Action potential latency shift by rarefaction and condensation clicks in Menière's disease.

Transtympanic electrocochleography using rarefaction and condensation clicks was performed on 122 ears of 112 patients, including 98 ears of 89 patients with Menière's disease (MD) and 24 ears of 23 patients without Menière's disease (NMD). The mean action potential (AP) latency difference between rarefaction and condensation clicks was 0.40 +/- 0.37 msec in the MD group and 0.06 +/- 0.07 msec in the NMD group (p < .01). An AP latency shift > 0.2 msec was found more often in the MD group (62.2% vs 8.3%) and in ears with an enlarged summating potential and AP ratio (69.7% vs 36.4%). The results suggest that comparison of rarefaction and condensation latencies may serve as a useful addition to electrocochleography in the diagnosis of MD.