純粋失書を呈した左視床出血の2例

Two Cases of Pure Agraphia Developed after It. Thalamic Hemorrhage

　脳血管障害による視床病変で純粋失書を呈した症例は従来ほとんど報告されていない。我々は左視床出血後純粋失書を呈した2例を経験したので報告した。〈症例1〉49歳男性，右利き，高校中退。〈症例2〉48歳男性，右利き，中卒。2例共，初期には軽度の聴理解障害，喚語困難などがみられたが，これらの症状は急速に改善し，失書のみを残した。症例1の書字では新造文字および無形態文字が多く，字性錯書もみられ，また保続も強かった。症例2では字性錯書はみられたが，新造文字はほとんど現れず，文字想起不可が多かった。どちらも漢字より仮名の方がやや強く冒されており，また失書に対し「左手だから書けない」とやや病態失認的な傾向がみられた。2例とも慢性期のCTでは大脳皮質には特に異常は認められなかったが，¹²³I-IMP SPECT（early image）では左大脳皮質の血流量低下が示唆された。これまでの純粋失書報告例との検討およびSPECT所見よりこの2例の失書の発現には左大脳皮質の機能低下の関与が大きいのではないかと考えられた。

We have observed two cases suffered from left thalamic hemorrhage, that showed pure agraphia. The first case was a 49 year-old, right handed male, who was educated through 11th grade. The CT scan revealed left thalamic hemorrhage with ventricular casting. The second case was a 48 year- old, right handed male, who was educated through 9th grade.The CT scan reveald left thalamic hemorrhage which is smaller than that of the first case, without intraventricular rupture.

With a standard neuropsychological evaluation performed at chronic stage, neither cases showed oral language disorder, apraxia and agnosia. On the Wechsler Adult Intelligence Scale, total IQ of the first and second case were 71 and 80 respectively. Each case developed severe writing disorder. The first case showed severe neographism and scrawl, mild literal paragraphia, which were frequently accompanied with perseveration. The second case showed literal paragraphia and no respone, but neographism was not detected. The common char-acteristics of both cases were ; 1) intact copy writ-ing. 2) discrepancy between difficulty in writing "Kana" and that in "Kanji". 3) anosognosia of agraphia.

The cerebral blood flow study by 123I-IMP Single photon emission computed tomography revealed low perfusion of the left cerebral hemisphere in both cases. From these findings, we concluded that dysfunction of the left cerebral cortex is responsible for producing agraphia in these cases.