Balint's syndrome in Alzheimer's disease: specific disruption of the occipito-parietal visual pathway.

Previous quantitative neuropathologic analyses have shown that the association cortices of the temporal and frontal lobes are more damaged than the visual regions of the occipital lobe in Alzheimer's disease. In the present paper, we report on a subpopulation of Alzheimer's disease patients presenting a visual defect referred to as Balint's syndrome, and displaying a global caudal shift in pathology. Balint's syndrome is a defect in visuospatial skills, and the distribution of pathology suggests that the connections underlying this functional component of the visual system are devastated, whereas they are normally spared in Alzheimer's disease. These results suggest that multiple subtypes of Alzheimer's disease exist with differential distribution of pathology and corresponding neurologic symptomatology, and that neuritic plaque and neurofibrillary tangle formation involve the loss of specific corticocortical projections associated with specific functional deficits and identifiable neurologic syndromes.