TRANSIENT AND DISTORTION-PRODUCT OTOACOUS TIC EMISSIONS IN THE DIAGNOSIS OF PROFOUND HEARING-LOSS

Transient click-evoked otoacoustic emissions (TEOAE) and distortion-pr oduct otoacoustic emissions (DPOAE) are produced by an active biomecha nical process in the cochlea, presumably related to outer hair-cell ac tivity. Although it is generally accepted that in most cases of hearin g loss with absent auditory evoked potentials neither TEOAE nor DPOAE can be found, some cases with such a constellation have been described . Here we report another four cases of children with severe to profoun d hearing loss where we discovered reproducible TEOAE and DPAOE, where as auditory evoked potentials were missing. TEOAE and DPOAE recordings in these cases indicate substantially preserved outer hair-cell funct ion independent of profound pre-sensineural hearing loss. Since the in cidence of children with preserved otoacoustic emissions together with impairment of synaptic or postsynaptic function of the first neuron i s not known,the unconditioned use of TEOAE nor DPOAE as a screening in strument must be seriously questioned. Secondly, in conjunction with s ubjective audiometry and brain-stem-evoked potentials, emission record ings is an indispensable measurement prior to cochlear implantation an d use of high-power hearing aids.