Vestibular Evoked Myogenic Potential (VEMP) Testing for Diagnosis of Superior Semicircular Canal Dehiscence

Abstract

Superior semicircular canal dehiscence is a bony defect of the superior semicircular canal, which can lead to a variety of auditory and vestibular symptoms. The diagnosis of superior semicircular canal dehiscence (SCD) can be challenging, time consuming, and costly. The clinical presentation of SCD patients resembles that of other otologic disease, necessitating objective diagnostics. Although temporal bone CT imaging provides excellent sensitivity for SCD detection, it lacks specificity. Because the treatment of SCD is surgical, it is crucial to use a highly specific test to confirm the diagnosis and avoid false positives and subsequent unnecessary surgery. This review provides an update on recent improvements in vestibular evoked myogenic potential (VEMP) testing for SCD diagnosis. Combining audiometric and conventional cervical VEMP results improves SCD diagnostic accuracy. High frequency VEMP testing is superior to all other methods described to date. It is highly specific for the detection of SCD and may be used to guide decision-making regarding the need for subsequent CT imaging. This algorithmic sequential use of testing can substantially reduce radiation exposure as well as cost associated with SCD diagnosis.

A Simple Specific Functional Test for SCD: VEMPs to High Frequency (4,000Hz) Stimuli—Their Origin and Explanation

“…We fully agree with the statement by Noij et al (1) that for the detection of semicircular canal dehiscence (SCD) "High frequency VEMP testing is superior to all other methods described to date. It is highly specific for the detection of SCD and may be used to guide decision-making regarding the need for subsequent CT imaging" (1). The ideal is a very fast, innocuous test rather than extended and uncomfortable tests such as determining the threshold for VEMPs.…”

Current Trends, Controversies, and Future Directions in the Evaluation and Management of Superior Canal Dehiscence Syndrome

“…In oVEMP testing, the utricle is stimulated leading to activation of the contralateral eye muscles. The use of VEMP testing has increased to assess patients with a suspected third window, and many, but not all patients with SCDS, have lowered VEMP thresholds and increased VEMP amplitudes in response to an air-conduction stimulus (depending on selected cutoff values and study populations, cVEMP and oVEMP have a sensitivity and specificity above 70%) ( 59 , 60 ). A number of studies have demonstrated that the diagnostic utility of cVEMP thresholds and oVEMP amplitudes is better than the diagnostic utility of cVEMP amplitudes and oVEMP thresholds, when using a 500 Hz tone burst or a click stimuli ( 59 , 61 – 63 ).…”

“…Another initiative to improve the diagnostic accuracy of cVEMP was the use 2,000 Hz stimulus instead of the commonly used 500 Hz tone burst. By using a 2,000 Hz tone burst, the authors of the TWI were able to increase the sensitivity and specificity (sensitivity of 92% and specificity of 100% using TWI at 2 kHz vs. 88 and 100% using TWI at 500 Hz), and they furthermore showed that cVEMP amplitude (as a normalized peak-to-peak amplitude) generated superior results ( 60 , 66 ). High frequency stimuli in oVEMP testing has also shown to be effective in differentiating patients with SCDS from normal controls (one study found sensitivity of 83% and specificity of 93% using 4,000 Hz oVEMP responses vs. 62 and 73% using 500 Hz responses) ( 67 , 68 ).…”

“…VEMP responses are dependent on normal sound transmission to the oval window, which may not be the case if there is middle ear pathology, obscuring the SCD-related changes ( Figures 2 , 4 ). Second, VEMP responses decrease with age, although the SCD effect seems to dominate the age effect ( 60 ), and conversely, stronger sternocleidomastoid muscle contraction is correlated with larger cVEMP amplitude ( 60 ). Third, there is no known association between cVEMP thresholds and severity of auditory or vestibular symptoms ( 40 ).…”

“…Third, there is no known association between cVEMP thresholds and severity of auditory or vestibular symptoms ( 40 ). Finally, due to lack of standardization in measurement conditions, comparisons of VEMP data across institutions remains challenging and no standard cutoff values for threshold and amplitude exist ( 60 , 70 , 77 ).…”