An Etiological Study On Hearing Loss Of 209 Deaf Students In Jilin Province And Mutation Analysis Of GJB2 Gene In The Congenital Deafness Cases

Objective:Hearing loss is most common sensory disorder in the human population.Hearing loss can have a major impact on the life of a child and his family.Because language and communication develop so rapidly during the first 3 yearsof life, an undetected hearing loss is likely to interfere with a child speech,language and communication with others. Hearing loss also can result in learningproblems that affect a child performance at school and bring a serial ofpsychological and society problem .The proportion of hearing impairment attributed to heredity haw steadilyincreased, as environment and infections etiologies have been effectivelycontrolled. For prelingual hearing loss, epidemiological data showed that1neonate in 1000 is born with severe to profound hearing impairment, and half ofthem are attributable to genetic causes. Approximately 70% of this half occurwithout other abnormalities and is thus termed nonsyndromic hearing impairment(NSHI).The other half, with additional anomalies, is termed syndromic. In somecase, postlingual hearing loss is monogenic. For age-related hearing impairment(prebycusis), genetic factors are prominent. So, hearing loss preventions now arefocus of all world.Twenty years ago,infections disease was major cause of acquired deafnessand virus infectiong was major cause of congenital deafness,which had beencontrolled with the medical development and healthy consciousness raising.Ingeneral, sensorineural hearing loss tends to be permanent, and just prevent,nowwe investigated the factors of causing deafness and hearing level on students ofdeaf-mute school in Jilin province In order to study the etiology and the hearingstatus of the deaf students .The incidence of congenital hearing loss is estimated at 1 in 1000 births, ofwhich approximately equal numbers of cases are attributed to environmental andgenetic factors. Autosomal Recessive hereditary hearing loss is the most popular,about 75 %～80 %and the mutation of connexin26 (Cx26) gene (GJB2) is a majorcause of autosomal recessive, which is special in race and regions. In order tocomprehend the ratio of the mutation of connexin26 (Cx26) gene (GJB2) in thecongenital deafness cases of Jilin province, we inspected the mutation ofconnexin26 (Cx26) gene (GJB2) of 41 cases.Method:1,209 students of deaf-mute school in Jilin province, 114 males(54.5%) and 95females(45.5 %) , aged from 4 to 25, are investigated through questionnaire,including age, development, degree, drug, contaction to yawp, pus of ears, tinnitus,giddy, parotitis, measles, scarlatina, intermarriage, et al, And examined withaudiometer。2,41 students of deaf-mute school in Jilin province, 19 males and 22 females,aged from 7 to 19. came down with nervous deafness before the age of 3 ,whoseparents are normal. Standard air-and bone-conduction pure-tone audiometry(250-8000Hz) was administered in all patients using the MADSEN ORBITER 922audiometer, which was calibrated to International Organzation for Standarization(ISO).excluding hearing loss suffering from tympanitis,ear injury and oxtotoicmedicines etc and one case is comparision. The blood samples were obtained todistill the DNA templates .Using polymerase chain reaction (PCR) , the coderegion of Cx26 gene was amplified .Genomic DNAs were extracted by AgaroseGel Electrophores and inspected PCR production coding region.results:1,The defect of the students is generally sensorineural. most of them arenonsyndromic deafness. the degrees of deafness of 209 deaf students could beascertained with 148(70.8 %) students of profound deafness, 49(23.4 %) studentsof severe deafness , 12(5.7 %) students with moderate to severe deafness . Basingon the ability of speech and language, all the students of profound deafness had thedisorder of speech and language, most of them(66.2%)can not speech at all,some(33.8%)can in part. 10.2% students of severe deafness can speech normally,69.4% can in part ,20.4% can not at all. The ability of the students with moderateto severe deafness is increased, most of them(83.3%) can speech in part, some(16.7%)can at all. Causing of 22% congenital deafness cases, genetic factorsranked first etiologically, fallowed by natal factors as the causes of 3.0% of thecases. And causing of 75.5% acquired deafness cases, ototoxic medicine ( such asAminoglycosides ) ranked first etiologically, fallowed by epidemical factors.2,Genomic DNAs from 41 cases were extracted and amplified by PCR for a724 bp coding region by Agarose Gel Electrophores and no abnormal codingregion.conclusion:1,Basing on the investigation of 209 students of deaf-mute school in Jilinprovince genetic factors ranked first causing of congenital deafness casesetiologically, and ototoxic medicine ( such as Aminoglycosides ) ranked firstcausing of acquired deafness cases etiologically.2,As the degrees of deafness raising, the ability of speech and language of thedeaf students is declined gradually. Diagnosis , acousticon and language recoveryin early stage played major roles of socieal communication of the students ofdeaf-mute school.3,The prevalence of deafness causing mutations in connexin26 (Cx26) gene(GJB2) in the congenital deafness cases of Jilin province is lower than that of otherethnic groups.