Selective Disconnection of Specific Visual Association Pathways in Cases of Alzheimer's Disease Presenting with Balint's Syndrome

Abstract

During a recent clinical and neuropathological evaluation of a large autopsy population of brains our attention was drawn to a subset of patients with Alzheimer's disease (AD) presenting with a major impairment of visuospatial skills referred to as Balint's syndrome. In this subset a shift in the distribution of certain pathological profiles had occurred in that the visual areas of the occipital and posterior parietal regions had an increased number of lesions, whereas the prefrontal cortex had fewer lesions than usually observed in AD. Previous quantitative analyses have shown that generally in AD, primary sensory cortical areas are less damaged than association areas of the frontal and temporal lobes, as demonstrated by the laminar and regional distribution of two neuropathological features of the disease, neurofibrillary tangles and neuritic (senile) plaques. The distribution of pathological lesions in the AD cases with Balint's syndrome revealed that specific visual association pathways were disrupted, which are normally spared in AD. These data suggest that in some cases of AD, the particular psychological and neurological symptomatology may be caused by the selective loss of specific corticocortical systems, as reflected in the differential distribution of the neuropathological markers of the disease.

Perception of coherent motion in random dot displays by pigeons and humans

“…Saito (1993) has shown that human performance in direction discrimination as a function of coherence is closely matched by directional response functions of type D cells in the dorsal part of area MST. Finally, some recent studies with Alzheimer patients (e.g., Hof, Bouras, Constantinidis, & Morrison, 1989;Trick & Silverman, 1991) suggest that the decreased motion sensitivity (i.e., the strongly elevated coherence thresholds) of these patients is due to disruption of the occipitoparietal pathway. Taken together, these results indicate that areas MT and MST playa crucial role in the spatiotemporal integration of motion signals.…”

Regional Distribution of Neurofibrillary Tangles and Senile Plaques in the Cerebral Cortex of Elderly Patients: A Quantitative Evaluation of a One-Year Autopsy Population from a Geriatric Hospital

“…In particular, a careful analysis of such cases revealed that in this population, the hippocampal formation systematically displayed a moderate to severe involvement, whereas the neocortical areas were unaffected or showed very low densities of NFTs and SPs Arriagada et al, 1992a ;Berg et al, 1993;Bouras et al, 1993). This difference in regional lesion distribution distinguishes these elderly nondemented cases from the Alzheimer's disease population, in which neocortical areas are devastated (Pearson et al, 1985;Lewis et al, 1987;Hof et al, 1990aHof et al, ,b, 1992Bouras et al, 1992). Most of the recent clinicoanatomic analyses of brain aging have been based on relatively small patient samples consisting of selected cases (Crystal et al, 1988;Katzman et al, 1988;Hubbard et al, 1990;Morris et al, 1991;Price et al, 1991;Arriagada et al, 1992a,b;.…”

“…In fact, Hyman and colleagues have demonstrated that the presence of NFTs in layer II of the entorhinal cortex was correlated by the presence of pathologic profiles in the termination zone of the perforant pathway in the outer portion of the molecular layer of the dentate gyrus, implying that this cortical pathway is severely affected in Alzheimer's disease cases (Hyman et al, 1988). In addition, the distribution of NFTs and SPs in the neocortex and in the hippocampal formation suggests that SP formation may involve the terminal arborization of NFT-bearing neurons (Pearson et al, 1985;Rogers and Morrison, 1985;Lewis et al, 1987;Hof and Morrison, 1990;Hof et al, 1990a;Senut et al, 1991;De Lacoste and White, 1993).…”

Ocular and Visual Manifestation of the Alzheimer’s Disease: A Literature Review, Part I: Animal Models and Human Pathology

“…This suggests that selected cortical pathways linking the primary visual regions to the posterior parietal and cingulate visual association cortex may be involved in the early stage of the AD. Hof et al (37) found an increased number of lesions in the visual areas of the occipital and posterior parietal regions in AD patients presenting with Balint's syndrome. Similarly, using positron emission tomography (PET) in patients with the visual variant of AD, Pietrini et al (38) and Nestor et al (39) found selective hypometabolism in the occipitoparietal regions.…”