A superior semicircular canal dehiscence syndrome multicenter study: is there an association between size and symptoms?

OBJECTIVE: The aim of this investigation was to determine if there is any association between the size of the canal dehiscences and the symptoms and signs of patients presenting with the superior semicircular canal dehiscence syndrome. STUDY DESIGN: Prospective multicenter study. SETTING: Tertiary referral center. PATIENTS: Twenty-seven patients, 14 females and 13 males, aged 25 to 83 years, coming from Switzerland, France, Belgium, or Italy, with dehiscence of the superior semicircular canal diagnosed by high-resolution computed tomographic scans of the temporal bone. INTERVENTIONS: Audiologic tests, a battery of vestibular tests (Tullio phenomenon, Hennebert sign, Valsalva maneuver), vestibular evoked myogenic potentials (VEMPs), and high-resolution computed tomographic scans of the temporal bone. MAIN OUTCOME MEASURES: Association between the symptoms/signs and the size of the superior canal dehiscence. RESULTS: Clinically patients could be divided into three different groups: Superior canal dehiscences (> or =2.5 mm) presented predominantly with cochleovestibular symptoms and/or signs (sensitivity, 91.7%; specificity, 70%), whereas smaller one's showed either cochlear or vestibular dysfunction. Patients with larger dehiscences were significantly more associated with vestibulocochlear symptoms/signs, lower VEMP thresholds, and objective vestibular findings (e.g., Tullio phenomenon) than subjects with smaller bony defects. No significant association between the size of the dehiscence and the audiogram pattern or individual findings could be found. The location of the dehiscence seemed to have no influence on the clinical manifestation and findings. CONCLUSION: Patients with larger superior canal dehiscences show significantly more vestibulocochlear symptoms/signs, lower VEMP thresholds, and objective vestibular findings compared with smaller ones. Smaller dehiscences mainly present with either cochlear or vestibular dysfunction.