[Objective methods for simulated detection of unilateral deafness with special reference to DPOAE (distortion-product otoacoustic emissions) exemplified by a case report].

The simulation of unilateral deafness is very rare. Objective findings are of special interest if it happens. A patient with alleged deafness on the left-hand side due to commotio cerebri was treated in our hospital. Pure tone audiometry showed deafness on the left-hand side and normal hearing on the right-hand side. However, stapedius reflexes were found ipsilaterally left as well as contralaterally right, at 0.5 to 2 kHz with a stimulation of approximately 90 dB SPL. Transiently evoked otoacoustic emissions (TEOAE) and distortion-product otoacoustic emissions (DPOAE) were measured. The TEOAE had the same reproducibility but a very low response on both sides, such that inner ear function could not be evaluated. In comparison, the DP gram showed clear DP amplitudes over the whole frequency range on both sides. Nonphysiological DPs could be excluded by assessing the DP growth rate at three different frequencies. By means of brainstem electric response audiometry (BERA), with which the IV/V complex was detectable up to stimulation with 20 dB SPL clicks, and the Stenger test, a neural or central hearing loss could be excluded. Normal hearing on the left-hand side was thus confirmed. In cases of simulated deafness it is possible to prove a normal inner ear function by DPOAE. DPOAE therefore complements the list of potential audiological simulation tests.