Sympathetic Dysfunction in Long-term Complex Regional Pain Syndrome

Abstract

Malfunction of the sympathetic nervous system (SNS) is common in early complex regional pain syndrome type I (CRPS I). This study was designed to evaluate the function of the SNS in patients with chronic CRPS I and to correlate the obtained data with hand function measurements. Thirty-two patients of both the sexes in whom the diagnosis of CRPS I of the upper extremity had been established for at least 3 years before they were included in the study. Besides a hand outcomes questionnaire [Michigan Hand Outcome Questionnaire, (MHQ)] the patients underwent a standardized testing of the peripheral sympathetic nervous system (pSNS) using laser Doppler flowmetry (LDF). Mean time since initial diagnosis was 4.6+/-2.1 years. The mean MHQ score of the affected limb was 57.3+/-17 compared with 69.4+/-13.7 for the unaffected hand (P=0.002). Twenty patients (62.5%) still demonstrated pathologic results regarding the pSNS function (mean sympathetic reflex 0.18+/-0.11, normal range>0.38). We found no statistically significant correlation between pSNS function either with the clinical outcome as measured by MHQ (r=0.246; P=0.175), or with the level of pain (r=0.132; P=0.473). Even 5 years after the diagnosis of CRPS I of the upper extremity we detected significant impairments of the pSNS in nearly two thirds of our patients. Patients still have pain and present with a significant deterioration of their hand function in comparison with the not affected hand. In our study we could not identify any correlation between pSNS function and clinical outcome as measured by MHQ.