右半球に脳動静脈奇形を有した右利き交叉性失語症の2症例—その側性化について

CEREBRAL LATERALIZATION IN Two CASES OF CROSSED DEXTRAL APHASIA WITH RIGHT:HEMISPHERE ARTERIOVENOUS MALFORMATION

　抄録　右半球脳動静脈奇形（AVM）からの脳内出血により失語症をきたした2症例を報告した。いずれも生来から右利きである。症例1は60歳の男性で，血縁者に左利きは無い。左片麻痺と意識障害にて発症，右頭頂葉のAVMを血腫と共に全摘出した。聴覚的ならび視覚的理解に改善をみたが，構音失行の強い運動失語症が持続した。症例2は38歳の男性で，姉にひとり左利きがいる。左不全麻痺と意識障害にて発症，血腫と共に右頭頂葉のAVMを全摘出した。術後に麻痺の消失をみたが，左同名性半盲と失名詞失語ならびに失書・失読を残した。これら2症例は，右半球に先天性の疾患であるAVMを有した。また幼少より右利きであって，書字技能も右手によって習得されていた。これらのことにもかかわらずなお右半球に言語機能が存在したこととの関連で言語機能の側性化について若干の考察を加えた。

This paper reports two cases of crossed dextral aphasia.

The first patient was a 60-year-old right-handed male with no family history of sinistrality. He experienced sudden onset of left hemiplegia and loss of consciousness. A CT scan showed high-den-sity area in the right fronto-parietal region. An angiography revealed an arteriovenous malforma-tion (AVM) in the right parietal lobe. It was fed by a branch of the middle cerebral artery and drained through a cortical vein. Neuropsycologicalexamination one week after the surgery showed severe defects of all language moderalities. He was alert and cooperative, but completely mute. He recognized common words by auditory and visual stimuli, but could not perform simple com-mand. He wrote some meaningless letters when asked to write his own name. Auditory and read-ing comprehension gradually improved therafter, but Broca's type of aphasia with non-fluent hesitant and effortful output was still present four months after the surgery.

The second patient was a 38-year-old right-handed male. All members of his family are right-handed except for one sister who is left-handed. He suddenly suffered left hemiparesis and loss of consciousness. A CT scan disclosed a right parietal intracerebral hematoma. And an AVM which was fed by the angular artery and drained through a cortical vein was angiographi-cally demonstrated in the same area. Postopera-tively the left hemiparesis rappidly disappeared, but left homonymous hemianopsia and anomie type of aphasia still persisted. His speech was fluent and daily communication was possible in spite of circumlocutory paraphasic output. Auditory com-prehension of long sentences was impossible be-cause of reduced auditory retention span. His script was clear and fluent, but his writing was restricted to simple grammatical forms with omis-sions and substitutions of letters.

In spite of acquisition of writing and other skillful manipulatory functions by the right, these two patients developed language dominance in the right hemisphere where AVM existed with sur-rounding hypoperfusion in the parietal area. These data suggest that hemispheric language dominance are predetermined by some independent intrinsic factors.