Comparison of current perception threshold between each side in unilateral complex regional pain syndrome patients does not measure the patient's pain.

The current perception threshold (CPT) test has been developed as one of the neuroselective sensory nerve conduction threshold tests. The score of the CPT of the affected side subtracted from the score of the CPT of the unaffected side in complex regional pain syndrome (CRPS) is expected to show pain objectively. The purpose of this study is to examine first whether the CPT of the affected side is generally lower than that of the unaffected side, and second, whether the greater score shows the more intense pain. The CPT of each side in 25 patients with unilateral CRPS type I was measured and compared. For the 2000 Hz stimulus, the CPT of the affected side was 2677 +/- 262 microAmp (mean +/- standard error) and the CPT of the unaffected side was 2194 +/- 247 microAmp (p = 0.0149). For the 250 Hz stimulus, the CPT was 876 +/- 117 microAmp and 721 +/- 73 microAmp respectively (p > 0.05). For the 5 Hz stimulus, the CPT was 730 +/- 105 microAmp and 448 +/- 56 microAmp respectively (p = 0.0018). In 2000 Hz, 250 Hz, and 5 Hz stimuli, the CPT of the affected side was higher than that of the unaffected side. This shows that generally the affected side is less sensitive than the unaffected side in terms of current perception. The score of the CPT of the affected side subtracted from the score of the CPT of the unaffected side in CRPS does not measure the patient's pain.