cold stimulations is specific to stimulus modality and may represent separate nociceptive mechanisms.
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To examine the cognitive processing differences in chronic and episodic pain sufferers, auditory event-related potentials (P300 or P3) were recorded in two consecutive trials from 23 chronic lower back pain patients, 22 episodic tension-type headache sufferers, and from 23 age- and sex-matched healthy persons. P3 latency and amplitude showed no difference between groups at first trial. Considering P3 latency habituation, healthy controls and episodic tension-type headache sufferers showed a significant change of P3 latency whereas lower back pain sufferers failed. ⋯ These results may point to a disturbed attentional processing in chronic pain sufferers. Our findings suggest that in spite of a similar cortical information processing, the neurocognitive networks related with decision making and memory processing seem to work differently in chronic pain sufferers from those in episodic pain sufferers in repeating tasks. Taking into consideration the reported P3 habituation abnormalities in chronic migraine patients we can say that not the location of pain but rather its temporal pattern may have a role in disturbed attentional processing.
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The purpose was to investigate the influence of ongoing pain from an inflammatory nociceptive pain with two different disease durations on somatosensory functions and the effect of heterotopic noxious conditioning stimulation (HNCS) on 'diffuse noxious inhibitory controls' (DNIC) related mechanisms. Eleven patients with rheumatoid arthritis of a short duration (<1 year) (RA1), and 10 patients with rheumatoid arthritis of longer duration (>5 years) (RA5) as well as 21 age- and sex-matched healthy controls participated. Pressure pain sensitivity, low threshold mechanoreceptive function and thermal sensitivity, including thermal pain, were assessed over a painful and inflamed joint as well as in a pain-free area, i.e. the right thigh before HNCS (cold-pressor test) and repeated at the thigh only during and following HNCS. ⋯ In conclusion, over an inflamed joint allodynia to pressure was found in both RA groups, with additional sensory abnormalities in RA5. In a non-painful area, allodynia to pressure was found in RA5, suggesting altered central processing of somatosensory functions in RA5 patients. The response to HNCS was similar in both RA groups and controls, indicating preserved function of DNIC-related mechanisms.
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Reflex sympathetic dystrophy (RSD), also known as complex regional pain syndrome type I (CRPS I), is a disabling neuropathic pain syndrome. Controversy exists about the effectiveness of therapeutic interventions for the management of RSD/CRPS I. In order to ascertain appropriate therapies we conducted a review of existing randomized controlled trials of therapies for this disabling disease. ⋯ The search for trials concerning prevention of RSD/CRPS I resulted in two eligible studies. Both were of high quality and dealt with different interventions. There is limited evidence for their preventive effect.