title: Focal demyelinative damage and neighboring white matter integrity: an optic neuritis study.
abstract: BACKGROUND
  Neuronal loss following damage is often greater than expected from the severity of injury to the nerve itself. The visual pathways, which comprise a well-defined system, and optic neuritis (ON), which is usually a discrete event, make a fine model to study this phenomenon.
  
  
  OBJECTIVE
  Understand the effect of focal optic nerve demyelination on neighboring white matter.
  
  
  METHODS
  Diffusion tensor imaging and probabilistic tractography were used to identify and characterize the optic tracts and radiations of 17 ON and matched controls. Data were correlated with retinal nerve fiber layer (RNFL) thickness.
  
  
  RESULTS
  Patients' optic tracts exhibited reduced axial diffusivity, which correlated with RNFL thickness values. Patients' optic radiations demonstrated intact axial diffusivity but reduced fractional anisotropy and elevated radial diffusivity, which could be explained by intra-bundle lesions. No correlations were found between diffusivity measurements in patients' optic tracts and radiations; or between RNFL thickness and optic radiations' diffusivity.
  
  
  CONCLUSIONS
  Following ON, chronic axonal loss develops distally in the optic tracts, demonstrating Wallerian degeneration. Degeneration did not proceed to the optic radiations, opposing anterograde trans-neuronal changes. DTI in ON provides fine in-vivo human model for studying histological abnormalities in normal appearing white matter, localized in close proximity to damaged bundle.
authors.affiliation: Department of Neurology, The Agnes Ginges Center for Human Neurogenetics, Hadassah Hebrew-University Medical Center, Jerusalem, Israel.
authors.forename: N
authors.initials: N
authors.lastname: Raz
authors.affiliation: Department of Neurology, The Agnes Ginges Center for Human Neurogenetics, Hadassah Hebrew-University Medical Center, Jerusalem, Israel.
authors.forename: A S
authors.initials: AS
authors.lastname: Bick
authors.affiliation: Department of Neurology, The Agnes Ginges Center for Human Neurogenetics, Hadassah Hebrew-University Medical Center, Jerusalem, Israel.
authors.forename: T
authors.initials: T
authors.lastname: Ben-Hur
authors.affiliation: Department of Neurology, The Agnes Ginges Center for Human Neurogenetics, Hadassah Hebrew-University Medical Center, Jerusalem, Israel netta@hadassah.org.il.
authors.forename: N
authors.initials: N
authors.lastname: Levin
mesh_terms: D000328:Adult; D001369:Axons / Q000473:pathology; D003430:Cross-Sectional Studies; D003711:Demyelinating Diseases / Q000473:pathology*; D056324:Diffusion Tensor Imaging; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009900:Optic Nerve / Q000473:pathology; D009902:Optic Neuritis / Q000473:pathology*; D013569:Synapses / Q000473:pathology; D014855:Wallerian Degeneration / Q000473:pathology; D066127:White Matter / Q000473:pathology*; D055815:Young Adult
keywords: DTI; Optic neuritis; axonal loss; demyelination; optic radiation; optic tract