NONSYNDROMIC HEARING-LOSS - AN ANALYSIS OF AUDIOGRAMS

We examined features of the audiograms of 136 individuals, from 28 families, affected by nonsyndromic genetic hearing loss. There were 83 (12 families) with autosomal dominant (AD) loss, 50 (15 families) with autosomal recessive (AR) loss, and 3 (1 family) with X-linked recessive loss. The main audiogram shapes found were sloping (50.3%), residual (26.5%), and flat (21.0%). Specific shapes (ascending and U-shaped) only occurred in 3.7% of AD cases. Audiogram shapes were found to be significantly different between AD and AR families, and showed intrafamilial and interfamilial variability. In the AR group, the main shapes were residual and sharply sloping, and in the AD group, sharply sloping, flat, and gently sloping. There was a significant difference in the degree of hearing loss between AD and AR types, with AD being milder than AR. It has been shown that there is more marked intrafamilial variation in the degree of hearing loss in AD families than in AR ones. The results suggest that the audiograms of nonsyndromic hearing loss are usually nonspecific and that counseling of family members would be better based on the specific family's condition rather than on group information.