Rebound phenomenon in glycerol test.

The glycerol effect for endolymphatic hydrops is well known for an improvement in pure tone threshold three hours after glycerol administration. However, long-term effects of glycerol, i.e., longer than three hours after administration, are unknown. In this study, audiometric tests were administered during 10 hours following glycerol administration in order to determine the long-term effects of glycerol in cases of Meniere's disease, sudden deafness, and normal subjects. The following results were obtained; 1) The long-term effects of glycerol in the pure tone threshold were observed only in cases of Meniere's disease and were classified into the following four types: "descending type", "descending and ascending type", "ascending type" and "unchanged type". 2) The long-term effects, including rebound phenomenon, on hearing ability did not appear in cases of sudden deafness and normal subjects. 3) About 50% of patients with Meniere's disease showed rebound phenomenon on hearing ability and it was considered to be specific for Meniere's disease.