皮質ろう (cortical deafness) の1例 -両側側頭葉損傷による聴覚障害-

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A 50-year-old, right-handed, male showed cortical deafness and Wernicke's aphasia after 14 hours' duration of atrial paroxysmal tachicardia.
Neuroradiological study by ⁹⁰Tm brain scan revealed hot lesions in the temporal area bilaterally and CT scan showed that a low-density area occupied in the both temporal gyri and insulas. The basal ganglia and thalamus (including medial geniculate bodies) were spared bilaterally.
1) Pure tone audiometry revealed a bilateral mild hearing loss but the thresholds were unstable.
2) Békésy audiometry showed a temporary threshold shift bilaterally.
3) Speech audiometry revealed lower discrimination rate than 25% bilaterally.
4) Discrimination rate of musical instruments was remarkably low. Perception of rhythm and melody was markedly impaired.
5) Sound localization for warble tone was well preserved.
6) Auditory Brain Stem Response by click sounds was normal.
7) Wave forms of the middle latency response were almost normal.
However, thresholds of the slow vertex response were abnormally high in both ears. Thus, auditory pathway in the peripheral apparatus and brain stem appeared to be almost intact, but functionally, cortical or subcortical lesions were suspected bilaterally, Sensory aphasia was coincident. Other six cases of cortical deafness or auditory agnosia in the literature were reviewed, and the clinical findings and auditory disorders of these seven cases were remarkably similar to those of the case reported herein. In conclusion, we consinered that “auditory agnosia due to bitemporal lesions” for these cases was the better term “cortical deafness.”