Increased amplitudes of distortion product otoacoustic emissions in patients with unilateral acoustic neuroma.

We present a case series of 4 patients with a unilateral acoustic neuroma and increased amplitudes of the distortion products of otoacoustic emissions (DPOAEs) at the low- and middle- frequency bandwidth on the involved side compared to the uninvolved side despite a 28-dB hearing level (HL) worse (compared to the uninvolved side) pure-tone hearing threshold average for standard audiometric frequencies between 1 and 6 kHz at the involved side. In 3 of these patients, 2 with an inferior vestibular nerve origin of the acoustic neuroma and one in whom the nerve of origin could not be unequivocally defined, the tumor was extending extrameatally. One patient had a purely intrameatal acoustic neuroma of superior vestibular nerve origin. Moreover, notable was the presence of the DPOAEs in all of the involved ears despite elevated pure-tone hearing thresholds (pure- tone averages for the standard audiometric frequencies between 1 and 6 kHz ranging between 36 and 62 dB HL).