title: Retinal nerve fiber layer thickness is associated with lesion length in acute optic neuritis.
abstract: BACKGROUND
  Acute optic neuritis occurs with and without papillitis. The presence of papillitis has previously been thought to imply an anterior location of the neuritis, but imaging studies seeking to test this hypothesis have been inconclusive.
  
  
  METHODS
  This prospective observational cohort study included 41 patients with unilateral optic neuritis and 19 healthy volunteers. All patients were evaluated and examined within 28 days of onset of symptoms. The peripapillary retinal nerve fiber layer thickness (RNFLT), an objective quantitative measure of optic nerve head edema, was measured by optical coherence tomography and the length and location of the inflammatory optic nerve lesion were evaluated using MRI.
  
  
  RESULTS
  Ophthalmoscopically, 34% of the patients had papillitis. The retinal nerve fiber layer in affected eyes (mean 123.1 microm) was higher during the acute phase than that of fellow eyes (mean 98.1 microm, p < 0.0001) and higher than that in healthy control eyes (mean 97.1 microm, p < 0.0001). The RNFLT was related to the length of the optic nerve lesion (p = 0.0002), but not to the location of the optic nerve lesions (p = 0.72).
  
  
  CONCLUSIONS
  In this study of the acute phase of optic neuritis, the degree of optic nerve head edema depended upon the extent of the optic nerve lesion, but not on its location. This suggests that factors other than inflammation, such as compromised venous drainage, vascular leakage, impaired axonal transport, and other mechanisms, are involved in the development of optic nerve head edema in optic neuritis.
authors.affiliation: Department of Neurology, Functional Imaging Unit, Glostrup Hospital and University of Copenhagen, 2600 Glostrup, Denmark. klakal01@glo.regionh.dk
authors.forename: K
authors.initials: K
authors.lastname: Kallenbach
authors.forename: H
authors.initials: H
authors.lastname: Simonsen
authors.forename: B
authors.initials: B
authors.lastname: Sander
authors.forename: B
authors.initials: B
authors.lastname: Wanscher
authors.forename: H
authors.initials: H
authors.lastname: Larsson
authors.forename: M
authors.initials: M
authors.lastname: Larsen
authors.forename: J L
authors.initials: JL
authors.lastname: Frederiksen
mesh_terms: D000208:Acute Disease; D000293:Adolescent; D000328:Adult; D015331:Cohort Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009412:Nerve Fibers / Q000473:pathology*; D009900:Optic Nerve / Q000473:pathology*; D009902:Optic Neuritis / Q000150:complications / Q000473:pathology*; D010211:Papilledema / Q000150:complications / Q000473:pathology; D011446:Prospective Studies; D012160:Retina / Q000473:pathology*; D055351:Retinal Neurons / Q000473:pathology; D055815:Young Adult