A Comparison of Two Recording Montages for Ocular Vestibular Evoked Myogenic Potentials in Patients with Superior Canal Dehiscence Syndrome

Objective: The purpose of this investigation was to evaluate the sensitivity and specificity of the ocular vestibular evoked myogenic potential (oVEMP) using two electrode montages in patients with confirmed unilateral superior semicircular canal dehiscence syndrome (SCDS). Study Design: This study evaluated oVEMP response characteristics measured using two different electrode montages from 12 unilateral SCDS ears and 36 age-matched control ears (age range = 23-66). The oVEMP responses were elicited using 500 Hz tone-burst air conduction stimuli presented at an intensity of 95 dB nHL and a rate of 5.1/sec. The two electrode montages used are described as an "infraorbital" montage and a "belly-tendon" montage. Setting: Balance function laboratory embedded in a large, tertiary care otology clinic. Results: The belly-tendon electrode montage resulted in significantly larger amplitude responses than the infraorbital electrode montage for the ears with SCDS and the normal control ears. For both electrode montages the ear with SCDS exhibited a significantly larger amplitude response, 50% larger than the response amplitude from the normal control ear. The belly-tendon montage additionally produced larger median increases in amplitude compared with the infraorbital montage. Specifically, the median increase in oVEMP N1-P1 amplitudes using the belly-tendon montage was 39% greater in control ears, 76% greater in the SCDS ears, and 17% greater in the contralateral SCDS ears. Conclusions: The belly-tendon electrode montage yields significantly larger oVEMP amplitude responses for participants with SCDS and normal control participants.