Study of Long-Term Results of Fenestration

Abstract

1. The present research deals with 109 cases of fenestration for otosclerosis which have been followed up from the functional point of view for 8 years.

2. The percentage of success based upon the attainment of social hearing (threshold below 35 db) shows a slow progressive decrease (from 86% to 63% for A cases, and from 68% to 49% for B cases). See Fig. 1.

3. The same holds true for percentages obtained from an evaluation of the absolute hearing gain (gain in db as compared with the preoperative threshold). On the basis of these findings, the prognosis of intervention becomes more favourable for B cases compared with A cases, as the percentage of satisfactory hearing gains is logically higher for group B (Fig. 2).

4. In 73% of cases the hearing gain obtained through intervention was higher than 10 db 8 years later.

5. A comparison between the mean curve of the primary hearing gain and the curve after 8 years shows that the threshold for low and middle frequencies (up to 2000) is very slightly increased, whereas there is a more considerable fall for high frequencies (above 2000 Hz), (Fig. 3).

6. A comparison with the unoperated ear shows that the mean hearing curves behave in the same way (Fig. 4).

7. The study of success rates in patients on the basis of groups of primary hearing loss (audiometric air curve) has shown that they are very similar in the first two groups (1st group with a hearing loss up to 45db; 2nd group with hearing loss between 46 and 55db). Prognosis should be based more on the evolution stage of the otosclerotic process than on the hearing level at the time of operation (Fig. 5).

8. Another important factor in prognosis during the initial stages of the disease is age at the onset of otosclerosis. The highest success rates were obtained in patients aged over 30; the percentage of favourable results is lower for patients under 30 and shows a further decrease in the long run (Table VIII). In a more advanced stage of the disease, the results are only apparently better in young subjects, as in the course of time they are considerably worse. The success rate for subjects over 30 is lower, but it is maintained in a majority of cases.

9. All these data show the extreme importance of the evolution stage of the disease at the time of intervention on the further evolution of the functional results.