Preservation of hearing in the surgical removal of cerebellopontine angle tumors.

It is claimed that postsurgical hearing preservation is possible in about 5 to 8 per cent of cases of acoustic neuroma. Even with small tumors, hearing preservation can be accomplished in about half of the patients who are fortunate to have anatomic integrity of facial and cochlear nerves, as well as intact inner ear blood supply at the end of the surgical procedure. Monitoring of seventh and eighth nerve function through evoked potentials may be important. On the other hand, even if evoked potentials are preserved during surgery with wave V latency and amplitude similar to preoperative recording, hearing may still be completely lost during the immediate postoperative period. There is no predictable pattern that assures postoperative preservation of hearing. In Case 2, the seventh and eighth nerves as well as the inner ear blood supply were carefully dissected and anatomically and electrophysiologically preserved during the intraoperative period. At the end of the surgical procedure, the evoked potentials were the same as preoperatively. Nevertheless, the patient ended up with no detectable hearing postoperatively. We feel that the suboccipital-retrosigmoid transcanal approach can be safely used for the removal of cerebellopontine angle tumors of all sizes. We believe the argument that "only the translabyrinthine approach can accomplish total tumor removal" is not valid. No complications have been attributed by having the patient in the semisitting position. Older patients, who cannot tolerate the semisitting position, are operated on while in the park bench position. Planned subtotal removal of a CPA tumor is done with the patient in the supine position (transmastoid-retrolabyrinthine or retrosigmoid). The relationship between the otologic surgeon and neurosurgeon is very important. The surgical approach used should be selected on the basis of the combined experience of the surgical team. Finally, an attempt should be made to preserve facial nerve function and hearing in all suitable patients. The postoperative course using the suboccipital-retrosigmoid approach is usually benign, and the patients are discharged from the hospital between 7 and 10 days following surgery. The translabyrinthine approach, in our opinion, should be reserved for smaller lesions in patients with anacusis or with residual hearing that is not worth saving.