Effects of glycerol on cochlear frequency selectivity in patients with Menière's disease.

During transtympanic electrocochleography, action potential (AP) tuning curves were derived as a measure of cochlear frequency selectivity. In 18 out of 21 patients with symptoms of Menière's disease, a poor frequency selectivity was observed. In 12 subjects the effects on frequency selectivity of oral glycerol were measured, and in 5 patients AP tuning curves indicated an improvement in sharpness of tuning by a factor of 1.5-2.5. These changes started approximately 30 min after oral glycerol administration. In 2 subjects there was a deterioration in AP tuning. In 5 patients no significant changes were observed.