原発性進行性失行

Primary Progressive Apraxia

Ⅰ．原発性進行性失行とその概念

　1982年にMesulam¹⁾は，7年間にわたって全般的認知機能低下をきたさずに進行性の失語を呈した症例を「緩徐進行性失語」として報告した。その後，高次脳機能の要素的な障害（失語，失行，失認など）を認める神経変性疾患が注目されるようになった。「原発性進行性失行」はこの一連の流れの中で出てきた疾患概念であり，古くは1933年のLhermitteら²⁾による報告があるが，以下の2報告以後，「原発性進行性失行（ないし緩徐進行性失行）」として注目されることとなった。

　(1)De Renzi³⁾の報告（1986)　認知症や口頭言語機能の障害なしに視覚認知機能の進行性障害をきたした2例と全般的な失行（口頭命令指示による動作だけでなく，実物品の使用，模倣による動作も困難）をきたした1例を報告した。この症例3が「緩徐進行性失行」と考えられている。

Abstract

　Similar to primary progressive aphasia,primary progressive apraxia has been considered to cause slowly progressive apraxia without dementia and to be a dependent disease.　Of the 3 cases reported by De Renzi in 1986,1 case showed slowly progressive apraxia without dementia.　Since then,cases of primary progressive apraxia have been reported occasionally.　Studies on primary progressive apraxia indicate that not only focal lesions caused by vascular disease or brain trauma but also lesions caused by neurodegenerative disease can cause apraxia alone,thereby supporting the hypothesis that apraxia-associated neurodegeneration may develop in cases of primary progressive apraxia.　The pathogenesis of primary progressive apraxia is yet to be elucidated.　Clinical features of primary progressive apraxia are not precisely distinguishable from those of corticobasal degeneration (CBD); further,previous studies have indicated that the brain pathology observed in primary progressive apraxia is consistent with that in Alzheimer disease (AD) or Pick disease.　"Primary" progressive apraxia may be intrinsically different from slowly progressive apraxia that is associated with CBD,AD,or Pick disease and may show specific pathological findings.　On the other hand,primary progressive apraxia may not be a dependent disease but a syndrome characterized by prolonged neurodegeneration that is observed in various degenetive dementias such as CBD,AD,or Pick disease.