Mild amyloid pathology in the primary visual system of nonagenarians and centenarians

In order to study the patterns of Alzheimer disease (AD)-related pathology in the primary visual system of the oldest old, we performed a quantitative analysis of senile plaques (SP), diffuse beta amyloid (A beta) deposit and neurofibrillary tangle (NFT) distribution in primary area 17, and a semi-q uantitative analysis in the dorsal lateral geniculate nucleus (LGN), latera l inferior pulvinar (LIP) and superior colliculus (SC) of 21 individuals ag ed between 93 and 102 years. Among them, 10 cases were considered as non-de mented (ND), while 9 presented very mild cognitive impairment (VMCI), and 2 cases had a clinical diagnosis of AD. Silver methenamine and Gallyas stain ing, A beta and tau immunostaining revealed the distribution of AD lesions. In primary area 17, most cases, either ND or with VMCI displayed a low to medium number of SP. There was no significant difference in SP and A beta d eposit densities between ND and VMCI groups. On the whole, 0.4-2.4% of the cross-sectional cortical area was covered with A beta deposits. Only 6 case s, either ND or with VMCI, were totally devoid of SP and diffuse AP deposit s. Among the subcortical structures, the LIP and SC exhibited low densities of SP and A beta deposits in about half of the ND and VMCI cases, while th e LGN was totally spared. NFT were almost absent in area 17 and subcortical nuclei of ND and VMCI cases. These data imply that the ageing of the prima ry visual system in ND and VMCI nonagenarians and centenarians is character ised by the frequent development of mild amyloid pathology in area 17 in th e absence of NFT. In agreement with previous studies in very old cohorts, t hey also suggest that amyloid deposition is not related to the early stages of the dementia process in the oldest old. Copyright (C) 2001 S. Karger AG , Basel.