Logopenic variant of primary progressive aphasia(LPA)—5症例における臨床症状と機能画像所見との関係

Logopenic Variant of Primary Progressive Aphasia(LPA): A clinical study for cognitive syndrome and functional neuroimaging in 5 patients

抄録

　Logopenic variant of primary progressive aphasia(LPA)の診断基準を満たす5症例の神経心理学的症状と脳血流SPECT画像との関係を検討した。全症例で音韻性錯語と左縁上回の血流低下の有無が一致しており，語の理解障害がみられた症例では，上，中，下側頭回の後部に血流低下を認めた。LPAにおける音韻性錯語，語の理解障害の出現には，これらの部位の機能低下が関与していることが示唆された。文レベルの復唱障害や理解障害の重症度は，言語性短期記憶障害の重症度と相関する傾向があった。Logopeniaがみられなかった一部の症例では，被影響性の亢進や保続など前頭葉症状が目立つ傾向があり，前頭葉の機能低下が発話量減少の顕在化を妨げている可能性が考えられた。LPAのいくつかの症状において，局所損傷例の研究で確立された失語の症候学とその病巣局在に関する知見と類似した関係を見出すことができた。LPA症例の多様性の少なくとも一部は，局所損傷例と同様に，機能低下が及ぶ範囲の多様性によって説明できると考えられた。

　We examined the neuropsychological findings and their relationship to regional cerebral blood flow in SPECT studies in 5 patients who met the diagnostic criteria for logopenic variant of primary progressive aphasia(LPA). In all patients, the presence or absence of phonemic paraphasia corresponded to the presence or absence of decrease in blood flow in the left supramarginal gyrus, respectively, which suggested that the occurrence of phonemic paraphasia in LPA is related to functional decline in the left supramarginal gyrus. Patients with impaired single-word comprehension showed decline in the posterior part of the left superior, middle and inferior temporal gyri in functional images. Functional decline in the whole part of the left posterior temporal lobe may be attributable to the impairment of single-word comprehension in LPA patients. The severity of impaired repetition and comprehension of sentences and phrases tended to be correlated with the severity of deficit in verbal short-term memory, which underlined the assumption that attributed the impairment of verbal short-term memory to deteriorated repetition and comprehension of sentences and phrases. Two patients without logopenia showed some frontal lobe syndromes, such as environmental dependency and perseveration. This finding raised a hypothesis that frontal lobe dysfunction prevented the manifestation of reduced speech production, although functional images did not show supporting findings. Some of the neuropsychological symptoms of LPA related to functional decline in particular brain regions, and the relationships were similar to those known in the established symptomatology of aphasia in patients with focal brain damage. In LPA patients, as well as in patients with focal lesion, the variety of regions with functional decline may partly explain the variety of symptoms in the patients.