右手書字で出現した鏡像書字について

ON A CASE OF MIRROR WRITING WITH THE RIGHT HAND

I．はじめに

　鏡像書字（mirror writing, Spiegelschrift, ecriture enmiroir，—以下MWと略す）は日常の臨床における書字検査の際にしばしば経験される症状であるが，そのほとんどすべては病前に書字の習慣のなかつた左手によつて出現するものである。すでにわれわれは，このようなMWについて，106例の脳損傷例群をできる限り無選択的にとり，それについて左手書字を組織的に検査して臨床＝統計学的分析を行い（浜中他，1978），右利きで左半球の脳内血腫手術後長期間に渡つて左手によるMWの出現を見た症例を通じて若干の実験的な検査を行い（波多野他，1978），MWをめぐる諸問題につき文献的展望を行つた（波多野他，1979）。ここに新たに報告するのは，病前右手によつて書字を行つていた右利き者が，脳硬塞後に右手書字でMWを行い，しかも後になつては左手書字でもMWが出現したという文献的にも極めて稀であると思われる症例についてである。

A case of multiple brain infarction was reported. The patient showed severe psychic symptomes; mild right hemiparesis; non-fluent aphasia; numerous apraxic symptomes, etc. He was right-handed but tried to write at first with the left hand on account of his right hemiparesis. About a month later after the attack, we examined his ability to write figures from 1 to 9 serially. He could write arabic figures from 1 to 9 correctly with his left hand. After that, he wanted to try the same task with the right hand because the motor disturbance was well improved; he wrote three figures in mirror fashion (4, 5, 6-5 partially) and the rest figures correctly but very clumsy with some remarkable perseverations.

In the previous medical literature we could find at least two adult cases of mirror writing with the right hand : Buchbald (1878) and Heilbronner (1910). Herrmann and Pötzl (1926), who studied the problem of writing direction and refered to Heilbronner's case, presented a hypothesis for a mechanism of this phenomenon by the assumption of two Richtungszentren in both parietal lobes. We reviewed this association-psychological hypo-thesis critically because of the mechanical nature of this hypothesis.

Our case resembled Buchwald's one. Before the appearance of mirror writing with the right hand Buchwald's patient had used only his left hand to write for a half year. Therefore we considered that this phemomenon in our case was an expression of the influence of the preceding normal writing with the left hand; it could be also regarded as a manifestation of the perseverative tendency which was remarkable at that stage in our case.

Finally, the possibility to explain this phenomenon by the automatism of writing and some problems about the mechanism of mirror writing with the right hand were discussed in detail.