Distortion-product otoacoustic emission tests evaluate cochlear function and differentiate cochlear and vestibular schwannoma.

OBJECTIVES

(1) To investigate cochlear function in patients with acoustic neuroma by distortion-product otoacoustic emission tests and (2) to evaluate the utility of this method for identifying the nerve origin of acoustic neuroma.

STUDY

DESIGN

Diagnostic test assessment.

SETTING

Community hospital.

METHODS

The study included 196 patients with unilateral acoustic neuroma who were surgically treated in our hospital between April 2008 and March 2011. In all patients, pure-tone audiometry and distortion-product otoacoustic emission tests were conducted before surgery, and tumor size was measured on magnetic resonance imaging.

RESULTS

Superior vestibular schwannoma (n = 112), inferior vestibular schwannoma (n = 80), and cochlear schwannoma (n = 4) were observed. Positive results of distortion-product otoacoustic emission tests were observed in 11 patients with superior vestibular schwannoma, 14 with inferior vestibular schwannoma, and 3 with cochlear schwannoma. They were predictive of cochlear schwannoma, with 75.0% sensitivity (95% confidence interval [CI], 30.6-95.4) and 87.0% specificity (95% CI, 86.1-87.4). Retrocochlear hearing loss was detected in 5 patients with inferior vestibular schwannoma and 1 with cochlear schwannoma. It was also predictive of cochlear schwannoma. This criterion showed 25.0% sensitivity (95% CI, 4.7-66.1) and 97.4% specificity (95% CI, 97.0-98.3).

CONCLUSION

Percentages of patients with positive results on distortion-product otoacoustic emission tests and those with retrocochlear hearing loss differed by nerve origin. Distortion-product otoacoustic emission tests can be of some assistance in differentiating cochlear and vestibular schwannoma.