Testing Vestibular-Evoked Myogenic Potentials with 90-dB Clicks Is Effective in the Diagnosis of Superior Canal Dehiscence Syndrome

Abstract

Vestibular-evoked myogenic potentials (VEMP) in response to 90-dB-nHL clicks were studied in 20 patients (22 ears) with superior canal dehiscence syndrome. Their amplitude was compared to the VEMP from the ‘unaffected’ ears of 113 patients using the same stimulus level. The 113 control subjects were those from a previous study on 1,000 patients who had had large VEMP amplitudes in response to 500-Hz 129-dB-SPL tone bursts, and, because of this, had been tested with 90-dB-nHL clicks (which are a much weaker sound stimulus than our routine 500-Hz tone burst). It was found that 90-dB-nHL clicks clearly distinguished patients with vestibular hypersensitivity to sounds. In patients, the VEMP amplitude was usually larger than the simultaneously recorded background electromyographic activity (i.e. ‘corrected’ amplitude >1), whereas this was not the case for the controls. Consequently, it is suggested that 90-dB-nHL clicks can be used to screen for vestibular hypersensitivity to sounds. This finding has clinical implications for patients with suspected Tullio phenomenon because the definitive VEMP test for this (i.e. estimation of VEMP threshold) is not only time-consuming, but there is also difficulty related to the low signal-to-noise ratio close to the threshold.