title: Interaction of hyperalgesia and sensory loss in complex regional pain syndrome type I (CRPS I).
abstract: BACKGROUND
  Sensory abnormalities are a key feature of Complex Regional Pain Syndrome (CRPS). In order to characterise these changes in patients suffering from acute or chronic CRPS I, we used Quantitative Sensory Testing (QST) in comparison to an age and gender matched control group.
  
  
  METHODS
  61 patients presenting with CRPS I of the upper extremity and 56 healthy subjects were prospectively assessed using QST. The patients' warm and cold detection thresholds (WDT; CDT), the heat and cold pain thresholds (HPT; CPT) and the occurrence of paradoxical heat sensation (PHS) were observed.
  
  
  RESULTS
  In acute CRPS I, patients showed warm and cold hyperalgesia, indicated by significant changes in HPT and CPT. WDT and CDT were significantly increased as well, indicating warm and cold hypoaesthesia. In chronic CRPS, thermal hyperalgesia declined, but CDT as well as WDT further deteriorated. Solely patients with acute CRPS displayed PHS. To a minor degree, all QST changes were also present on the contralateral limb.
  
  
  CONCLUSIONS
  We propose three pathomechanisms of CRPS I, which follow a distinct time course: Thermal hyperalgesia, observed in acute CRPS, indicates an ongoing aseptic peripheral inflammation. Thermal hypoaesthesia, as detected in acute and chronic CRPS, signals a degeneration of A-delta and C-fibres, which further deteriorates in chronic CRPS. PHS in acute CRPS I indicates that both inflammation and degeneration are present, whilst in chronic CRPS I, the pathomechanism of degeneration dominates, signalled by the absence of PHS. The contralateral changes observed strongly suggest the involvement of the central nervous system.
authors.affiliation: Department of Anaesthesiology, Ludwig-Maximilians-Universität München, Munich, Germany. vhuge@med.uni-muenchen.de
authors.forename: Volker
authors.initials: V
authors.lastname: Huge
authors.forename: Meike
authors.initials: M
authors.lastname: Lauchart
authors.forename: Stefanie
authors.initials: S
authors.lastname: Förderreuther
authors.forename: Wibke
authors.initials: W
authors.lastname: Kaufhold
authors.forename: Michael
authors.initials: M
authors.lastname: Valet
authors.forename: Shahnaz Christina
authors.initials: SC
authors.lastname: Azad
authors.forename: Antje
authors.initials: A
authors.lastname: Beyer
authors.forename: Walter
authors.initials: W
authors.lastname: Magerl
mesh_terms: D000328:Adult; D000368:Aged; D000465:Algorithms; D016022:Case-Control Studies; D003080:Cold Temperature; D005260:Female; D006358:Hot Temperature; D006801:Humans; D006930:Hyperalgesia / Q000150:complications / Q000175:diagnosis*; D007249:Inflammation; D008297:Male; D008875:Middle Aged; D010147:Pain Measurement; D011446:Prospective Studies; D012019:Reflex Sympathetic Dystrophy / Q000150:complications / Q000175:diagnosis*