The patient was a right-handed boy. Pregnancy and delivery were normal. There were no neonatal complications. His development was normal until the age of 6 years and 10 months when he suddenly fell into coma. He was admitted to a hospital, where he was diagnosed as having encephalopathy of unknown cause. It was found that he did not respond to verbal stimuli after recovery from coma. He was referred to our hospital for detailed examination of hearing at the age of 7 years, and received neuroradiological and audiological examinations including X-ray CT, positron-CT, behavioral audiometry, auditory evoked response audiometry as well as other hearing and speech tests. Pure tone audiometry showed that auditory thresholds for pure tones ranging from 125 to 8,000 Hz were normal, while speech audiometry demonstrated that he was unable to discriminate test words. However, he accurately recognized environmental sounds and noises as well as sounds produced by musical instruments. The decreased uptake of 11C-glucose at the left temporal lobe was demonstrated by positron CT, although no abnormality was showed by X-ray CT. WISC-R showed he had normal intelligence. ITPA demonstrated that the psycholinguistic ability via visual channel remained intact, whereas auditory memory and auditory closure were markedly impaired. The boy had no difficulties in reading, naming and writing. Speech therapy was started as soon as diagnosis of word deafness was made. Until 6 months after onset, he never understood and repeated what was said to him.(ABSTRACT TRUNCATED AT 250 WORDS)