PATHOLOGY OF SUBCORTICAL VISUAL CENTERS IN RELATION TO CORTICAL DEGENERATION IN ALZHEIMERS-DISEASE

Subcortical visual centres such as the lateral geniculate nucleus, the lateral inferior pulvinar and the superior colliculus, together with the primary visual cortex and its adjacent white matter, were studied in 12 AIzheimer brains and five age-matched controls. The periodic aci d methenamine technique was used for the demonstration of senile plaqu es and the Gallyas technique for neurofibrillary tangles and neuritic threads in the neuropil. In the lateral geniculate nucleus and inferio r pulvinar, the presence of periodic acid methenamine-positive senile plaques was observed in variable numbers in all Alzheimer cases. In th e lateral geniculate nucleus, senile plaques were encountered more oft en in parvocellular than in magnocellular layers, in the interlaminar zones, in the optic radiation and in the adjacent pre-geniculate nucle us. Gallyas staining did not reveal any neuro-fibrillary tangles, neur itic threads or neuritic plaques, meaning that in this thalamic region there are mainly amyloid deposits without neuritic degeneration. In t he superior colliculus both amyloid and neuritic plaques, as well as n eurofibrillary tangles and neuritic threads were encountered in the su perficial and deep layers. In the primary visual cortex, all types of senile plaques were observed as well as a rather high number of neurof ibrillary lesions in pyramidal neurons, mainly in layers 5 and 6, but also in several types of non-pyramidal neurons. In the underlying whit e matter there was a morphologically heterogeneous population of neuro fibrillary tangle-bearing neurons and a considerable number of threads representing degenerating axons, suggesting that degeneration could f ollow corticosubcortical connections. These data demonstrate that lesi ons in the primary visual structures and pathways are more prevalent t han previously observed and could partly explain the visual disturbanc es in Alzheimer's disease.