Audiometric identification of normal hearing carriers of genes for deafness.

Abstract

As most carriers of genes for recessive deafness do not display hearing impairment to a greater extent than average, it is impossible to identify suspected gene carriers by ordinary audiometry. In the study reported here more advanced test methods, namely Bekesy audiometry and the stapedius reflex test, have been applied in an attempt to detect any subclinical peculiarities in the hearing; the material consisted of a group of 30 parental pairs with normal hearing and a strong indication of genetic deafness; they had 74 children, 47 of them with severe genetic hearing impairment or total deafness. On comparison with a control group, two peculiarities were found in the hereditary series, namely small but distinct dips in the middle frequency range of the hearing threshold, and abnormally high thresholds for the acoustically elicited stapedius reflex.The observations are discussed against the background of earlier genetic and histologic findings.