Estudo da etiologia da surdez neurossensorial em recem-nascidos de alto risco / Etiological study of the sensorioneural deafness in high risk newborns

AUTOR(ES)
DATA DE PUBLICAÇÃO

2008

RESUMO

The frequency of sensorioneural hearing loss in high-risk newborns is 20-40 in 1000 births. In many cases, the cause is environmental, due to prenatal, perinatal and postnatal factors, or caused by genetic factors. The main objectives of this project were to determine the etiology of the hearing loss in children admitted into Neonatal Intensive Care Unit (NICU) and compare with other factors, mainly ototoxic medication. 4 different groups were selected: 25 pre-matures (from NICU) with sensorioneural nonsyndromic hearing loss (group A), 25 pre-matures (from NICU) without hearing loss (group B); 25 full term children with sensorioneural nonsyndromic hearing loss (group C) and 25 full term children without hearing loss (group D). The main mutations which cause hearing loss were studied: 35delG (GJB2 gene), A7445G, G7444A (CO1 mitochondrial gene), A1555G, C1494T, A827G, T961G and 961delT/insC (in the 12S rRNA mitochondrial gene and, in general, modulated by aminoglycosides), ?(GJB6-D13S1830) and ?(GJB6-D13S1854) (in the GJB6 gene). The complete GJB2 gene was sequenced in cases where the 35delG mutation wasn´t found, or where it was found in heterozygosis. 1 child was found with V37I in heterozygosis (GJB2 gene) and 2 with the A827G mutation in group A. 3 children were found with the A827G mutation in group B. 5 children were found with the A827G mutation and 5 others with 35delG in homozygosis in group C. In group D only 1 child was found with the mutation A827G. These results show that A827G mutations might be modulated by more than one factor, like aminoglycosides or nuclear modifier genes. The 35delG mutation might be directly related to prelingual profound congenit losses. Comparing groups A and B, Mann- Whitney´s Test showed significant results in the NICU period average (p-value = 0,003), indicating that this diference could be the major cause of hearing loss in group A. The Mood Test showed highly significant hearing loss diference in both ears between groups A and C (left ear p-value = 0,002 and right ear p-value = 0,000), showing severe loss in group A and profound loss in group C, indicating that in group C this loss is probably caused by genetic factors that induce prelingual bilateral profound loss, as related in previous GJB2 studies. In cases of hearing loss where mutations couldn´t be found, it is possible that it has been caused by other mutations not studied or environmental causes. Therefore, the screening of mutations is important because it could provide better chances of developing speech and language

ASSUNTO(S)

recem-nascidos infants (newborn) surdez deafness fatores de risco genetics genetica risks factors

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