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.