Contralateral suppression of transient evoked otoacoustic emissions: intra-individual variability in tinnitus and normal subjects.

Contralateral acoustic stimulation reduces the amplitude of the transient evoked otoacoustic emission (TEOAE) in humans. The mechanism is thought to be mediated, at least in part, through the medial olivocochlear efferent system innervating the outer hair cells. To assess its usefulness as a possible clinical test, TEOAE suppression was measured in each ear of 12 subjects over a 6-week period, and these data are shown in detail for four subjects representing extremes of variability in a tinnitus and a non-tinnitus group. Intra-subject test results (n = 18) exhibited a varying extent of suppression values and the variance of each session, consisting of three tests, was not statistically different from one session to another. There was no dependence on variables such as ear (right or left), session, day of testing or their interaction. There was a significant difference in the variability between the tinnitus and the normal group.