Review article

CLINICAL AND GENETIC SCREENING OF CONGENITAL DEAFNESS

Sanja Zaputović orcid.org/0000-0001-9415-9618 ; Department of Gynaecology and Obstetrics, Clinical Hospital Center, Rijeka, Croatia

Abstract

The incidence of congenital hearing impairment is at least 1/1000 newborns. Approximately one half of hearing impairments is hereditary, out of which one third occurs as part of different syndromes (syndromic deafness), and in two thirds of these cases deafness is the only symptom (non-syndromic deafness). It is considered that around 200 ­different genes cause various forms of hereditary deafness. The development of molecular genetics has enabled significant progress in the detection and localization of these genes. Mutations of the gene that encodes the connexin-26 synthesis cause more than half of all hereditary deafness cases. In 1994, Guilford first described autosomal recessive non-syndromic deafness in locus DFNB1 13q11-q12 on the 13th chromosome. In the inner ear, connexin-26 plays a role in the recycling of potassium ions from hairy cells base, through supporting cells and fibroblasts to stria vascularis, from where they are then discharged into endolymph via special channels. On its way, potassium ions pass through gap junctions composed of connexin-26, connexin-30 and connexin-31. Mutation in any of the genes that encode connexins alters the ionic composition of sensory cells and results in the development of deafness. Newborn hearing impairment screening started developing some 40 years ago. Audiologic screening by evoked otoacoustic emission method (E-OAE) aims at detecting as many children as possible with hearing impairment. Children who after using this method are suspected of having hearing impairment are then referred for automated auditory brainstem response. In children with positive audiologic findings, molecular-genetic testing is today possible for a large number of genes, however, due to the significant prevalence of mutations in the connexin genes, only such a testing is more widely accepted. Combination of audiologic and molecular-genetic analysis has proven to be complementary, useful and applicable in practice.

Keywords

newborn; deafness; otoacoustic emission; genes; mutation; neonatal screening

Hrčak ID:

23414

URI

https://hrcak.srce.hr/23414

Publication date:

1.6.2007.

Article data in other languages: croatian

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