The sympathetic skin response in the shoulder-hand syndrome complicating tetraplegia.

To determine the utility of the sympathetic skin response (SSR) in studying sympathetic outflow in cervical spinal cord injury (CSCI) patients who develop features of reflex sympathetic dystrophy, we studied seven consecutive CSCI patients with the shoulder-hand syndrome (SHS), and seven patients with similar injuries but without the manifestations of the SHS. The mean SSR amplitude was more than three times greater in patients with the SHS, a statistically significant difference. We restudied six patients with a SHS after symptoms had improved following steroid treatment: the mean amplitude fell significantly, approaching the mean for the control group. When pain was asymmetric, the SSR amplitude was higher in the arm with greater pain. Four of the seven SHS patients demonstrated an unusual pattern of spontaneous cyclical electrical activity during a period of severe pain. We conclude that a SHS complicating CSCI is associated with increased amplitude of the SSR, supporting the theory that sympathetic hyperactivity is important in the pathophysiology of reflex sympathetic dystrophy in this setting.