[Electrocochleographic study of acute low-tone sensorineural deafness]

We assessed 53 patients with acute low-tone sensorineural deafness (LTSD) over the past 10 years using the transtympanic-electrode technique of electrocochleography. The audiometric diagnostic criteria were as follows: Average hearing level at the lower two frequencies (250, 500Hz) greater than 30 dB, and of the higher three frequencies (2, 4, 8kHz) less than 20 dB. Patients were divided into three groups on the basis of their electrocochleographic findings; 33 cases of the endolymphatic hydrops type, 17 cases of the hair cell damage type and 3 cases of the neural damage type. The outcome of these patients was assessed together their electrocochleographic findings. The results obtained were as follows: 1) Most of the improved cases were of the endolymphatic hydrops type and in females in their twenties. All of the improved cases showed high AP and -SP amplitude, but not dominant -SP, and exhibited slight prolonged AP latency. Satisfactory CM responses at 500 Hz were also found. 2) Most of the hair cell damage type exhibited no change, and some unrecovered cases of the endolymphatic hydrops type progressed to Meniere's disease.