The learning curve in post-operative hearing results in vestibular schwannoma surgery.

PURPOSE

We chronologically investigated whether the hearing preservation (HP) rate improved or not in vestibular schwannoma (VS) surgery.

SUBJECTS AND METHODS

HP surgery has been attempted in 127 VS patients with pre-operative class A and B hearing from 1976 to 1999. The HP rate was chronologically compared with hearing level and tumor size.

RESULTS

The preservation rate of pre-operative class A hearing which was preserved post-operatively as class A has recently been increasing especially in patients with an intracanalicular (IC) tumor. This rate was improved to 67% from 1995, although this was 33% from 1989 to 1994. However, the preservation rate of pre-operative class B in patients with an IC tumor and that of pre-operative class A hearing which was preserved as class A in patients with a larger tumor extending into the posterior fossa, have not improved over the last 10 years.

CONCLUSION

These results indicate that the improvement of the HP rate is mainly due to the increased number of patients with an IC tumor with class A pre-operative hearing. In patients with a tumor of 4-20 mm in size, especially in those showing pre-operative class B hearing, there may be histologically some limitations such as gliosis in the cochlear nerve in the preservation rate of good quality (class A or B) of hearing.