The author conducted hearing tests on 39 patients who had had the operation of radical mastoidectomy for the purpose of improvement of power of hearing, and the results were as follows:
1) 20.5% of the patients showed improvement of hearing by more than 15 dbs. in the speech range,(hereinafter referred to as the improved group), and 46.2% were those who made improvement or exacerbation of less than 10 dbs.,(hereinafter referred to as the unchanged group), while the rest of 33.3% showed exacerbation of hearing by more than 15 dbs.,(hereinafter referred to as the exacerbated group).
2) With each group, about 50% had had medium grade disturbances of the middle ear. While in the improved group the percentage of high grade disturbances was equal to that of low grade disturbances, low grade disturbances were a little less than the other in the unchanged group, and in the last group high grade disturbances were twice as many as the cases of low grade disturbances.
3) The cases in which the skinflap adhered to the tympanic cavity amounted to 25% in the improved group, 66% in the unchanged, and 84% in the exacerbated.
4) Out of patients who had had better hearing by air conduction than 40 dbs. before operation, 2 cases belonged to the improved group, 3 to the unchanged, and 9 to the exacerbated. From the cases in which the power of hearing had been between 40 and 60 dbs., 3 belonged to the improved group, 9 to the unchanged group and 3 to the exacerbated group. On the other hand, 3 out of the patients whose power of hearing had been lower than 60 dbs. belonged to the improved group, 6 to the unchanged group and 1 to the exacerbated group.
5) In many of the cases in which the power of hearing lowered than before after the operation, the disturbances of bone conduction had existed and D. L.-tests had been positive.
