Intraoperative Electrocochleography in Patients with Menière's Disease Undergoing Endolymphatic Sac Decompression and Shunt Surgery

Hypothesis: Objective physiologic changes measured using electrocochleography at the round window (ECOG^RW) are observable during endolymphatic sac decompression and shunt surgery (ELS). Background: Limited effective treatment options are available to patients with Menière's disease (MD) who have failed conservative management, experience persistent vertigo symptoms, and have substantial residual hearing. ELS is a feasible therapeutic option for these patients. However, the efficacy of this procedure has been questioned, and objective measures assessing inner ear physiologic alterations are lacking. Methods: ECOG^RW was measured in patients with MD undergoing ELS. Stimuli consisted of tone bursts (250, 500, 1000, 2000, 4000 Hz) and 100 μs broadband clicks at various intensities (60-90 dB nHL). Cochlear microphonic (CM), summation potential (SP), compound action potential (AP), SP: AP ratio, and CM harmonic distortions were measured. Results: ECOG^RW was completed in 18 patients. The mean SP magnitude at 500 Hz changed significantly from -7.1 μV before to -5.1 μV after ELS (p < 0.05). However, the mean SP: AP ratio in those tested (n = 13) did not significantly change after ELS. CM harmonic magnitudes remained unchanged from pre- to post-ELS (n = 12) across all frequencies. Conclusion: ECOG^RW allows detection of acute electrophysiological changes in the cochlea. However, our results indicate only small objective changes in the low-frequency SP magnitude (500 Hz) immediately after ELS, but not in other frequencies or measures tested (CM, SP: AP, CM harmonic distortions). These results suggest minimal electrophysiological changes occur in the cochlea as a result of ELS.