Brain : a journal of neurology
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In order to investigate the plasticity of cutaneous sensory abnormalities in neuropathic pain, we monitored sensory and vasomotor effects of diagnostic sympathetic ganglion blocks in 24 patients, who suffered from chronic pain and cutaneous hyperalgesia following peripheral nerve or tissue injury. Ongoing pain was rated on a visual analogue scale, and pain evoked by innocuous tactile and cooling stimuli (hyperalgesia) on a verbal rating scale. Skin temperatures were determined at symmetric sites. ⋯ It could be reversed within minutes by a sympathetic blockade, but returned when sympathetic block subsided. Mechanoreceptor input by itself was not sufficient to maintain or rekindle the central sensitization. This supports the hypothesis that low-grade activity of nociceptors, possibly due to development of alpha-adrenergic sensitivity after injury, is involved in the maintenance of central sensitization.