Role of transient-evoked otoacoustic emissions for hearing preservation in acoustic neuroma surgery.

OBJECTIVE

This study aimed to assess whether transient-evoked otoacoustic emissions (TEOAEs), which are known to be expressions of an intact cochlear function, could be useful for the rationale of hearing preservation in acoustic neuroma (AN) surgery.

STUDY DESIGN

The TEOAEs were measured before, during, and after surgery in a consecutive series of patients affected by cerebellopontine angle tumors.

SETTING

The study was performed at the Department of Otolaryngology, University "La Sapienza" of Rome.

PATIENTS

Five patients with AN and one with a meningioma totally involving the Cochlear (VIII) nerve.

INTERVENTION

Retrosigmoid approach on the ground of the limited AN size (within 20 mm) and the 30/70 rule, as proposed by the American Academy of Otolaryngology-Head and Neck Surgery nomogram. Two patients also were selected despite a poor hearing level and the absence of TEOAEs.

MAIN OUTCOME MEASURES

Preoperative and postoperative pure tone audiometry compared with TEOAEs. Intraoperative TEOAEs were compared with electrocochleographic findings.

RESULTS

The TEOAEs were found to be present also in patients with AN with poor pure-tone average (PTA) threshold (i.e., > 75 dB). Intraoperatively, TEOAEs recording showed to be markedly affected by the environmental noise as well as by specific intraoperative maneuvers, such as drilling of the internal auditory canal or tumor removal or both. In the three patients in whom hearing successfully was preserved. TEOAEs were present in the first postoperative days, despite a temporary deterioration of the PTA threshold.

CONCLUSIONS

The intraoperative use of TEOAEs showed to be scarcely reliable, whereas their presence in the preoperative assessment of patients with AN could lead to an extended number of patients to be selected for hearing-preservation surgery. Finally, an early postoperative identification of TEOAEs may be considered a favorable prognostic sign for foreseeing a delayed pure-tone hearing threshold recovery.