Further studies on hereditary unilateral deafness.

Abstract

In a study of 122 children and adolescents with unilateral total deafness, the author tried to elucidate the hereditary aspects of this disease. This has not been done previously. By means of questionnaires information was obtained on the hearing of 2194 relatives of the probands. A total of 165 who confirmed that they were suffering from hardness of hearing or deafness were examined. In 122 the hardness of hearing represented the ordinary sequelae of otitis, occupational deafness, or presbycusis. The remaining 43 cases of hearing impairment were due to endogenous perceptive disease of varying, but predominantly severe degrees, involving one or both ears. Among these families unilateral deafness and deaf-mutism occurred about 6 times and endogenous partial neurolabyrinthopathy about 11 times more often than in the normal population.Investigation of 205 relatives said to have normal hearing revealed 16 subclinical cases of neurolabyrinthopathy, i.e. almost 8 times the manifest cases.None of the parents of the 122 children were blood relations.It is concluded that unilateral deafness is of hereditary nature in 25-30 %, that it is transmitted by irregular dominance, but that it does not make up a genetic entity.