Effects of GJB2 genotypes on the audiological phenotype: variability is present for all genotypes.

BACKGROUND AND AIM: Recent studies have revealed a genotype-phenotype correlation for mutations in the GJB2 gene. Since ethnic difference may have an effect for the degree of hearing loss due to background genes, we aimed to search for confirmation of previously suggested genotype-phenotype correlation in GJB2 deafness in the Turkish population. METHODS: Pure tone audiograms of 63 unrelated probands with GJB2-associated hearing loss having 15 different mutations were obtained and evaluated for correlation between the degree of hearing loss and genotypes. RESULTS: Three GJB2 genotypes identified in more than one family were homozygous c.35delG (44 probands), homozygous p.E120del (four probands) and c.[35delG]+[IVS1+1G>A] (two probands). No statistical difference for the degree of hearing loss was observed when the genotypes were compared individually or grouped according to their effects on the protein. The most likely explanation for this result is the relatively small size of the studied population. Degree of hearing loss was variable in c.35delG and p.E120del homozygotes. Intra-familial phenotypic variability was present for some genotypes. The detailed audiological data for homozygous p.E120del and c.[35delG]+[328delG] genotypes are reported for the first time in this study. CONCLUSION: Previously reported genotype-phenotype correlations for the GJB2 deafness should be cautiously interpreted during the clinical counseling since variability in the degree of hearing loss is present for all GJB2 genotypes.

Transient evoked otoacoustic emissions and contralateral suppressions in children with auditory listening problems.

OBJECTIVES: Transient evoked otoacoustic emissions (TEOAEs) are reflections of cochlear energy produced during the processing of sound. The suppression effect identified as the decrease with the additional tone stimulator of the otoacoustic emission amplitude is use for assessing efferent auditory system function. The aim of this study is to investigate the contralateral suppression effect (CSE) of transient evoked otoacoustic emissions (TEOAEs) in children with auditory listening problems (ALPs) compared to normal hearing children. METHOD: The study group (Group 1) was consisted of 12 ALP children (8 males and 4 females), aged 5-10 years, and associated with receptive and expressive language delay. The control group was consisted of (Group 2) 12 children with normal hearing levels, matched according to gender and age of TEOAEs and CSE of TEOAEs were investigated at 1.0-4.0 kHz in both groups. RESULTS: For right ear, at 1.0 and 3.0 kHz, TEOAE amplitudes of the ALP group were significantly lower than the control group. At 2.0, 4.0 and 5.0 kHz of the right ear and at 1.0-5.0 kHz of the left ear, TEOAE amplitudes were found as not different between ALP and control groups. Suppression values of the ALP group were significantly lower than the control group at 1.0-2.0 kHz of the right ear and at 2.0 kHz of the left ear. At the other frequencies, there was no significant difference between the suppression values of the ALP and control groups. CONCLUSION: Lower suppression values in ALP group at all frequencies (significant at 1.0-2.0 and 2.0 kHz in the right and left ears, respectively) showed that cochlear and cranial maturation of the ALP group may lower than the control group. Since the age profile in both group is similar, we thought that age's effect on this results is not important. Our results showed that children with ALP have auditory processing difficulties in noisy environment. For understanding the efferent auditory system, patients with auditory processing disorders may be evaluated by the help of background noise.