Complex regional pain syndrome (CRPS) is characterised by autonomic, sensory, and motor disturbances. The underlying mechanisms of the autonomic changes in CPRS are unknown. However, it has been postulated that sympathetic inhibition in the acute phase with locally reduced levels of
noradrenaline is followed by an up-regulation of alpha-
adrenoceptors in chronic CRPS leading to
denervation supersensitivity to
catecholamines. This exploratory study examined the effect of cutaneous sympathetic activation and inhibition on cutaneous
noradrenaline release, vascular reactivity, and
pain in CRPS patients and in healthy volunteers. Seven patients and nine controls completed whole-body cooling (sympathetic activation) and heating (sympathetic inhibition) induced by a whole-body thermal suit with simultaneous measurement of the skin temperature, skin blood flow, and release of dermal
noradrenaline. CRPS
pain and the perceived skin temperature were measured every 5 min during thermal exposure, while
noradrenaline was determined from cutaneous microdialysate collected every 20 min throughout the study period. Cooling induced peripheral sympathetic activation in patients and controls with significant increases in dermal
noradrenaline, vasoconstriction, and reduction in skin temperature. The main findings were that the
noradrenaline response did not differ between patients and controls or between the CRPS hand and the contralateral unaffected hand, suggesting that the evoked
noradrenaline release from the cutaneous sympathetic postganglionic fibres is preserved in chronic CRPS patients.