Epidemiology of hearing loss and aetiological diagnosis of hearing impairment in childhood.

A total of 117 children, 55 girls and 62 boys with a median age of 8 years, range 2-12 years, was retrospectively evaluated in consideration of: (1) the prevalence rate and characteristics of permanent hearing loss (defined as the average of 500, 1000 and 2000 Hz greater than or equal to 35 dB HL on the better hearing ear); (2) the aetiology of the hearing impairment; (3) the basis for the aetiological diagnosis in the individual child, and (4) the value of non-audiological investigations. The overall prevalence of permanent hearing loss was 1.4% in this geographical area (children with recurrent episodes of serous otitis media are excluded). In 91% (106/117) the hearing loss was sensorineural, in 4% (5/117) conductive and in 5% (6/117) mixed conductive/sensorineural. In 63% (74/117) the hearing loss had been confirmed and assessed at the age of 3 years, while in 31% (37/117) the hearing loss was ascertained after the age of 3 years. 85% (99/117) were considered to suffer from congenital/early acquired hearing loss. The aetiology of hearing impairment could be assessed in 73% (85/117) of the children, while 27% (32/117) were diagnosed as 'unknown aetiology'. In 48% (56/117) combined audiological/non-audiological investigations had been performed, resulting in a known aetiology in 86% (48/56). In 52% (61/117) only audiological examination had been performed, resulting in a known aetiology of 61% (37/61). A significant difference (P less than 0.005) in known aetiology between these two groups is present, indicating that additional non-audiological evaluation is of decisive importance in the aetiological assessment of hearing impairment. Based on the present and previous investigations, a routine examination programme is proposed directed towards a systematic evaluation of the symptom of hearing loss and its aetiology with due caution to the individual child. The evaluation should be based on a combination of audiological/non-audiological examinations, which includes a broad interdisciplinary cooperation that preferably should be performed at diagnostic assessment centers.