oVEMP to High Frequencies Show Semicircular Canal Dehiscence.

Objective: In 26 patients with CT-verified SSCD, to investigate the effect of frequency on the n10 component of the ocular vestibular-evoked myogenic potential (oVEMP n10) evoked by air conducted sound (ACS) and bone conducted vibration (BCV) at the midline forehead at the hairline (Fz). Methods: A handheld Bruel and Kjaer 4810 minishaker provided BCV stimulation was used, using surface EMG electrodes beneath both eyes to record oVEMP n10. The stimulus ACS and BCV at either Fz or at the vertex of the skull (Cz) were tone bursts ranging from 125 Hz to 8000 Hz. Twenty-seven healthy subjects were tested in the same paradigm. Results: In response to ACS and Fz BCV from 125 Hz until 8000 Hz in SSCD patients the oVEMP n10 amplitude beneath the contraSSCD eye was substantially and significantly larger than the oVEMP n10 beneath the ipsiSSCD eye. In normal patients, ACS oVEMPs n10 is present and reproducible until 1000 Hz, while in SSCD ACS oVEMPs n10 is present up to far higher frequencies (8000 Hz). To Fz BCV oVEMPs n10 is present until 8000 Hz in 23 patients but only to 1000 Hz in normal patients. Conclusion: Testing OVEMP frequency tuning with ACS and BCV allows very simple, very fast identification of a probable unilateral SSCD in a manner which is very easy even for senior patients.