European journal of pain : EJP
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Neuropathic pain is part of the neurological disease spectrum and may be an expression of severe medical pathology. Painful neuropathies have multiple disguises and may to a certain extent be mimicked by non-neurological pain conditions. Painful neuropathic conditions express themselves with spontaneous and/or abnormal stimulus-evoked pain. ⋯ This is a sound approach and should be pursued. It is mandatory, however, to retain the traditional organ-based diagnostic workup, which should precede further in-depth characterization of specific pain mechanisms. Extensive preparatory work is needed on how to link certain symptoms and signs to specific mechanisms, as elucidated from animal studies, before we can introduce mechanism-coupled treatment strategies.
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The overall aim of this study was to explore the natural course of pain-related fear during the early stage of a new low back pain episode, using a prospective case series design. Specific research questions addressed the existence of typical patterns in individual time series of pain-related fear and sequential relationships between the occurrence of pain-related fear, pain and pain catastrophizing. Forty-four general practice patients who consulted their physician with a new episode of non-specific low back pain were recruited. ⋯ In summary, these results fit in with previous findings in chronic patients. A relevant subgroup of patients who might benefit from early intervention could be identified. These findings support the need for further research into fear mechanisms in acute low back pain.
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Heterotopic noxious conditioning stimulation (HNCS) has been thought to give access to the diffuse noxious inhibitory controls (DNIC) in man, which can be activated in wide-dynamic-range neurons by noxious stimulation from remote areas of the body and form the neurophysiological basis of the phenomenon 'pain inhibits pain'. The latter phenomenon suggests that the subjective experience of pain is a prerequisite for an inhibitory action. The necessity of using painful stimuli as conditioning and as test stimuli to produce inhibitory effects was investigated in the present study, using a HNCS paradigm. ⋯ However, the intensity ratings of the test stimuli indicated inhibitory effects of the conditioning stimuli also upon non-painful levels. Furthermore, non-painful heat as conditioning stimulus also appeared to be capable of decreasing the ratings of the test stimuli at painful levels. The latter two findings suggest: (i) that very strong but subjectively still non-painful stimulation can trigger pain inhibitory effects and (ii) that also subjectively non-painful stimuli are affected by inhibitory influences during HNCS.
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Some patients who have sustained whiplash injuries present with chronic widespread pain and mechanical allodynia. This single-blind, case control matched study of 43 chronic whiplash patients sought to examine psychophysical responses to non-noxious stimuli and their relationship to psychological profiles. Symptom Check List 90-R (SCL-90-R), Neck Disability Index and Shortform McGill Questionnaire were completed prior to testing. ⋯ Pain in response to non-noxious stimulation over presumably healthy tissues suggests that central mechanisms are responsible for ongoing pain in at least some whiplash patients. The additional findings of pain on punctate pressure and hyperalgesic responses to heat and cold stimuli are consistent with enhanced central responsiveness to nociceptor input. These results have important therapeutic and prognostic implications.
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Neuropathic pain represents a series of relatively uncommon chronic pain conditions, caused by lesions or dysfunctions of peripheral or central afferent pathways in the nervous system. The symptoms and signs of neuropathic pain can all be explained by a neuronal hyperexcitability at the site of the nerve lesion, which subsequently and in a dynamic fashion recruits more central sites. The manifestations of such neuronal hyperexcitability are therefore rather similar, irrespective of the causes or sites of the lesions. ⋯ Our understanding of the mechanisms underlying neuronal hyperexcitability has increased dramatically within the last decade, and accordingly, it has been suggested that pain be classified according to a mechanism-based approach. The challenge for an improved understanding of neuropathic pain--which is the key for better treatment--lies in elucidating the relationships between symptoms, signs, aetiology, anatomical lesions, and underlying mechanisms. At present, this is not a trivial task.