Delayed Response Following Cochlear Microphonics; Its Clinical Significance.

Transtympanic electrocochleography (ECoG) with 1000Hz tone-bursts and clicks was performed in 262 patients (262 ears) who visited the JA Yamaguchi Shuto General Hospital.The cochlear microphonics (CM), action potentials (AP) and summation potentials (SP) were analyzed.1) There were some patients with a delayed response following the tone-burst evoked CM, but others did not show such a delayed response.2) Delayed responses following a tone-burst evoked CM were frequently evoked in patients with a normal hearing level and in patients with high frequency sensorineural hearing loss.3) Patients with a delayed response following a tone-burst evoked CM appeared to have a better overall hearing level, lower click-evoked AP detection thresholds and a larger click-evoked AP amplitude than those without a delayed response.4) The tone-burst evoked CM detection thresholds were correlated with pure tone thresholds at a frequency of 1000Hz, and with the average pure tone hearing level within a frequency range of 500-4000Hz.