Electrocochleography in Meniere's disease: recovery from adaptation of the auditory action potential

Abstract

Conclusions: High prevalence rate of an enhanced summating potential (SP)/action potential (AP) ratio (≥0.35) is considered to result largely from the imbalances of Ca2+ homeostasis in the endolymphatic space. An increase in Ca2+ is thought to augment the SP. Furthermore, a greater inflow of Ca2+ into inner hair cells is supposed to influence the disturbed release of neurotransmitter, which may induce pathological functioning of inner hair cell synapses. We speculate that such abnormal synaptic functioning is responsible for the development of abnormally increased AP recovery from adaptation (iR). Objectives: This study aimed to record the AP recovery from adaptation (AP recovery) and to investigate its clinical significance in association with other electrocochleography (ECochG) findings in Meniere's disease. Methods: ECochG was performed transtympanically in 27 patients with Meniere's disease. AP recovery was measured by a paired-click stimulation paradigm as a function of interclick intervals from 5 to 100 ms. Results: High prevalence of SP/AP ratio was observed in 27 patients. iR, suggesting abnormal functioning of inner hair cell synapse, was in many cases combined with an enhanced SP/AP ratio.