Pathogenesis of Dementia in the Elderly

Analysis Based on the Involutional Changes and the Vascular Lesions of the Brain

Abstract

Pathogenesis of dementia was investigated through quantitative analysis of the involutional changes and the vascular lesions of the brain in 146 consecutive autopsy cases over the age of 49 years (ranging from 50 to 92, with mean 73.3 in years). The subjects, who had been admitted to the Department of Geriatrics, University of Tokyo Hospital and Harunaso Hospital for chiefly physical diseases, were divided clinally into four groups; the demented (61 cases), the non-demented (55), the borderline (19), and the rest (11) in whom insufficient informations were available on the intellectual capacity.
As to the involutional changes, number of Alzheimer's neurofibrillary changes (NF), senile plaques(SP), and the vessels involved into amyloid angiopathy (AA) was counted respectively in the 6μ-thick specimen of the hippocampal region through thioflavine T fluorescence microscopy. The patients with involutional changes over certain level (NF≥101, SP≥101, or AA≥1 over the whole specimen) mostly belonged to the demented group (7% of the non-demented, and 60% of the demented).
Vascular lesions were examined through serial cutting of the brain, and all the lesions visible to the naked eye were recorded. According to the comparative study of demented and non-demented patients, the important influence of the site, size and numbers of the lesions was evident. Those who showed vascular lesions over a certain level (multiple small lesions or middle- to large-sized lesion (s) in the central region or cortical areas of the left hemisphere) were exclusively included in the demented group (6% of the non-demented, and 58% of the demented).
Since mots of the patients with two kinds of the organic changes beyond the extent described above belonged to the demented group except for the border ine cases (13% of the non-demented, and 93% of the demented), such changes probably represent the cause of dementia in the elderly. Thus, 93% (57 cases) of the demented were divided into three subgroups according to their predominant anatomical changes; involutional type(21 cases), vascular type (20), and mixed type(15) consisting of marked degrees of these two.
Then clinical data were compared among these subgroups. Of the various manifestations of mental defects (wandering, trifling with feces, hallucinations, night delrium, etc.) none was specific to any one of three types of dementia, except for emotional incontinence which was significantly more frequent in vascular type than in the other two. The frequencies of several neurological signs (diplegia, dysarthria, dysphagia and aphasia) were similar between vascular type and mixed one, and were significantly higher than those in involutional type. Thus, in spite of some similarity to involutional type in some mental features, mixed type resembled vascular type as to several neurological manifestations, indicating a difficulty in clinical differentiation of this type of dementia from the other two.