Sympathetic skin response in patients with reflex sympathetic dystrophy

The sympathetic skin response (SSR) originates from synchronized activation of the sweat glands as a response to a volley discharge in efferent sympathetic nerve fibres. The aim of the study was to verify the diagnostic value of SSR in patients with reflex sympathetic dystrophy (RSD). SSR was recorded in 20 normal subjects and in 24 patients with predominantly chronic RSD. In normal subjects inter- and intra-individually different mono-, bi- and triphasic potentials could be recorded without difference of the waveform from side to side. SSR abnormalities were found in 15 patients and correlated with the severity of the disease. In patients with slight dystrophies, SSR was predominantly normal. In intermediate dystrophies, mainly differences of the SSR waveform between sides could be recorded, indicating unilateral sudomotor dysfunction. In severe dystrophies abnormalities of SSR amplitude or latency were found, indicating more serious disturbance of sudomotor activity, possibly due to a lesion of sympathetic fibres. The SSR provides useful information on sudomotor dysfunction in patients with RSD. However, as there is no consensus in the literature for the clinical criteria to diagnose RSD, it is not yet possible to determine the final diagnostic value of SSR for the diagnoses of RSD.