Assessing ocular vestibular evoked myogenic potential (oVEMP) amplitudes is a useful method for screening for atypical superior canal dehiscence cases: A report of 2 cases

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We report herein on 2 patients with superior canal dehiscence (SCD), who did not exhibit the typical sound- or pressure-induced vestibular signs of the condition. In these patients, ocular VEMP (oVEMP) testing using air-conducted sound (ACS) was found to be useful for selecting patients for CT scan of the temporal bone. The first patient was a 38-year-old woman. She presented with a complaint of episodic vertigo and right aural fullness. She showed air-bone gaps at low frequencies in pure-tone audiometry on the right. She did not show sound- or pressure-induced vestibular signs. She showed augmentation of amplitudes and lowering of thresholds of cervical VEMP (cVEMP) and oVEMP to ACS 500 Hz short tone bursts (STB) on the right. CT scan images revealed superior (anterior) canal dehiscence on the right. The second patient was a 47-year-old man. He visited our clinic due to autophony and dizziness. He showed normal pure-tone hearing. He did not show sound- or pressure-induced vestibular signs. He showed bilateral augmentation of amplitudes of cVEMP and oVEMP to ACS 500 Hz STB. CT scan images revealed bilateral superior canal dehiscence. Augmentation was more prominent in oVEMP than cVEMP. These results suggest that oVEMP 500 Hz STB of ACS is a good method for screening for SCD.