[Etiology of moderate and profound deafness in childhood]

The present study sought to determine the etiology of bilateral profound hearing losses in children living in Germany. Additionally, a comparison with the data of previous investigations in the available literature was used to update causes now known through medical progress.

The medical charts of 314 profoundly hearing-impaired pupils at schools for the deaf in Cologne, Germany, were reviewed. All available data on possible etiological factors were collected. In addition, the families of these children were interviewed using a standardized questionnaire.

Sixty children were found to have bilateral sensorineural hearing losses averaging 30 to 60dBHL within the frequency ranges of 500-2000 HZ, while 254 had bilateral hearing impairments of 60 dBHL or greater. The etiology of the hearing disorder could be determined in 218 of the children. Eighty-two children suffered from hereditary deafness and 136 from acquired hearing losses. The etiology could not be determined in 96 children. Hereditary causes included 34 children with mendelian autosomal dominant losses, 46 with autosomal recessive losses and two children with genetic but non-mendelian causes. Immigrants to Germany (mostly from Turkey and the former Soviet Union) were found significantly more frequently among the students of these schools, than among the total population of the Cologne area. In this group of students, autosomal recessive deafness was particularly common as compared to the overall native population. Acquired hearing disorders were broken down into three subgroups: prenatal, perinatal and postnatal disorders. A prenatal etiology was considered in 32 children, 21 of whom had known congenital rubella infection. This entity was significantly less common among younger children. A perinatal etiology was considered in 60 children. Causative factors were birth asphyxia, apnea and/or hyperbilirubinemia. Forty-four children had deafness attributed to postnatal causes, with bacterial meningitis (n = 31) being the most important single factor. The findings reported indicate changing trends for causes of hearing loss in children with severe hearing impairment in Germany.