GJB2 (connexin 26) mutations and childhood deafness in Thailand.

HYPOTHESIS: The purpose of this study was to elucidate whether GJB2 mutations are responsible for childhood deafness in Southeast Asia. BACKGROUND: GJB2 mutations are responsible for a large part of childhood deafness in many countries. In Whites, there is a common mutation (35delG) that accounts for about 70 to 80% of the GJB2 mutations. Previously, we and others reported a common GJB2 mutation (235delC) in Japanese patients with prelingual deafness. The association of the 235delC mutation with a single haplotype suggested a founder effect of the mutation. METHODS: We analyzed the GJB2 gene in 17 deaf patients from 12 unrelated families in Thailand. Genomic DNA was extracted from peripheral lymphocytes of each patient and the entire coding region of the GJB2 gene was sequenced. RESULTS: GJB2 mutations were found in 4 patients in 3 families. Patient 1 was a homozygote of 235delC. Patient 2 was a compound heterozygote of 235delC and W24X (71G --> A). Patient 3A and 3B (in 1 family) were heterozygotes of a novel mutation M34L (100A --> T). CONCLUSION: The 235delC mutation may be widely distributed in Asian countries outside of Japan.

Incidence/prevalence of sensorineural hearing impairment in Thailand and Southeast Asia.

The Bangkok Otological Center (ISA-HI-lFOS/World Health Organization Collaborating Center) carried out a series of prevalence studies of hearing impairment throughout Thailand. This report includes background information for Thailand and its medical personnel and the results of five studies in different regions from 1988 to the present. This report emphasises sensorineural hearing loss (SNHL). Study I in three Thai provinces showed SNHL at 18.6 per cent. These results were considered abnormally high due to a number of extraneous reasons. Study 2 was conducted in 17 provinces in 5 regions and in Bangkok. Results showed that 8.3 per cent of those tested had a SNHL. Study 3, The Crown Prince Project, involved 21 Crown Prince Hospitals and showed an overall SNHL of 4.6 per cent. Study 4 was the Thai-Swedish project, where SNHL was reported at 22.7 per cent. Study 5 involved school children aged 6 to 15 in both rural Thailand and Bangkok. Results showed SNHL in Bangkok children at 3.5 per cent compared to 3.6 per cent in the rural children. After a careful review of the various studies, the overall results have been interpreted to suggest that the prevalence of SNHL in Thailand is between 3.5 and 5 per cent.

Audiological development in South-East Asia. Thailand health profile.

The Otological Centre:Bangkok Unit has been established since March 13, 1985 on the initiation of ISA and IFOS as one of the planned three Centres for each continent of the world. Bangkok Centre serves the Asian countries on the Global Programme on Prevention of Hearing Impairment and Deafness. It was the first of the planned three centres to be established and operative. The Centre has already run Annual Training Courses to upgrade oto-audiological knowledge of ENT doctors and personnel engaged in this field. Three courses were run with a very successful result. The epidemiological survey and services of ear diseases and hearing problems were carried out in various parts of Thailand rural areas as well as in the Bangkok metropolitan area in cooperation with the Provincial Health Offices and Provincial and District Hospitals and Bangkok Metropolitan Health Centres. Emphasis was placed on the early detection, management and preventive measures to the early diseases and hearing disorders. The Centre's mobile team is run on a voluntary basis without any financial support. The problem cases found were treated and referred to the appropriate health units, health centres or hospitals according to convenience and suitability. Some difficult cases in need of further investigation were recommended to seek specialist attention at the closest hearing centre. Essential for services at the spot is hearing aids provision free of charge or as cheap as possible, since more than 50% of congenital hearing impaired children have never before used hearing aids as this is either not affordable or not available in rural areas. Financial support is crucial for further development and running of the Centre. International help will also be needed for training of personnel both at the site of the Centre and overseas. An acoustic laboratory is essential for the future development of the Centre. The Ear Foundation (Thailand) was set up in January 1987. Some personal as well as international support in all aspects is essential for the further development as well as to cope with the maintenance costs of the Bangkok Centre. Our hope is that "Hearing for All by the Year 2000" will be true for all sectors.

Tympanic membrane perforation descriptors and hearing levels in otitis media.

The air conduction threshold of hearing was determined at 0.5,1 and 2 kHz by manual audiometry on a consecutive series of young Thai adults with bilateral chronic suppurative otitis media. At the same time, after visual inspection of each tympanic membrane, the perforation was drawn, as faithfully as possible in respect of both shape and relative size, on a 40-mm diagram of a tympanic membrane. A study of the shapes of perforations showed that they could be described as elliptical, reniform or cardioid. For the purposes of calculating the area of a perforation, a reniform perforation was considered to be the result of substracting a smaller ellipse from a larger ellipse, which ellipses were in contact at the point of least curvature. The hearing threshold level was found to be a function of the size of the perforation. A power function best described this relationship. The relationship was such that a total perforation would be associated with a hearing loss of about 60 dB HL over the frequency range 0.5-2 kHz.

Gnathostomiasis. A case of otological interest.

A young Thai man was afflicted with neurognathostomiasis. The symptomatology was distinct from that of eosinophillic myeloencephalitis. In view of its neurootological flavor, it is proposed that this newly described symptomatology of neurognathostomiasis should be referred to as the neurootological gnathostomiatic syndrome(NOGS).