C Rainsard | PubMed Health

PubMed1985

Cortical atrophy in senile dementia of the Alzheimer type is mainly due to a decrease in cortical length.

A prospective study was undertaken to select mentally normal old subjects and patients with senile dementia of the Alzheimer type (SDAT). The test score of Blessed et al. (1968) (BTS) was used to determine the severity of mental impairment. A pathologic study confirmed the diagnosis of either SDAT or normal brain aging at postmortem examination in 12 cases. The cortical area and the cortical perimeter of the different cerebral lobes were measured on 1-cm-thick coronal sections using a semiautomatic image analyzer. Cortical length and thickness were calculated using perimeter and area values. BTS was significantly correlated with both the area (r = 0.7695, P = 0.003) and the length (r = 0.7421, P = 0.006) of the temporal cortex. There was no significant correlation between BTS and thickness of the temporal cortex (r = 0.559, P = 0.059). These results show that reduction of length is one of the major determinants of cortical atrophy. Although this has to be confirmed by histological study, they favor the hypothesis of a column-selective atrophy in SDAT which should be considered in the interpretation of the microscopic data.

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Fibre disorganization in the neocortex of patients with senile dementia of the Alzheimer type.

The loss of neurons, which is thought to occur during senile dementia of the Alzheimer type, could alter the fibre organization of the neocortex. In the present study, the density and course of the fibres were measured in histological sections in 14 cases: all were women over 75 years of age who had been living in a long-stay hospital and had been prospectively assessed by the test score of Blessed et al. (1968). Their intellectual status ranged from nearly normal to severely demented. Samples from the supramarginal and prefrontal gyri were studied after Bodian's impregnation. The course of the fibres in 3-dimensional space was determined by two angles: (a) the angle which characterized their orientation in the plane of section and discriminated between horizontal (tangential), vertical (radial) and oblique fibres and (b) the angle of section with which the fibres were cut. The total density of fibres correlated neither with the test score nor with the density of neurofibrillary tangles or senile plaques. The percentage of obliquely orientated fibres and of fibres with a high sectioning angle increased in the course of the disease. This increase was mainly at the expense of the horizontal fibres in the supramarginal gyrus and could be explained by the presence of a great number of small, tortuous and abnormally orientated fibres (kinked fibres) in the most severely affected cases. The methodology employed in this study could be useful in the investigation of fibre architecture in other diseases involving the cerebral cortex.

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