Electrocochleography and the glycerol dehydration test: a case study.

The electrocochleographic changes which occurred during glycerol dehydration in an ear affected by endolymphatic hydrops due to Menière's disease are discussed. This single case study is reported because the recordings were large and stable, and because they clearly showed the electrocochleographic abnormality associated with endolymphatic hydrops; namely, a large summating potential (SP) in relation to the action potential (AP). After dehydration a dramatic improvement occurred in both the pure tone and speech audiogram. The electrocochleogram showed a decrease in the SP amplitude and little change in the AP amplitude so that the SP/AP waveform became almost normal. The significance of these findings is discussed.