Transient evoked otoacoustic emissions pattern as a prognostic indicator for hearing preservation in acoustic neuroma surgery.

OBJECTIVE

To determine whether pre-operative transient otoacoustic emission (TEOAE) patterns are predictive of successful hearing preservation in acoustic neuroma surgery.

STUDY DESIGN

Retrospective observational study.

SETTING

Tertiary referral medical center.

PATIENTS

A convenience sample was identified in whom pre-operative TEOAE data were available in patients undergoing acoustic neuroma surgery from 1993-2004. Ninety-three patients were identified who met this inclusion criterion.

INTERVENTIONS

Subjects underwent attempted hearing preservation surgery via middle cranial fossa or retrosigmoid approaches. Routine audiometry, ABR, and TEOAE.

MAIN OUTCOME MEASURES

Pre- and post-operative pure tone and speech results were categorized into hearing classes A, B, C, and D as described in the American Academy of Otolaryngology guidelines (1995). Hearing preservation was defined by maintenance of the pre-operative hearing class or downgrade to within one hearing class post-op. Pre-operative TEOAE results were divided into five frequency bands and described as positive in each band if there was a response above the noise floor with >50% reproducibility.

RESULTS

Hearing was preserved in 51 patients (55%). Of these, 11 (22%) had positive TEOAE response in all five frequency bands measured (1, 1.5, 2, 3, 4 kHz), whereas 40 (78%) had TEOAE responses ranging from 0 to 4 frequency bands. 42 patients failed to preserve their hearing. Of these, only three (7%) had positive TEOAE in all five frequency bands, and 39 (93%) had TEOAE responses ranging from 0 to 4 frequency bands (p<0.05). Other variables of prognostic significance to hearing preservation in our series included smaller tumor size, tumor location within the IAC, better pre-operative hearing, and shorter latencies on ABR. Logistic regression was then used to compare the prognostic value of TEOAE against these variables. In our series, ABR latencies and 5 frequency band response on TEOAE showed the highest significant correlation to hearing preservation (p<0.05).

CONCLUSION

A robust pre-operative TEOAE frequency band pattern may be used as a favorable prognostic indicator for potential hearing preservation in acoustic neuroma surgery. The prognostic value may be enhanced when combined with other prognostic factors such as tumor size, tumor location, pre-operative ABR and audiometric results.