Ocular vestibular evoked myogenic potentials in superior canal dehiscence

Objective:Patients with superior canal dehiscence (SCD) have large sound-evoked vestibular reflexes with pathologically low threshold. We wished to determine whether a recently discovered measure of the vestibulo-ocular reflex—the ocular vestibular evoked myogenic potential (OVEMP)—produced similar high-amplitude, low-threshold responses in SCD, and could differentiate patients with SCD from normal control patients.Methods:Nine patients with CT-confirmed SCD and 10 normal controls were stimulated with 500 Hz, 2 ms tone bursts and 0.1 ms clicks at intensities up to 142 dB peak SPL. Conventional VEMPs were recorded from the ipsilateral sternocleidomastoid muscle to determine threshold, and OVEMPs were recorded from electrode pairs placed superior and inferior to the eyes. Three-dimensional eye movements were measured with scleral dual-search coils.Results:In patients with SCD, OVEMP amplitudes were significantly larger than normal (p