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Research paper
Quantifying the pattern of optic tract degeneration in human hemianopia
  1. Rebecca S Millington1,2,
  2. Clarissa L Yasuda3,
  3. Panitha Jindahra4,
  4. Mark Jenkinson1,2,
  5. John L Barbur5,
  6. Christopher Kennard2,
  7. Fernando Cendes3,
  8. Gordon T Plant6,7,
  9. Holly Bridge1,2
  1. 1Oxford Centre for functional Magnetic Resonance Imaging of the Brain (FMRIB), University of Oxford, Oxford, UK
  2. 2Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
  3. 3Department of Neurology, University of Campinas, UNICAMP, Campinas, São Paulo, Brazil
  4. 4Neurology Division, Medicine Department, Ramathibodi Hospital, Bangkok, Thailand
  5. 5Applied Vision Research Centre, City University, London, UK
  6. 6National Hospital for Neurology and Neurosurgery, London, UK
  7. 7Moorfields Eye Hospital, London, UK
  1. Correspondence to Rebecca S Millington, Nuffield Department of Clinical Neurosciences, FMRIB Centre, University of Oxford, John Radcliffe Hospital, Oxford OX3 9DU, UK; rebecca.millington{at}magd.ox.ac.uk

Abstract

Background The existence of transsynaptic retrograde degeneration (TRD) in the human visual system has been established, however the dependence of TRD on different factors such as lesion location, size and manner of lesion acquisition has yet to be quantified.

Methods We obtained T1-weighted structural and diffusion-weighted images for 26 patients with adult-acquired or congenital hemianopia and 12 age-matched controls. The optic tract (OT) was defined and measured in the structural and diffusion-weighted images, and degeneration assessed by comparing the integrity of tracts in the lesioned and in the undamaged hemisphere.

Results OT degeneration was found in all patients with established lesions, regardless of lesion location. In patients with acquired lesions, the larger the initial lesion, the greater is the resulting TRD. However, this was not the case for congenital patients, who generally showed greater degeneration than would be predicted by lesion size. A better predictor of TRD was the size of the visual field deficit, which was correlated with degeneration across all patients. Interestingly, although diffusion-weighted imaging (DWI) is more frequently used to examine white matter tracts, in this study the T1-weighted scans gave a better indication of the extent of tract degeneration.

Conclusions We conclude that TRD of the OT occurs in acquired and congenital hemianopia, is correlated with visual field loss, and is most severe in congenital cases. Understanding the pattern of TRD may help to predict effects of any visual rehabilitation training.

  • VISION
  • MRI
  • STROKE

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