title: Wallerian and trans-synaptic degeneration contribute to optic radiation damage in multiple sclerosis: a diffusion tensor MRI study.
abstract: BACKGROUND
  Optic radiation (OR) damage occurs in multiple sclerosis (MS).
  
  
  OBJECTIVE
  The purpose of this study was to explore the contribution of local and distant mechanisms associated with OR damage in MS.
  
  
  METHODS
  Diffusion tensor (DT) magnetic resonance imaging (MRI) tractography probability maps of the ORs were derived from 102 MS patients and 11 controls. Between-group differences of OR normal-appearing white matter (NAWM) damage and topographical distribution of OR damage were assessed using quantitative and voxel-wise analyses, considering the influence of previous optic neuritis (ON+) and T2 OR lesions (T2 OR+).
  
  
  RESULTS
  OR NAWM diffusivity abnormalities were more severe in ON+ patients vs patients without previous optic neuritis (ON-) and T2 OR+ vs T2 OR- patients. Damage to the anterior portions of the ORs was more severe in ON+ vs ON- patients. Compared to controls and T2 OR- patients, T2 OR+ patients experienced a more distributed pattern of DT MRI abnormalities along the ORs, with an increased axial diffusivity limited to the anterior portions of the ORs. In T2 OR+ group, ON+ vs ON- patients showed DT MRI abnormalities in the middle portion of the ORs, in correspondence with focal lesions. OR damage correlated with OR T2 lesion volume, visual dysfunction and optic nerve atrophy.
  
  
  CONCLUSIONS
  Both trans-synaptic degeneration secondary to optic nerve damage and Wallerian degeneration due to local T2 lesions contribute to OR damage in MS.
authors.affiliation: Neuroimaging Research Unit, Vita-Salute San Raffaele University, Italy.
authors.forename: Maria A
authors.initials: MA
authors.lastname: Rocca
authors.forename: Sarlota
authors.initials: S
authors.lastname: Mesaros
authors.forename: Paolo
authors.initials: P
authors.lastname: Preziosa
authors.forename: Elisabetta
authors.initials: E
authors.lastname: Pagani
authors.forename: Tatjana
authors.initials: T
authors.lastname: Stosic-Opincal
authors.forename: Irena
authors.initials: I
authors.lastname: Dujmovic-Basuroski
authors.forename: Jelena
authors.initials: J
authors.lastname: Drulovic
authors.forename: Massimo
authors.initials: M
authors.lastname: Filippi
mesh_terms: D000328:Adult; D001284:Atrophy; D001931:Brain Mapping; D056324:Diffusion Tensor Imaging; D004185:Disability Evaluation; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008297:Male; D008875:Middle Aged; D009103:Multiple Sclerosis / Q000150:complications* / Q000473:pathology*; D009900:Optic Nerve / Q000473:pathology; D009902:Optic Neuritis / Q000209:etiology / Q000473:pathology; D012183:Retrograde Degeneration / Q000209:etiology* / Q000473:pathology*; D014795:Visual Pathways / Q000473:pathology*; D014855:Wallerian Degeneration / Q000209:etiology* / Q000473:pathology*; D055815:Young Adult
keywords: Multiple sclerosis; diffusion tensor MRI; optic radiations; visual impairment; voxel-based analysis