純粋語聾および聴覚失認を呈した両側側頭頭頂葉病変の一例

A CASE OF PURE WORD DEAFNESS AND AUDITORY AGNOSIA ASSOCIATED WITH BILATERAL TEMPORO-PARIETAL LESIONS

　抄録　症例は，49歳，女性。右利き。1980年9月21日左内頸動脈瘤破裂によるくも膜下出血。発症4日目脳動脈瘤根治術。同10日目V-P shunt術施行後右側頭頭頂葉に皮質下血腫が認められ，翌日血腫除去術。術後意識障害および四肢まひが増強したがこれらは次算に改善し，純粋語聾及び聴覚失認が残存した。耳科学的検査では，外耳・鼓膜・内耳に異常はなく，純音気導聴力・auditory brainstem response・auditoryevoked responseはいずれも正常範囲にあつた。神経心理学的には，口頭表出言語・読字・自発書字・計算はいずれも可能だが，聴覚的言語理解は著明に障害され復唱・書取がほとんど不能で，環境音・楽器音・音楽の認知も障害されていた。これら純粋語襲および聴覚失認に対して疾病否認が認められたが，その他の失行．失認は認められなかつた。CT scanで両側側頭頭頂葉に異常低吸収域が認められた。

　著者らは，聴覚刺激の認知過程について機能的図式を想定し，聴覚刺激は言語性・非言語性にかかわらずあるレベルまでは両側半球で処理されると考えた。本症例の純粋語襲および聴覚失認は，左半球第一次聴覚野と第二次聴覚野との連絡路および右半球第二次聴覚野とが障害されたために生じたものと考えられた。

A-49-year-old right-handed female was report-ed. She showed pure word deafness and auditory agnosia because of bilateral temporo-parietal lesions. The left lesion resulted from angiospasm of the left anterior and middle cerebral arteries after subarachnoid hemorrhage due to a ruptured aneurysm of the left carotid artery, and the right one resulted from subcortical hematoina after the V-P shunt operation. CT scan revealed the abnormal low density area on the bilateral tern-poro-parietal regions seven months after onset.

Neurophychological findings were as follows : there were no aphasic symptoms such as para-phasia, word finding difficulties, or disturbances of spontaneous writing, reading and calculation. But her auditory comprehension was severely distur-bed, and she could neither repeat words after the tester nor write from dictation. She also could not recognize meaningful sounds and music in spite of normal hearing sensitivity for pure tone,BSR and AER.

We discussed the neuropsychological mechanisms of auditory recognition, and assumed that each hemisphere might process both verbal and non-verbal auditory stimuli in the secondary auditory area. The auditory input may be recognized at the left association area, the final level of this mechanism.

Pure word deafness and auditory agnosia of this case might be caused by the disruption of the right secondary auditory area, the pathway be-tween the left primary auditory area and the left secondary auditory area, and between the left and right secondary auditory areas.