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Cutaneous pain threshold changes after sympathetic block in reflex dystrophies
Paolo Procacci1, Fabio Francini, Massimo Zoppi
1Pain Center, Clinica Medica Generale, University of Florence, Florence Italy Istituto di Fisiologia Umana, University of Florence, Florence Italy.
Abstract:
In a group of 30 subjects suffering from sympathetic reflex dystrophies of the limbs, the sympathetic ganglia of the affected side were blocked with a local anesthetic. Using an original method, we measured the cutaneous pain threshold before the block and at prefixed intervals after the block during a period of 2 days. In all subjects the cutaneous pain threshold showed damped oscillations both in the limb ipsilateral to the block and in the contralateral one. The analysis of these oscillations showed: (a) that the sympathetic control of the cutaneous pain threshold may be exerted through a negative feedback loop (skin-afferent input-CNS-sympathetic output-skin); (b) that the afferent discharge of a limb controls the contralateral sympathetic output through central mechanisms.