Aetiology of hearing disorders in children at the schools for the deaf

Ninety-three children attending the schools for the deaf in Copenhagen were examined in order to assess the aetiology of the hearing disorder and to compare the causing factors to those indicated in a previous investigation from 1953. Based on pre-existing investigations including both audiological and non-audiological procedures, the aetiology of the hearing impairment was known in 63% while in 37% the cause of the hearing disorder was unknown. A thorough examination programme was performed in 71 of the attending children whereby a reduction of 'unknown cause' of the hearing disorder could be obtained in half of these children. Compared to the previous investigation from 1953 the incidence of acquired hearing impairment had decreased in contrast to congenital severe hearing impairment. Based on the results of the present investigation it is concluded that an improved nosological classification can be obtained by re-evaluation of both the children and the parents; the physical examination is a long-standing dynamic process running over years; the increased incidence of congenital hearing impairment can be ascribed to prenatal infections, predominantly foetal rubella which is a preventative disease.