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Background and ObjectivesZZSudden deafness, an important disease characterized by abrupt sensorineural hearing loss, is rare in children and the prognosis in children is accepted to be worse than that in adults. However, clinical studies are not sufficient to define the clinical characteristics and prognosis of sudden deafness in children. The author analyzed clinical manifestation of sudden deafness in children and compared the treatment results of children with those of adults.Subjects and MethodZZA retrospective analysis was performed in 25 patients (29 ears) who were treated for sudden deafness from January 1993 to May 2008.ResultsZZ1) The overall hearing recovery rate (79%) was significantly higher in adults (53.7%). The prognosis in children less than 10 years old (73%) was also higher than that in adults. 2) The rate of complete recovery (61%) was higher in children than in adults (38.5%).ConclusionZZThe sudden deafness in children has unique clinical characteristics and the recovery rate is more favorable than in adults.

Cholesterol granuloma is a histological term used for the description of a tissue response to a foreign body such as cholesterol crystals. The pathogenesis of cholesterol granuloma is controversial. But three factors are thought to have an important role in its development: obstruction of ventilation, impaired drainage, and hemorrhage. It may arise from any portion of the pneumatized temporal bone. But huge cholesterol granuloma with intracranial and extradural extension has been rarely reported. Recently, we experienced a case of huge cholesterol granuloma with intracranial and extradural extension. The patient has never experienced chronic otitis media before. The cholesterol granuloma was successfully removed by transmastoid approach. So we report this case along with a literature review.

The performance and safety of a retainer-type ball valve have been evaluated for use in a high-pressure pipeline to a district heating plant. The retainer-type ball valve is a developed valve improving the defects of the leaks that may occur in the general valves such as the floating ball valve or trunnion ball valve. To verify the valve design, a numerical analysis of the design has been applied to investigate safety factors and to determine the flow coefficients for the DN300 and DN400 standard sizes. The conditions used for the numerical analysis was based on the international standards ISO 5208, IEC 60534-2-3, and a high-pressure pipeline to a district heating plant. The structural analysis results comprise deformations, equivalent stresses, and safety factors, and the flow analysis results show the flow coefficient, the pressure distribution, the velocity vectors, and the flow patterns for each rotation angle. These results confirmed the characteristics and reliability of the retainer-type ball valve and, based on these studies, we proposed a retainer-type ball valve as a solution to solve the leakage problem.