Diagnosing sensory abnormalities with either normal values or values from contralateral skin - Comparison of two approaches in complex regional pain syndrome I

Background: To diagnose sensory abnormalities, patient values can be compar ed with values of the general population (absolute approach) or to values m easured at contralateral homologous skin (relative approach). The current s tudy gives normal values for both approaches and compares the advantages of each method by applying the technique to patients with complex regional pa in syndrome type I (CRPS I). Methods: In 50 healthy control subjects, sensory and pain thresholds were m easured for pressure, warmth, and cold on both wrists and both feet. In 53 patients with unilateral CRPS I (33 hand, 20 foot), the same assessments we re conducted twice, at an interval of 1 month. Results: In control subjects, contralateral homologous sides have approxima tely the same sensitivity, supporting the validity of the relative approach in patients. Hypoesthesia and allodynia fan be diagnosed by either the abs olute or relative approach, whereas hyperesthesia and hypoalgesia can only be Identified with the relative approach. The two approaches obtain differe nt results in 20% of cases. Age, gender, and subject criteria may influence the absolute but not the relative approach Both approaches are comparable with regard to reproducibility. Frequency distributions of sensory abnormal ities in chronic CRPS I are presented. The most frequent diagnoses were col d allodynia and mechanical hypoesthesia and allodynia. Conclusions: To divide sensory characteristics into a binary classification of "normal" and "abnormal," the relative approach is the best choice, with the exception of cases in which the contralateral homologous side is absen t or affected by disease. The authors recommend the relative approach for b oth research and clinical purposes.