AUDIOMETRIC PATTERNS OF GENETIC NON-SYNDROMAL SENSORINEURAL HEARING-LOSS

Sixty-five families with non-syndromal sensorineural hearing loss (NS- SNHL) of genetic aetiology were subtyped according to Gorlin el al.(4) Individual audiogram shapes were also classified in order to detect i nter- and intra-familial variations. In 48 families with an Autosomal Dominant (AD) inherited form, 26 exhibited the features of (high-frequ ency) progressive NS-SNHL, 12 those of mid-frequency NS-SNHL, 5 were a ffected by congenital low-frequency NS-SNHL; 1 kindred showed a progre ssive low-frequency pattern and another 1 a unilateral NS-SNHL; only 3 kindreds were affected by severe congenital NS-SNHL. Autosomal Recess ive (AR) inherited forms were composed of 9 kindreds with severe conge nital NS-SNHL, and 7 with moderate congenital NS-SNHL. One X-linked fo rm was identified. AD- and AR-inherited NS-SNHL differed significantly both in severity of hearing impairment and in audiogram shapes. With few exceptions, in each family classified according to Gorlin, most of the affected subjects shared the same audiogram profile, Intrinsic pr ogression of the disease versus ageing was studied in the larger subty pe of individuals with the high-frequency loss. Gorlin's classificatio n still remains the best system to classify NS-SNHL, and can provide a broad base to separate a very heterogeneous group of disorders. Resul ts obtained in gene mapping in single large human families or in homol ogous gene search could be tested in our families. For some of them. n amely those with high frequency progressive and low-frequency NS-SNHL, testing should already be feasible.