Objective: To compare subjective and objective findings between patients with true dehiscence versus thin bone over the superior semicircular canal (SSC).
Study design: Retrospective case series.
Setting: Tertiary referral center.
Patients: All patients from our institution with true dehiscence or thin bone over the SSC on computed tomography temporal bone (oblique view) from 2007 to 2013.
Main outcome measures: Subjective test: Dizziness Handicap Inventory (DHI). Objective tests: Infrared video eye recording with varying stimuli (Tulio, Fistula, and Vibration); vestibular evoked myogenic potential (VEMP); electrocochleography; videonystagmography; pure-tone audiometry (i.e., air-bone gap).
Results: Fifty-four patients (64 ears) were reviewed. Thirty-nine patients (47 ears) had true dehiscence of the SSC on temporal bone computed tomography. Fifteen patients (17 ears) had thin bone over the SSC. There was no statistical difference in DHI scores for patients with true dehiscence versus those with thin bone over the SSC. Only cervical VEMP and air-bone gap via pure-tone audiometry revealed a significant difference between the two groups. The remaining vestibular assessments did not demonstrate any difference. No significant correlations were revealed between DHI and objective test findings across and within the two groups.
Conclusion: Among the objective tests, cervical VEMP and pure-tone audiometry are the only tools to distinguish between true dehiscence and thin bone over the SSC. DHI does not differentiate between these two groups. Furthermore, no correlation exists between DHI and any objective finding. Further investigation is necessary to develop a validated subjective symptom index of patients with SSC syndrome.