title: Usefulness of asymmetry score on quantitative three-phase bone scintigraphy in the evaluation of complex regional pain syndrome.
abstract: BACKGROUND
  Complex regional pain syndrome (CRPS) is primarily a clinical diagnosis. Diagnostic imaging in CRPS can be used, especially to exclude other disorders. The sensitivity and specificity of three phase bone scintigraphy (TPBS) for the diagnosis of CRPS is variable throughout the literature.
  
  
  OBJECTIVE
  To establish a simple and effective quantitative approach to help in the diagnosis of CRPS by TPBS.
  
  
  METHODS
  TPBS done in patients (n = 68) with suspected CRPS was analyzed retrospectively. They were classified into bone scan positive group (BSP), bone scan negative group (BSN) and non-CRPS group based on diffusely increased periarticular uptake, symmetrical uptake, and focal uptake respectively. Asymmetry score (AS) was also measured between the affected and unaffected side.
  
  
  RESULTS
  16 patients showed focal uptake, 37 were in BSP group with mean AS score of 1.57 ± 0.5 and 15 were in BSN group with mean AS score of 1.01 ± 0.05. The mean AS was significantly different (P < 0.0001). AS of 1.06 had sensitivity and specificity of 96.43% and 100% respectively (P = 0.0001). There was a trend of negative correlation between the AS and the duration, r = -0.21; however, it was not statistically significant (P = 0.28).
  
  
  CONCLUSIONS
  TPBS should be considered in the evaluation of CRPS to rule out patients who have focal involvement, not diagnostic of CRPS (~24% in this study). Quantitative AS of 1.06 can be included to support visual interpretation in the delayed phase.
authors.affiliation: Department of Nuclear Medicine and Positron Emission Tomography, Postgraduate Institute of Medical Education and Research, Chandigarh, India.
authors.forename: Santhosh
authors.initials: S
authors.lastname: Sampath
authors.forename: Bhagwant Rai
authors.initials: BR
authors.lastname: Mittal
authors.forename: Sasikumar
authors.initials: S
authors.lastname: Arun
authors.forename: Ashwani
authors.initials: A
authors.lastname: Sood
authors.forename: Anish
authors.initials: A
authors.lastname: Bhattacharya
authors.forename: Aman
authors.initials: A
authors.lastname: Sharma
keywords: Asymmetry score; Tc99m methylene diphosphonate; complex regional pain syndrome; three phase bone scan
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