Toward Optimizing Cervical Vestibular Evoked Myogenic Potentials (cVEMP): Combining Air-Bone Gap and cVEMP Thresholds to Improve Diagnosis of Superior Canal Dehiscence

Objective: To develop a novel approach combining low-frequency air-bone gap (ABG) and cervical vestibular evoked myogenic potential (cVEMP) thresholds to improve screening for superior canal dehiscence (SCD) syndrome. Study Design: Retrospective study. Setting: Tertiary care center. Patients: One hundred forty patients with SCD and 21 healthy age-matched controls were included. Ears for each patient were divided into three groups based on computed tomography (CT) findings: 1) dehiscent, 2) thin, or 3) unaffected. Main Outcome Measures: cVEMP and audiometric thresholds were analyzed and differences among groups were evaluated. Results: We define the third window indicator (TWI) as the cVEMP thresholds at 500, 750, and 1000 Hz adjusted for the ABG at 250 Hz (i.e., subtracting ABG from cVEMP threshold). The TWI differentiates between dehiscent and nondehiscent control ears with a sensitivity of 82% and specificity of 100%, corresponding to a positive predictive value of 100%. ABGs and cVEMP thresholds were similar for healthy controls and patients with thin bone over the superior canal. Conclusion: This is the largest study to date examining the usefulness of cVEMPs in the diagnosis of SCD. Our “third window indicator” (TWI) combines cVEMP thresholds with the ABG at 250 Hz to improve the ability to screen patients with SCD symptoms Address correspondence and reprint requests to Steven D. Rauch, M.D., 243 Charles Street, Boston, MA 02114. E-mail: Steven_Rauch@meei.harvard.edu D.J.L. and S.D.R. are principal investigators. This study was approved by the Human Studies Committee of the Massachusetts Eye and Ear Infirmary. Protocol numbers: 13-005H and 13-097H. The authors disclose no conflicts of interest. Copyright © 2017 by Otology & Neurotology, Inc. Image copyright © 2010 Wolters Kluwer Health/Anatomical Chart Company

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