title: Magnetic resonance imaging of disc space infection revisited: temporal changes.
abstract: BACKGROUND
  Magnetic resonance imaging (MRI) has advantages in showing pathologic changes of disc space infection, which is important in clinical treatment. The purpose of this study was to describe the MRI findings of disc space infections in relation to chronicity.
  
  
  METHODS
  MRI of 60 patients from January 1, 2002 to April 30, 2012 in Ottawa Hospital were retrospectively evaluated by two radiologists blindly. All patients had histological confirmation, with 55 having microbiological confirmation as well. These patients were divided into acute (n = 18), subacute (n = 21) and chronic (n = 21) based on histological findings. The following potential signs of MRI finding were assessed: marrow edema, endplate erosions, disk fluid and height change, paraspinal mass, epidural collection, facet fluid and enhancement in the marrow, disc, paraspinal mass, and epidural involvement. Statistical analysis consisted of t- or F-tests and chi-square test.
  
  
  RESULTS
  In the 60 patients, 83 infected discs (single disc in 45 patients, 2-4 discs in 15 patients) were found, including 22 discs in the acute group, 30 discs in the subacute group, and 31 discs in the chronic group. There was a significant difference in the extent of marrow edema between the acute, subacute and chronic groups (P < 0.05), with a gradually increasing extent from acute to chronic. The extent of endplate erosions increased with chronicity, but was not statistically significant. There were significant differences in the disc fluid, epidural collection, and disc enhancement among the acute, subacute and chronic groups, as well as the facet fluid between acute and chronic groups (P < 0.05). There were no significant differences in the present probability of disc height loss, paraspinal mass, and marrow enhancement among the three groups (P > 0.05).
  
  
  CONCLUSIONS
  From acute to chronic infections, the extent of marrow edema and endplate erosions appeared to gradually increase. Epidural collections and facet fluid are most frequently found in the acute group, while disc fluid and disc enhancement are more common in the chronic patients.
authors.affiliation: Department of Medical Imaging, The Ottawa Hospital, University of Ottawa, Canada; Department of Medical Imaging, Zhongshan Hospital of Xiamen University, Xiamen, Fujian 361004, China.
authors.forename: Shaoyin
authors.initials: S
authors.lastname: Duan
authors.affiliation: Department of Medical Imaging, Zhongshan Hospital of Xiamen University, Xiamen, Fujian 361004, China.
authors.forename: Bingqiang
authors.initials: B
authors.lastname: Xu
authors.affiliation: Department of Medical Imaging, The Ottawa Hospital, University of Ottawa, Canada.
authors.forename: Gina Di
authors.initials: GD
authors.lastname: Primio
authors.affiliation: Department of Medical Imaging, The Ottawa Hospital, University of Ottawa, Canada.
authors.forename: Cheemun
authors.initials: C
authors.lastname: Lum
authors.affiliation: Department of Medical Imaging, The Ottawa Hospital, University of Ottawa, Canada; Department of Radiology, Stony Brook Hospital, State University of New York at Stony Brook (Stony Brook University), New York 11794-8460, USA. Email: mschweitzer@toh.on.ca; mark.schweitzer@sbumed.org.
authors.forename: Mark E
authors.initials: ME
authors.lastname: Schweitzer
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015299:Discitis / Q000175:diagnosis*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies