非痴呆者大脳皮質のアミロイドβタンパクの検討—軽度アルツハイマー型老年痴呆との比較

A Study of Cerebral Amyloid β-protein Deposits in Non-demented Peoples: comparison with those in early stage of senile dementia of Alzheimer type

　【抄録】　非痴呆者の大脳皮質に出現するアミロイドβタンパク沈着（AmD）についての基礎的データを得，その意義を知るために，40歳代から80歳代までの非痴呆剖検例125例と，対照として軽度アルツハイマー型老年痴呆（SDAT）5例について，AmDの出現の有無と程度を，海馬を通るメセナミン銀染色半球切片で第3側頭回，島回，帯状回について検討した。程度はabsent〜severeの5段階で評価した。その結果，AmDは出現頻度，程度ともに老齢化に伴い増加するが，増加率は80歳代で最も高かった。すでに40歳代で少数ながらAmDを示す例がある一方で，80歳代に至ってもなお43.4％が陰性で，80歳代での陽性例のうちsevere例は21.7％であった。なお，severe例でのAmDの程度は軽度SDAT例に匹敵していた。これは，高齢に至ってもAmDを来さない一群があることと，痴呆に至るのはsevere AmD例のうちの一部であることを示している。AmDの形態は老人斑の各亜型に対応しており，AmDが軽度の段階ではびまん性老人斑のみで構成されることが多いが，高度になるにつれて定型老人斑と原始老人斑を伴う例が増加し，軽度SDATでの構成に近づく。

　To study the significance of amyloid β-protein deposits (AmD) in the brains of non-demented individuals, we examined the brains of 125 autopsy cases with age at death ranging from the 5th to 9th decade using methenamine-silver stained sections through the level of the hippocampal region. The 3rd temporal, insular, and cingular gyri were light microscopically examined, and the extent of AmD was assessed with a 5-grade system ranging from absent to severe. The incidence and extent of AmD increased with aging, and the increase was most prominent in those in their 9th decade. A few cases in the 5th decade showed AmD, while 43.5% of those in the 9th decade were free of AmD and 21.7% had severe AmD. These results indicate that some elderly individuals have no AmD and that cases with severe AmD do not always manifest clinical dementia. In addition, most cases with mild AmD presented only diffuse plaques, while all cases with severe AmD had not only diffuse plaques but also typical and primitive plaques. The quantitative and qualitative differences of AmD between non-demented subjects with severe AmD and cases with early stage of senile dementia of Alzheimer type were also discussed.