聴力障害にて発症した両側被殻出血の1例—いわゆるcortical deafnessについて

A Case of Cortical Deafness with Bilateral Putaminal Hemorrhage

I．はじめに

　聴覚中枢の損傷で生ずる聴力障害はcortical deafness（皮質聾）と呼ばれ，一般に両側の側頭葉の障害によると考えられている．しかしこれまでこのような報告例は少なく，その病態あるいは責任病巣を含め不明な点が多い．今回著者らは7年前に右側被殻出血に対する皮質経山の血腫除去術の既往歴を有し，その後突然の聴力障害にて発症した左側被殻出血の1例を経験した．本病態を生じた責任病巣およびこれらcortical deafnessの概念とその臨床的問題点に対し若干の文献的考察を加えたので報告する．

A 56 years old right-handed female, a housewife, had suffered from right putaminal hemorrhage which had been treated surgically in July, 1985. Since it was diffi-cult to approach the trans-sylvian fissure, evacuation of the hematoma was performed transcortically through the superior temporal gyrus. She was neurologically free and lived normally until she suddenly became completely deaf in April, 1991. On admission, she was alert, well oriented and spontaneously stated that she was deaf. She showed no response to verbal commands or loud noises but followed complex written commands. No other neurological deficit was observed. In addition to an irregular low-density area in the right temporal lobe, CT scan revealed a left putaminal hemorrhage. Audiological testing disclosed pure tone threshholds to be below 90db on both sides. Auditory brain stem response (ABR) showed waves I to VI in normal latency ranges, but wave VII was not observed. She was treated conservatively. Although her hearing loss had been gradually improving for 1 month, she suffered from word deafness, an inabil-ity to comprehend speech, for the following 2 months. Clinical features, CT findings as well as results of ABR suggest that hearing loss observed in this case, cor-tical deafness, was presumably due to bilateral damage of acoustic radiation of the temporal lobe. It was also suggested that, although she was asymptomatic, cortical and subcortical damage to the right temporal lobe fol-lowing evacuation of the putaminal hematoma may have been extensive. During surgical procedures for evacua-tion of the putaminal hematoma, it has to be always kept in mind not to damage the auditory cortex and its radia-tions.