Diagnosis of Post-Traumatic Complex Regional Pain Syndrome of the Hand: Current Role of Sympathetic Skin Response and Three-Phase Bone Scintigraphy

Abstract

To evaluate the role of sympathetic skin response (SSR) and three-phase bone scintigraphy (TPBS) in the diagnosis of complex regional pain syndrome (CRPS). 60 patients with CRPS of the hand were recruited. TPBS was performed using a bolus injection of 20 mCi of Tc-99m methylene diphosphonate in an antecubital vein and blood flow (first phase) image, blood pool (second phase) image, and delayed (third phase) image obtained. Patients were considered to have CRPS when the blood pool and blood flow images showed diffuse asymmetric uptake, or when the delayed image indicated increased asymmetric periarticular uptake. SSR was measured simultaneously in the affected and unaffected hands. Standard surface electromyogram disc electrodes were applied to the palm and dorsum of both hands. Electrical stimuli were applied to the skin at the base of little and ring fingers of the unaffected hand. Patients were considered abnormal when response was absent or the peak-to-peak amplitude was <50% of the contralateral hand in at least 2 readings. The delayed phase of TPBS tested positive in all; the first and second phases tested positive in 54 (90%) and 56 (93%) of the patients, respectively. Four of the 6 patients with a negative first phase had had symptoms persisting for more than 6 months, and the other 2 for about 3 to 6 months. No patient presenting within 3 months had a negative scan. SSR was absent in 16 (27%) patients and normal in 44 (73%). 11 (79%) of 14 patients who presented more than 6 months after symptom onset displayed an abnormal SSR, while only 10% of those presenting within 3 to 6 months and 11% of those presenting within 3 months had an abnormal SSR. 12 (75%) of the 16 patients with abnormal SSR had associated decreased sweating, compared with 2 (4.5%) of the 44 patients with a normal SSR. TPBS is a very sensitive corroborative test to confirm the clinical suspicion of CRPS during the initial stages, but not in late cases. SSR can be used to document the sympathetic dysfunction in cases having an associated sweating abnormality and may have some diagnostic value in late cases of CRPS, when TPBS is less reliable.