title: Imaging of intraneural edema by using gadolinium-enhanced MR imaging: experimental compression injury.
abstract: OBJECTIVE
  Compressive and entrapment neuropathies are diseases frequently observed on routine clinical examination. A definitive diagnosis based on clinical symptoms and neurologic findings alone is difficult in many cases, however, and electrophysiologic measurement is used as a supplementary diagnostic method. In this study, we examined to use protein tracers (Evans blue albumin or horseradish peroxidase) and gadolinium-enhanced MR imaging to determine the changes of blood-nerve barrier permeability in compressive neuropathies.
  
  
  METHODS
  In dogs, the median nerve was compressed for 1 hour by using five kinds of clips with various strengths (7.5-90-g force). After clip removal, the combined tracers of Evans blue albumin and gadolinium or horseradish peroxidase was administered intravenously as a tracer. After the animals were euthenized, we compared gadolinium-enhanced MR images with Evans blue albumin distribution in the nerve under fluorescence microscopy. The horseradish peroxidase-injected specimens were observed by transmission electron microscopy.
  
  
  RESULTS
  On enhanced MR imaging, intraneural enhancement was caused by 60- and 90-g-force compression after 1 hour. Marked extravasation of protein tracers in the nerve occurred where there was compression by 60- and 90-g-force compression, and capillaries in the nerve showed the opening of tight junction and an increase of vesicular transport under the electron microscopy. This situation indicated breakdown of the blood-nerve barrier, with consequent edema formation and was seen as enhancement on MR imaging.
  
  
  CONCLUSIONS
  Gadolinium-enhanced MR imaging can detect morphologic and functional changes of blood-nerve barrier in the nerve induced by mechanical compression.
authors.affiliation: Physiology Laboratory of Oxford University, Oxford, United Kingdom.
authors.forename: Shigeru
authors.initials: S
authors.lastname: Kobayashi
authors.forename: Adam
authors.initials: A
authors.lastname: Meir
authors.forename: Hisatoshi
authors.initials: H
authors.lastname: Baba
authors.forename: Kenzo
authors.initials: K
authors.lastname: Uchida
authors.forename: Katsuhiko
authors.initials: K
authors.lastname: Hayakawa
mesh_terms: D000818:Animals; D049428:Blood-Nerve Barrier; D003287:Contrast Media; D004285:Dogs; D004487:Edema / Q000175:diagnosis*; D019786:Gadolinium DTPA; D008279:Magnetic Resonance Imaging / Q000379:methods; D008854:Microscopy, Electron; D009408:Nerve Compression Syndromes / Q000175:diagnosis*
chemical_list: D003287:Contrast Media; D019786:Gadolinium DTPA