Intraoperative Electrocochleography: A Window Into Endolymphatic Hydrops in a Patient With an Endolymphatic Sac Tumor

Objectives: Intraoperative electrocochleography (ECochG) provides valuable information regarding inner ear function during surgical procedures. Here, we report findings from ECochG collected at three time intervals during the management of a patient with symptoms of inner ear hydrops. Patients: A 38-year-old man with an endolymphatic sac tumor who demonstrated classic meniere's symptoms. Interventions: Endolymphatic shunt, tumor biopsy, and definitive resection of an endolymphatic sac tumor. Main Outcome Measures: Intraoperative ECochG measurements at three time intervals, using frequency-specific tone bursts and clicks. Results: Across time intervals, the amplitude of ECochG summation potential (SP) responses decreased for tone bursts of all frequencies. On the other hand, the SP response to the click stimulus, and the ratio of the SP to action potential (AP), basically remained unchanged across time points. Conclusions: Results suggest that the absolute amplitude of the SP response to frequency-specific tone bursts may be more sensitive to inner ear hydrops than the traditionally used SP/AP ratio as a response to click stimuli.