Ocular vestibular evoked myogenic potential late peaks are enhanced in superior canal dehiscence and prolonged in vestibular migraine

BackgroundThe ocular vestibular evoked myogenic potential (oVEMP) n1 peak is the first of many that form part of the oscillating waveform. Previous work showed that up to 5 peaks can be elicited when an intact labyrinth is stimulated, with larger peaks contralaterally.ObjectiveWe investigated what happens to these later peaks when the n1 amplitude is enlarged, which is typically seen in superior canal dehiscence (SCD) and sometimes vestibular migraine (VM).MethodsWe measured oVEMPs elicited to air- (AC) and bone-conducted (BC) stimuli in 14 patients with SCD, 20 with SCD and classical migraine, 26 with clinically definite VM, and 20 with clinically definite VM and enlarged n1 peaks. We compared these results to 49 healthy volunteers.ResultsBoth groups of SCD patients had the largest peaks, but the same number of peaks as healthy volunteers (maximum 4 for AC; 5 for BC). In contrast, patients with VM had more later peaks than other groups (maximum 6 for both stimuli).ConclusionsAs the patients with the largest amplitudes did not have prolonged oscillation in their waveforms, our results suggest that the oscillation may be enhanced by central processes, such as lack of habituation that is reported in patients with VM.