Ménière's disease and the summating potential. III. Effect of glycerol administration

We investigated the effect of administering hypertonic glycerol on cochlear and auditory nerve responses to rectangular-pulse clicks and on pure-tone behavioral thresholds. Eleven ears with Ménière's disease, and 20 ears without the disease were studied. Among the ears with Ménière's disease summating potential (SP) amplitudes decreased and 250 to 1,000-Hz thresholds improved after glycerol administration. Action potential amplitudes from the ears with Ménière's disease also decreased after glycerol ingestion, but to a lesser degree. In contrast, among the ears without Ménieère's disease, 250- to 1,000-Hz behavioral thresholds did not change significantly after glycerol nor did any of the electrophysiologic responses. Analogous group differences were found when the ears were regrouped according to the presence of absence of pathologic SP enlargement. These results demonstrate a tendency for three variables-(1) clinical diagnosis of Ménière's disease, (2) enlarged SP, and (3) positive glycerol test result-to cluster together in the same population of ears.