非流暢性失語で発症し，左右対称性の大脳変性所見を呈した大脳皮質基底核変性症剖検例

An Autopsied Case of Corticobasal Degeneration with Onset of Nonfluent Aphasia Revealing Symmetrical Cerebral Involvement

はじめに

　病理学的に大脳皮質基底核変性症（corticobasal degeneration：CBD）と診断された症例の臨床表現型は，遂行機能障害と運動障害の合併を呈する一群の頻度が最も高く，他に非流暢性失語，前頭側頭型認知症（frontotemporal dementia：FTD），後部皮質萎縮症を呈する場合もあることが報告されている¹⁾。さらに最近では，進行性核上性麻痺（progresssive supranuclear palsy：PSP）の一臨床表現型であり，姿勢反射障害，早期からの易転倒性，核上性垂直方向性眼球運動障害，左右対称性の運動障害，嚥下障害を主徴とするRichardson症候群の臨床像を呈するCBDの一群が存在することも報告されており²⁾，CBDは臨床的に多彩な症状を呈し得ることが示されている。一方，CBDの原型ともいえる左右非対称性の失行および錐体外路症状を中核とする変性疾患は，臨床的に皮質基底核症候群（corticobasal syndrome：CBS）と呼ばれ，その病理学的背景はCBDを主体としながらも，アルツハイマー病や進行性核上性麻痺，ピック病（ピック小体病）など，種々の変性疾患を含んでいる^3,4)。

　筆者らは，非流暢性失語で発症し画像検査で左右対称性の変性所見を認めたCBDの剖検例を経験し，臨床症状の経過と病理所見の対比について考察した。

Abstract

　Herein we describe a patient with established corticobasal degeneration with onset of nonfluent aphasia and showing symmetrical cerebral involvement. A 64-year-old man with a speech disorder for 2 years visited our hospital. He had nonfluent aphasia (reduced spontaneous speech, loss of intonation, anomia, repetition disorder, and difficulty in speaking short sentences). He also showed right-sided motor neglect, hypertonus of the left lower limb, a mask-like facial expression, and difficulty in closing his eyes. He was restless and walked around even during examination, suggesting frontotemporal dementia (FTD). Single-photon emission computed tomography (SPECT) revealed symmetrical reduction of cerebral blood flow in the bilateral fronto-temporo-parietal lobes. His neurological condition deteriorated gradually and a year later he could not speak comprehensive sentences. Magnetic resonance imaging (MRI) of the head at age 70 showed symmetrical atrophy of the bilateral fronto-temporal lobes. He died of respiratory failure after clinical problems lasting ten years.

　On pathological examination, the fixed brain weighed 1,010 g and showed bilateral symmetrical atrophy of the frontal lobes. Histopathological examination revealed neuronal loss and gliosis in the frontal lobes, especially in the frontal convexity, superior frontal gyrus and precentral gyrus. Gallyas-Braak silver staining showed astrocytic plaques, argyrophilic threads and coiled bodies mainly in the frontal lobes. The substantia nigra showed severe neuronal loss on both sides and presence of free melanin. Pathological diagnosis was corticobasal degeneration (CBD).

　We believe that the patient had nonfluent aphasia and FTD reflected in bilateral degeneration of the frontal lobes. Some cases of CBD may present with symmetrical degeneration of the brain, even though left-hemisphere symptoms such as aphasia reveal themselves at an early stage.

(Received: January 18, 2012, Accepted: March 6, 2012)