Estudo da etiologia da perda auditiva em amostra de individuos brasileiros : diretrizes para protocolo de conduta clínica / Study of the etiology of hearing loss in a sample of brazilian individuals : guidelines for clinical management protocol

AUTOR(ES)
FONTE

IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia

DATA DE PUBLICAÇÃO

16/02/2012

RESUMO

Deafness is considered the most prevalent sensory disorder in humans, caused by a variety of environmental and genetics factors. In Brazil, there are no official data regarding the prevalence and etiology of hearing impairment, but it is known that environmental factors are among the major causes. Although a simultaneous testing approach, including clinical exams, audiological, laboratorial, imaging and genetic expands the etiological diagnosis, overloads the healthcare system due to high costs. Thus, the goal of the present study is to evaluate the effectiveness of imaging and genetics tests and their impact on public health, aiming to increase efficiency and reduce costs of the etiological diagnosis of hearing loss. It was conducted an analysis of 100 patients with sensorineural hearing loss, from Department of Otorhinolaryngology of the State University of Campinas (UNICAMP), submitted to cochlear implantation between 2002 and 2010. A detailed investigation was performed in patients, including imaging and genetics analysis. After specific tests, the number of individuals with unknown cause was reduced from 72 to 42 (42% of reduction). Radiologic abnormalities were identified in 29 of the patients, while molecular alterations were found in 31 individuals, including c.35delG, p.V27I, p.M34T, p.V37I, p.E47X, p.L90P, p.V95M, p.K168R, p.W172X in the GJB2 gene, del(GJB6-D13S1830) in the GJB6 gene and m.1555A>G in the MTRNR1 mitochondrial gene. Genetic and imaging results contributed to the etiological diagnosis of 19% and 20% of the cases, respectively. The etiology remained unknown in 42% of the patients, was due to environmental factors in 25%, genetics in 19% and inner ear malformations or other defects in 14% of the cases. It was concluded that both imaging and genetic analysis were important to identify the etiology of hearing loss, however, molecular tests contributed mainly for diagnosis of patients with congenital deafness, while radiologic exams had greater contribution for diagnosis of cases with progressive or sudden hearing loss. The high prevalence of mutations in the GJB2 gene was confirmed, especially the c.35delG mutation, in cases of sensorineural severe to profound bilateral hearing loss. The molecular research had an important contribution to the etiology of deafness, besides providing genetic counseling and a better prognosis for cochlear implantation, as suggested by previous studies. The TaqMan® OpenArray® Genotyping is a promising technique for molecular diagnostic of hearing loss, because it allows the analisys of many mutations in several patients at once, which implies in a faster diagnosis at a lower cost. The sequential protocol enables an optimization of the etiological diagnosis and cost reduction, as opposed to simultaneously holding imaging, laboratory and genetic tests. Finally, even with a careful investigation, the unknown etiology prevailed as main cause which points to the need of carrying out detailed genetic studies in those cases with idiopathic hearing loss in order to elucidate the diagnosis.

ASSUNTO(S)

surdez - diagnóstico surdez - etiologia protocolos medicos genética implantes cocleares hearing loss hearing loss clinical protocols genetics cochlear implant

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