Clinical significance of the summating potential in Menière's disease

Transtympanic (TT) electrocochleography (ECochG) data recorded with click stimuli and tone bursts (1, 2, 4, and 8 kHz) were evaluated in 50 patients with Meniere's disease and compared with the data from control groups of 10 sensorineural hearing impaired patients and 5 subjects with normal hearing. The mean summating potential (SP) amplitude was larger in the Meniere's disease group for 1, 2, and 8 kHz. The low frequency (1 or 2 kHz) SP decreased in 59% of the Meniere's disease patients during a glycerol dehydration test, whereas subjective hearing improved in only 29%. The use of ECochG with the monitoring of SP thus improves the sensitivity of the glycerol test for the detection of endolymphatic hydrops. There appeared no clear relation between clinical observations and the ECochG data either before or after glycerol. However, the Meniere's disease patients with a large negative SP at low frequencies also had larger action potential (AP) and often had short-term symptoms. The present report confirms the usefulness of measuring the SP in the diagnosis of Meniere's disease.