Abstract
One hundred and eleven children with bilateral hearing loss of unknown etiology have been followed up for a period of 1 to 6 years. Audiograms were studied from the view point of progression of hearing loss. Children were classified into 2 groups of 47 hereditary cases and 64 cases with unknown etiology.
The conclusions obtained were as follows.
1, Average hearing level deteriorated slowly during the observation period of 1-6 years. No difference was observed between both groups of the hereditary and unknown. Average deterioration was accounted for about 10 dB in 5-6 years.
2. In 39 cases out of 111 cases (35, 1 % : hereditary group 29.8% and unknown group 39.1%), hearing level detetriorated more than 15 dB.
3. The dominant shape of audiograms in cases with progressive hearing loss was gradually sloping, and in a few cases abrupt shape.
