title: MR nerve imaging in a prospective cohort of patients with suspected carpal tunnel syndrome.
abstract: OBJECTIVE
  To evaluate the reliability and diagnostic accuracy of high-resolution MRI of the median nerve in a prospectively assembled cohort of subjects with clinically suspected carpal tunnel syndrome (CTS).
  
  
  METHODS
  The authors prospectively identified 120 subjects with clinically suspected CTS from five Seattle-area clinics. All subjects completed a hand-pain diagram and underwent a standardized nerve conduction study (NCS). The reference standard for determining CTS status was a classic or probable hand pain diagram and NCS with a difference >0.3 ms between the 8-cm median and ulnar peak latencies. Readers graded multiple imaging parameters of the MRI on four-point scales. The authors also performed quantitative measurements of both the median nerve and carpal tunnel cross-sectional areas. NCS and MRI were interpreted without knowledge of the other study or the hand pain diagram.
  
  
  RESULTS
  Intrareader reliability was substantial to near perfect (kappa = 0.76 to 0.88). Interreader agreement was lower but still substantial (kappa = 0.60 to 0.67). Sensitivity of MRI was greatest for the overall impression of the images (96%) followed by increased median nerve signal (91%); however, specificities were low (33 to 38%). The length of abnormal signal on T2-weighted images was significantly correlated with nerve conduction latency, and median nerve area was larger at the distal radioulnar joint (15.8 vs 11.8 mm(2)) in patients with CTS. A logistic regression model combining these two MR variables had a receiver operating characteristic area under the curve of 0.85.
  
  
  CONCLUSIONS
  The reliability of MRI is high but the diagnostic accuracy is only moderate compared with a research-definition reference standard.
authors.affiliation: Department of Radiology, School of Medicine, University of Washington, 1959 E Pacific, Seattle, WA 98195, USA. jarvik@u.washington.edu
authors.forename: J G
authors.initials: JG
authors.lastname: Jarvik
authors.forename: E
authors.initials: E
authors.lastname: Yuen
authors.forename: D R
authors.initials: DR
authors.lastname: Haynor
authors.forename: C M
authors.initials: CM
authors.lastname: Bradley
authors.forename: D
authors.initials: D
authors.lastname: Fulton-Kehoe
authors.forename: T
authors.initials: T
authors.lastname: Smith-Weller
authors.forename: R
authors.initials: R
authors.lastname: Wu
authors.forename: M
authors.initials: M
authors.lastname: Kliot
authors.forename: G
authors.initials: G
authors.lastname: Kraft
authors.forename: L
authors.initials: L
authors.lastname: Wang
authors.forename: V
authors.initials: V
authors.lastname: Erlich
authors.forename: P J
authors.initials: PJ
authors.lastname: Heagerty
authors.forename: G M
authors.initials: GM
authors.lastname: Franklin
mesh_terms: D000328:Adult; D002349:Carpal Tunnel Syndrome / Q000473:pathology*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000592:standards*; D008297:Male; D008475:Median Nerve / Q000473:pathology*; D011237:Predictive Value of Tests; D011446:Prospective Studies; D012015:Reference Standards; D015203:Reproducibility of Results