Electrocochleographic Changes Predict an Early Sign of Cochlear Degeneration

The purpose of this study is to identify the earliest appearing auditory electrophysiological indicators that change with age progression in young adults with normal hearing, and to analyze the frequency distribution patterns of these markers in the cochlear.

In this study, 74 participants with normal hearing were divided into four groups: aged 18-25, 26-30, 31-34, and 35-40 years for statistical purposes. Electrocochleography (EcochG), transient evoked otoacoustic emissions (TEOAE), and Hearing in Noise Test (HINT) were used.

Our study found: (1) EcochG action potential (AP) and summating potential (SP) amplitude of the left ear decreased after 25 years except at 6 kHz. (2) The strength of EcochG AP amplitude peaks at 4 kHz. (3) The EcochG SP/AP has no statistically significant difference between different age groups, and there is no characteristic distribution of frequencies. (4) TEOAE amplitude, TEOAE contralateral acoustic stimulation (CS) amplitude has no statistically significant difference between different age groups. The strength of TEOAE amplitude peaks at 1-2 kHz. (5) There are no significant differences in the HINT among the various age groups. (6) The auditory function of the right ear declines more slowly than that of the left ear.

The study's findings reveal several key insights: (1) The EcochG AP amplitude is the most sensitive electrophysiological indicator of cochlear degeneration. (2) Cochlear electrophysiologic testing exhibits distinct frequency distribution characteristics. (3) There is an inconsistent rate of electrophysiological change between the two ears.