Lateralized occipital degeneration in posterior cortical atrophy predicts visual field deficits.
Posterior cortical atrophy (PCA), the visual variant of Alzheimer's disease, leads to high-level visual deficits such as alexia or agnosia. Visual field deficits have also been identified, but often inconsistently reported. Little is known about the pattern of visual field deficits or the underlying cortical changes leading to this visual loss.



Multi-modal magnetic resonance imaging was used to investigate differences in gray matter volume, cortical thickness, white matter microstructure and functional activity in patients with PCA compared to age-matched controls. Additional analyses investigated hemispheric asymmetries in these metrics according to the visual field most affected by the disease.



Analysis of structural data indicated considerable loss of gray matter in the occipital and parietal cortices, lateralized to the hemisphere contralateral to the visual loss. This lateralized pattern of gray matter loss was also evident in the hippocampus and parahippocampal gyrus. Diffusion-weighted imaging showed considerable effects of PCA on white matter microstructure in the occipital cortex, and in the corpus callosum. The change in white matter was only lateralized in the occipital lobe, however, with greatest change in the optic radiation contralateral to the visual field deficit. Indeed, there was a significant correlation between the laterality of the optic radiation microstructure and visual field loss.



Detailed brain imaging shows that the asymmetric visual field deficits in patients with PCA reflect the pattern of degeneration of both white and gray matter in the occipital lobe. Understanding the nature of both visual field deficits and the neurodegenerative brain changes in PCA may improve diagnosis and understanding of this disease.
Oxford Centre for fMRI of the Brain (FMRIB), Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK.
Rebecca S
RS
Millington
National Hospital for Neurology and Neurosurgery, London, UK.
Merle
M
James-Galton
National Hospital for Neurology and Neurosurgery, London, UK.
Mari N
MN
Maia Da Silva
National Hospital for Neurology and Neurosurgery, London, UK; Moorfields Eye Hospital, London, UK.
Gordon T
GT
Plant
Oxford Centre for fMRI of the Brain (FMRIB), Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK.
Holly
H
Bridge
D000368:Aged; D001284:Atrophy / Q000209:etiology; D003337:Corpus Callosum / Q000000981:diagnostic imaging; D038524:Diffusion Magnetic Resonance Imaging; D005260:Female; D007839:Functional Laterality; D006624:Hippocampus / Q000000981:diagnostic imaging; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D019636:Neurodegenerative Diseases / Q000150:complications*; D009778:Occipital Lobe / Q000473:pathology*; D010100:Oxygen / Q000097:blood; D010468:Perceptual Disorders / Q000000981:diagnostic imaging* / Q000209:etiology*; D058609:Visual Field Tests; D014794:Visual Fields / Q000502:physiology*
D010100:Oxygen
Hemianopia; Magnetic resonance imaging; Occipital lobe; Posterior cortical atrophy; Visual dysfunction