Speech arrestと"純粋"失書

SPEECH ARREST AND"PURE"AGRAPHIA

I．はじめに

　Penfieldら^15,16,17）は，人間の大脳皮質刺激実験で発声および言語停止がRolandic motor areaおよびsuperiorfrontal area （supplementary motor area）と関係があることを確証した。筆者らは左前頭葉腫瘍の2症例に言語停止発作（speech arrest）を認めた。その1例では自発書字，書取および写字などの書字機能が障害されていたが，その他の言語機能は正常範囲であつたのでいわゆる純粋失書を呈するものと考えた。これに対して，他の1例では言語停止発作のほか書字機能などの障害は認められなかつたので，両者の病巣部位について検討した。純粋失書はExnerの書字中枢（左第2前頭回脚部）の損傷に起因するという諸家の報告がある。この点について，言語停止発作ならびに純粋失書を呈した症例と，前者のみを示した症例の責任病巣の差異について検討し，また，左第2前頭回を中心とする損傷による失書の出現機構に関し考察した。

This paper intends to analyse two cases of speech arrest. The patients suffer from the frontal tumor which affects supplementary motor area. The first case is accompanied with"pure"agraphia.

Case 1 A 32 year-old right handed male has speech arrest and"pure"agraphia. Spontaneous speech, naming, repetition and reading are not impaired. Radiographic (C.A.G., CT scan) and surgical localization check is attempted in the paramedian left frontal lobe which controls supple-mentary motor area and a solid tumor nodule of about 1.5 by 2cm in size is detected at the base of the left second frontal convolution (F₂).

It is recorded that writing disturbances continue to one month and half before the tumor is removed. He can not write his signature, spontaneous writing, dictation and copying. After the partial excision of the solid tumor nodule at the base of left F₂, both speech arrest and writing disturbances are improved. Apraxia and agnosia are not noticed.

Case 2 A 26 year-old right handed male has speech arrest only. Speech and writing functions are not impaired. He is intellectual. An oligo-dendroglioma is shown in the left frontal lobe which affects supplementary motor area but the lesion is not extended into the left second frontal convolution.

In both cases, speech arrest is"total"type according to Arseni's subdivision, and verbal repetition does not appear. We have realized that the lesion in the supplementary motor area causes speech arrest and that the left F₂ causes"pure" agraphia. We compare our result with similar cases in the former literature, especially with "pure"agraphia cases caused by the lesion in Exner's writing center.

We conclude that"pure"agraphia can be classi-fied under the category of autonomic-kinesthetic disorders in writing functions caused by frontal lobe lesion.