鼓室形成術後聴力に関する研究

抄録

Audiograms before and after tympanoplasty have been studied clinically in 63 cases, and the following results were abtained.
1. Of the 63 cases, 21 cases (Group 1) were operated upon during the transitional period from the age of radical operation to that of the tympanoplasty and the other 42 cases (Group 2) had thetypical tympanoplasty. It may be said that in the former group the degree of postoperative impairment of hearing acuity was much less than that of previous radical operation.
2. It was clearly shown that tympanoplasty in Group 2 gave a better effect in terms of hearing acuity in comparison with the methods applied in Group 1.
3. In many cases of the Group 1, pure tone audiograms taken postoperatively showed a prominent peak at 2000cps. Unlike Rossberg's opinion, it may be said that the improvement of hearing in the low frequency range below 1000cps needs suitable stiffness with good vibration of the new tympanic membrane and no adhesions in the tympanic cavity. Also the appearance of the peak at 2000cps is conditioned on good vibration of the tympanum rather than being free from adhesions. In addition, the peak at 2000cps has some what the relationship with the acoustic impedance of the internal ear.
4. Pure tone audiometry and speech audiometry were compared pre- and postoperatively and parallelism of the results of both examinations was seen in 60% of the cases. Unbalance between both examinations observed in the rest of the cases (40%) was probably due to interference of sounds with each other and/or reflections of them in the postoperative cavities at the time of actual perception of speech sound.