Pathological gustatory sweating and flushing can develop after injury to preganglionic cervico-thoracic sympathetic fibres, an unavoidable consequence of resecting that part of the sympathetic chain. The mechanism of this abnormal response is uncertain; conceivably, though, regeneration of injured salivatory fibres or collateral sprouting from nearby intact fibres creates aberrant connections between salivatory fibres and denervated vasomotor and sudomotor neurons in the superior cervical ganglion.(7) Commands to salivate would then be translated into commands to sweat and flush in the distribution of sympathetic denervation. Cross-innervation lower down in the stellate ganglion can also produce unusual and potentially distressing autonomic disturbances in the sympathetically-denervated arm (e.g., piloerection while eating).(8)
Drummond PD. A caution about surgical treatment for facial blushing. British Journal of Dermatology 2000; volume 142: pages 194-195.
"Sympathectomy is a technique about which we have limited knowledge, applied to disorders about which we have little understanding." Associate Professor Robert Boas, Faculty of Pain Medicine of the Australasian College of Anaesthetists and the Royal College of Anaesthetists, The Journal of Pain, Vol 1, No 4 (Winter), 2000: pp 258-260