ABR AMPLITUDE AND DISPERSION VARIABLES - RELATION TO AUDIOGRAM SHAPE AND CLICK POLARITY

ABR amplitude behaviour to condensation (C) and rarefaction (R) clicks was investigated in normal ears, ears affected by Meniere's disease a nd ears with high-frequency hearing loss (HF ears). The wave IV-V ampl itude-intensity function was steeper in ABRs evoked by R than by C cli cks. This may suggest that two different cochlear generator components , one intensity-dependent as well as one polarity-dependent, contribut e to click-evoked ABRs. Wave IV-V amplitude was significantly higher i n Meniere ears compared to HF ears in spite of comparable 2-4 kHz hear ing loss in the two groups. Hence, audiometric steepness (which is low er in Meniere ears than in HF ears) seems to predict the wave IV-V amp litude decline more precisely than the 2-4 kHz perception threshold. T he wave IV-V dispersion variable (SR IV-V) was close to normal in Meni ere ears, while wave IV-V was more dispersed in HF ears. In general, C click ABRs were less affected than R click ABRs by 'peripheral' facto rs (i.e. intensity and audiometric steepness).