Electrocochleographic signal analysis: condensation and rarefaction click stimulation contributes to diagnosis in Menière's disorder.
Thirty patients with Menière's disorder, 11 patients with cochlear hearing loss of other aetiologies and 10 normally-hearing subjects, were investigated using transtympanic electrocochleography (TT ECochG). Alternating polarity clicks, condensation and rarefaction clicks and long tone-bursts of 1 kHz were used for stimulation. The latencies of the AP responses to click stimulation were evaluated. It was found that the latency differences between the condensation and rarefaction click-evoked responses were significantly larger in patients with Menière's disorder as compared to normal subjects and to patients with other cochlear hearing losses. It was found that the sensitivity of TT ECochG, obtained by using measurements of SP-AP ratios and the SP amplitude at 1 kHz burst stimulation, increased from 83 per cent to 87 per cent by addition of the con-rar shift measurement. The specificity of TT ECochG obtained by this combination of variables was 100 per cent in our material. The results of the study indicate that the latency shift found in responses evoked by clicks of opposite polarities in TT ECochG, can be a useful parameter in the detection of suspected endolymphatic hydrops.