Hyperlexiaおよびambient echolaliaに対して反響誘発試験を行った脳梗塞の1例

Echo Induction Test for Hyperlexia and Ambient Echolalia in a Case with Cerebral Infarction

要旨：Hyperlexiaおよびambient echolaliaの報告は稀であり，それらの経過を調べた報告はない．今回我々は69歳女性で左前部帯状回および脳梁に病変のある脳梗塞症例に対して反響誘発試験を試み，hyperlexiaおよびambient echolaliaの経過を調べたので報告する．本症例は失語症および認知症はなかったが，視覚性探索反応，右手の道具の強迫的使用，脳梁離断症候群を認めた．最も特徴的な現象としてhyperlexiaおよびambient echolaliaを認めた．この症例に対し脳梗塞発症1カ月，2カ月および6カ月後に，目の前に本棚を設置することによる視覚刺激と擬似院内放送を流すことによる聴覚刺激の2つの条件下でそれぞれ10個の口頭質問を行い，hyperlexiaおよびambient echolaliaの誘発の有無を調べた．Hyperlexiaは発症1カ月および2カ月後に誘発されたが，ambient echolaliaは発症1カ月後にのみ誘発された．本症例のhyperlexiaおよびambient echolaliaが，左前部帯状回および脳梁損傷による外部刺激に対する脱抑制反応が軽減したことに伴い，消失に転じた可能性が考えられた．

Abstract : Hyperlexia and ambient echolalia are rare conditions, and investigations into their clinical course have not been reported in the literature thus far. Here we report the case of a 69-year-old woman with cerebral infarction of the left anterior cingulate cortex and corpus callosum, on whom we performed an echo induction test for studying her long-term hyperlexia and ambient echolalia. Her clinical features included symptoms of complex disorders such as visual groping, compulsive manipulation of tools and callosal disconnection syndrome. The patient did not have dementia or aphasia. Her most outstanding behavioral traits were the hyperlexia and ambient echolalia. We investigated the induction of her hyperlexia and ambient echolalia by subjecting the patient to 10 verbal questions using a background of visual (bookshelves were placed in front of her) and auditory (imitated hospital announcements) stimuli at periods of 1, 2 and 6 months after the stroke. Hyperlexia was induced at 1 and 2 months after stroke, whereas ambient echolalia was only induced at 1 month after stroke. The disappearance of the hyperlexia and ambient echolalia in this case might be due to a reduction in the disinhibition of response to external stimuli caused by damage sustained in the stroke to the left anterior cingulate cortex and corpus callosum.