The combination of direct scaling techniques and sensory tests serves to characterize the severity of persistent and intermittent pain conditions such as CRPS, fibromyalgia, and IBS as well as at least part of the pathophysiological basis for these conditions. Thus, such tests help characterize these pain conditions and thereby aid in diagnoses. Perhaps even more important is the potential capacity for such tests to provide a strategy of matching treatments to mechanisms. For example, temporal summation of A-beta allodynia may be mediated by NMDA receptor mechanisms. If this is the case and if this type of allodynia is present in some but not all CRPS patients (37% in the study described above), then a clinical trial of a NMDA receptor blocker might detect a clinical benefit only if patients had been carefully examined for the presence of this particular sensory abnormality. In another example, evoked pains that radiate (i.e., shooting pain) may be particularly responsive to treatment with anticonvulsants. Sensory tests may also be used in combination with local anesthetic blocks to identify peripheral sources of tonic impulse input that sustain neuropathic and other types of pain conditions. An obvious example is that of using lidocaine patches to treat postherpetic neuralgia. This same principle may be used to treat IBS (52).
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