title: Paraspinal Edema Is the Most Sensitive Feature of Lumbar Spinal Epidural Abscess on Unenhanced MRI.
abstract: OBJECTIVE
  Spinal epidural abscess (SEA) is a serious infection requiring prompt treatment and potential neurosurgical intervention. Although contrast-enhanced spine MRI is the mainstay for diagnosis of SEA, unenhanced MRI is typically performed for patients with nonspecific symptoms or insufficient clinical information. We evaluated the sensitivity and specificity of imaging features suggestive of SEA at unenhanced spine MRI.
  
  
  METHODS
  We searched our database for contrast-enhanced lumbar spine MRI examinations from January 1, 2000, through August 1, 2014, with "epidural abscess" in the report. We included 68 patients older than 18 years with an enhancing epidural collection at MRI and surgical (60%), microbiologic (15%), or clinical (25%) confirmation of SEA. Sixty-eight age- and sex-matched control subjects without SEA were also selected. Three readers scored unenhanced MR images on the degree of psoas and paraspinal muscle edema, extent of bone marrow edema, and abnormal disk signal.
  
  
  RESULTS
  Paraspinal edema was highly sensitive (97%) for SEA, with lower sensitivities for psoas (54%), bone marrow (65%), and disk edema (66%). Each of these markers was highly significant in univariate analysis (p < 0.001). A multivariate logistic regression model adjusting for age and sex found that paraspinal (p < 0.001) and bone marrow edema (p = 0.006) were significant independent predictors of SEA (odds ratio, 58; p < 0.001), with a trend toward significance for psoas edema and abnormal disk signal. Psoas muscle edema was the most specific (96%) finding for the presence of SEA.
  
  
  CONCLUSIONS
  Paraspinal edema is highly sensitive for SEA. Familiarity with the findings for SEA at unenhanced MRI could help expedite further definitive evaluation when contrast agent is not administered.
authors.affiliation: 1 Department of Radiology, University of Massachusetts Medical School, Worcester, MA.
authors.forename: Anna
authors.initials: A
authors.lastname: Shifrin
authors.affiliation: 2 Department of Radiology, Zhongda Hospital, Southeast University, Nanjing, Jiangsu, China.
authors.forename: Qin
authors.initials: Q
authors.lastname: Lu
authors.affiliation: 3 Department of Radiology, Massachusetts General Hospital, Boston, MA.
authors.forename: Michael H
authors.initials: MH
authors.lastname: Lev
authors.affiliation: 4 Department of Radiology, Hennepin County Medical Center, Minneapolis, MN.
authors.forename: Timothy M
authors.initials: TM
authors.lastname: Meehan
authors.affiliation: 5 Department of Radiology, Emory University School of Medicine, 1364 Clifton Rd NE, Ste BG20, Atlanta, GA 30322.
authors.forename: Ranliang
authors.initials: R
authors.lastname: Hu
mesh_terms: D003287:Contrast Media; D003937:Diagnosis, Differential; D004487:Edema / Q000000981:diagnostic imaging*; D020802:Epidural Abscess / Q000000981:diagnostic imaging* / Q000628:therapy; D005260:Female; D006801:Humans; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D012680:Sensitivity and Specificity
chemical_list: D003287:Contrast Media
keywords: MRI; abscess; epidural; infection; spine