Abstract
In 1965, a mysterious illness, diagnosed chronic organic mercury poisoning, began to affect the inhabitants, especially fishermen, farmers and their families, who lived in around the mouth area of river AGANO, situated in suburbs of Niigata city, Japan. They had taken ocasionally at table fishes and shelfishes, which were contaminated with mercury compounds, products of chemical manufacturing processes.
25 cases of them were investigated otologically and audiologically. And 14 cases were pointed out some audiological disturbances. The peculiar findings of them: 1) outwardly normal or very little hearingloss in pure tone audiometries at least in early stage, 2) pure tone thresholds appeared to be unsettled in a few cases, 3) speech articulation score were growing worse in spite of normal pure tone thresholds, 4) in middle stage, pure tone thresholds became to worse slowly at all frequencies or at high frequencies and speech intelligibility functions became systematically poorer, 5) recruitment (SISI and others) were negative in all cases except 4 cases of inner ear deafness, 6) Békésy audiometries (T. T. S) showed two types, unsettled wide amplitude and severe abnormal adaptation characterizing the type III pattern.
As above mentioned, hearing impairment of chronic organic mercury poisoning was revealed to be retrocochlear disturbance, especially cortical deafness.
