Loss of Surround Inhibition and After Sensation as Diagnostic Parameters of Complex Regional Pain Syndrome

Complex Regional Pain Syndrome (CRPS) is a severe chronic pain condition. Patients with CRPS experience allodynia, hyperalgesia, autonomic dysfunction, movement difficulties and dystrophic changes. However other characteristics that may be unique to the pain in CRPS require further study. This study evaluated pain parameters in ninety five subjects composed of three groups: healthy pain free controls, patients with radiculopathy and CRPS patients. Healthy subjects were tested in all four extremities, whereas radiculopathy and CRPS patients were tested only on the most affected extremity. All subjects were tested for the following pain parameters: thermal allodynia, mechanical static and dynamic allodynia, windup, and a hyperalgesic mechanical stimulus. All subjects were also evaluated for autonomic dysfunction, movement disorder and dystrophic skin changes. Statistically significant differences were found between both pain groups and the healthy control subjects as well as between the two pain groups. The finding that statistically differentiated CRPS from radiculopathy and normal controls was pain spread following an algesic mechanical and cold stimulus as well as after sensations to these stimuli. The study demonstrated a simple bedside test that discriminated between CRPS, radiculopathy and healthy control subjects.