A Single Fast Test for Semicircular Canal Dehiscence—oVEMP n10 to 4000 Hz—Depends on Stimulus Rise Time

Abstract

As previously reported, a single test measuring oVEMP n10 to 4000 Hz stimuli (bone-conducted vibration (BCV) or air-conducted sound (ACS)) provides a definitive diagnosis of semicircular canal dehiscence (SCD) in 22 CT-verified patients, with a sensitivity of 1.0 and specificity of 1.0. This single short screening test has great advantages of speed, minimizing testing time, and the exposure of patients to stimulation. However, a few studies of the 4000 Hz test for SCD have reported sensitivity and specificity values which are slightly less than reported previously. We hypothesized that the rise time of the stimulus is important for detecting the oVEMP n10 to 4000 Hz, similarly to what we had shown for 500 and 750 Hz BCV. We measured oVEMP n10 in 15 patients with CT-verified SCD in response to 4000 Hz ACS or BCV stimuli with rise times of 0, 1, and 2 ms. As a result, increasing the rise time of the stimulus reduced the oVEMP n10 amplitude. This outcome is expected from the physiological evidence of guinea pig primary vestibular afferents, which are activated by sound or vibration. Therefore, for clinical VEMP testing, short rise times are optimal (preferably 0 ms).

Development and Standardization of Modified Simultaneous Multifrequency Stimulus for Recording Ocular Vestibular-Evoked Myogenic Potential and Its Interaction with the Alternate Electrode Montages

“…semicircular canal afferent neurons in the normally encased labyrinths [26]. In our study, the response rate for a 4000 Hz tone burst, when using mSiMFy (∼6%), was very similar to the NSM-oVEMP.…”

“…SiMFy stimulus was claimed to obtain the frequency tuning of oVEMP without compromising the outcome obtained through the non-simultaneous multifrequency oVEMP (NSM-oVEMP) [oVEMPs recorded in response to multiple frequencies presented one after the completion of the other] with better test-retest reliability. However, this stimulus had the limitation of not including 4000 Hz, a frequency vital to the diagnosis of Superior semicircular canal dehiscence (SCDS) [25][26][27][28][29]. Therefore, there is a need to develop and standardize a modified SiMFy (mSiMFy) stimulus with the inclusion of 4000 Hz for recording ocular VEMP to further enhance its utility.…”