A review is made on 426 sensori-neural hearing impaired children who visited the department of Oto-Rhino-Laryngology of Sapporo Medical School from April, 1, 1977 to May, 31, 1986. The following results were obtained.
1) We found no difference in incidence between males and females. (males: females=217: 209)
2) The number of bilateral hearing impaired children were 191, and unilateral impaired children were 235. (right side: left side=120: 115)
3) The peak of first visiting age was 6 years old.
4) We found that almost cases with bilateral sensori-neural hearing loss (severe type) were detected by 7 years old, with the peak at age three.
5) The number of unilateral hearing impaired cases that were found before age three was very few.
6) In bilateral severe hearing impaired children, 34% of cases were presumed as of hereditary, fetal, and perinatal origin. And the 4% of cases were presumed as acquired hearing impairement. The etiology of other cases was unknown.
7) It was more difficult to presume the causes of unilateral deafness than those of bilateral severe hearing impaired cases because unilateral hearing impaired children had less complaints than severe bilateral hearing impaired children did. We were able to presume the etiology in 25% cases of unilaterally deaf children. Mumpus was the principal cause that occupied 62.5% of aquired origins.