[Latency behavior of early acoustic evoked potentials in inner ear hearing loss]

In 101 patients suffering from sensory hearing loss the latency of the auditory evoked brain stem potentials was investigated. In case of minor and moderate pancochlear deafness latency is found to be within normal range. In severe pancochlear hearing loss above 80 dB latency is significantly delayed. In basocochlear hearing disorders the latency-delay is depending on the extent of the frequency loss and on the degree of pure tone threshold shift. If the patient is suffering from a high frequency hearing loss, normal latency will be found in the higher stimulus levels whereas within low levels latency tends to be delayed depending on the cut-off frequency. A general prolongation of latency across all sound pressure levels will take place in cases with steep forms of high frequency hearing loss. For the purpose of investigating the wave-I-latency we used an earcanal electrode in some patients. It can be shown, that in cochlear hearing disorders the latency of wave V is delayed to the same extent as the latency of wave V. After discussing model studies reference values of wave-V-delay as a function of the degree of high frequency disorders are listed