Unraveling Cochlear Dynamics: The Effect of Clicks, Tone Burst Frequencies, Polarity, and Stimulus Rates on Cochlear Microphonics in Individuals with Normal Hearing

BACKGROUND: Despite cochlear microphonic's potential clinical application, especially in ANSD diagnosis, the optimal parameters to record cochlear microphonics and the effect of various stimulus parameters are not well understood yet, which makes its recording a difficult procedure. The present study was undertaken to determine the effect of stimulus polarity, rate, stimulus type, and stimulus frequency on different aspects of cochlear microphonics, which could help to decide an optimal stimulus parameter that can be used to record CM. METHODS: The study involved 32 normal-hearing adults. CM was recorded from these individuals using extratympanic CM measurement from the ear canal independently for tone burst frequencies (500 Hz, 1 kHz, 4 kHz & 8 kHz) and click stimuli having rarefaction and condensation polarity at 30.1/sec and 59.1/sec repetition rates. Amplitude and latency were measured from the recorded waveforms and compared across and between stimulus conditions. RESULTS: Results reveal that stimulus frequency and stimulus type have a significant effect on different parameters of CM. However, there was no significant effect of stimulus polarity and rate of stimulus on the amplitude and latency of cochlear microphonics. The amplitude and latency of the cochlear microphonics are inversely proportional to the stimulus frequency. CONCLUSION: Hence, the study suggests the use of low-frequency tone burst (500 Hz/1 kHz) to elicit robust CM, which has greater application in the assessment of cochlear functioning over OAE as the latter gets affected by environmental and physiological noise and also due to middle ear pathology.