Brain : a journal of neurology
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Brush-evoked pain (mechanical allodynia, dynamic mechanical hyperalgesia) is a hallmark of neuropathic and inflammatory pain states. Here we have examined the neural mechanisms that induce and maintain this component of mechanical hyperalgesia. The principle finding of these experiments is that the severity of brush-evoked pain correlates with the intensity of background pain in patients suffering from chronic painful neuropathies and in normal subjects with acute experimental chemogenic pain. ⋯ In those individuals, an increase of skin temperature produced a graded increase of their ongoing pain which was closely correlated (r = 0.94) with the level of brush-evoked pain. In the remaining five patients there was no heat hyperalgesia and consequently no aggravation of pain by increases of skin temperature. Nevertheless when the intensity of the background pain fluctuated spontaneously there were also parallel changes (r = 0.88) of the severity of brush-evoked pain.(ABSTRACT TRUNCATED AT 400 WORDS)