[Categorizing hearing disorders based on latency deviations in the BERA (brainstem electric response audiometry)].

The dependence of latencies of EAEPs (Early Auditory Evoked Potentials) on stimulus intensity has been determined from measurements at 15 normal hearing subjects. The results are in good agreement with an exponential function, which has been empirically found and fitted to the data. The deviation from this function in case of hearing disorders can be classified in terms of a "latency deviation diagram". In the simplest case of a pure conductive hearing loss, the effect on latencies is a mere shift of all values to higher levels. The resultant latency deviation lines can be computed and the results introduced in the diagram. This has been done in Figure 5 for several values of hearing loss between 10 dB and 50 dB. These lines permit a detailed specification of hearing impairment, as is demonstrated in Figure 6: In the case of pure conduction loss, the latency deviation follows the appropriate line. Inner ear pathologies involving recruitment lead to latency deviations which are much steeper than these lines and which tend to vanish at higher stimulus levels. Retrocochlear disorders exhibit a nearly level independent latency deviation diagram.