The relationship between the air-bone gap and the size of superior semicircular canal dehiscence
Received 7 May 2009; received in revised form 25 August 2009; accepted 31 August 2009. published online 02 November 2009.
Abstract
Objective
To examine the relationship between the air-bone gap (ABG) and the size of the superior semicircular canal dehiscence (SSCD) as measured on a computed tomography (CT) scan.
Study Design
Case series with chart review.
Setting
Tertiary referral center.
Patients
Twenty-three patients (28 ears) diagnosed with SSCD.
Main Outcome Measures
The size of the dehiscence on CT scans and the ABG on pure-tone audiometry were recorded.
Results
The size of the dehiscence ranged from 1.0 to 6.0 mm (mean, 3.5 ± 1.6 mm). Six ears with a dehiscence measuring less than 3.0 mm did not have an ABG (0 dB). The remaining 18 ears showed an average ABG at 500, 1000, and 2000 Hz (AvABG500-2000) ranging from 3.3 to 27.0 dB (mean, 11.6 ± 5.7 dB). The analysis of the relationship between the dehiscence size and AvABG500-2000 revealed a correlation of R2 = 0.828 (P < 0.001, quadratic fit) and R2 = 0.780 (P < 0.001, linear fit). Therefore, the larger the dehiscence, the larger the ABG at lower frequencies on pure-tone audiometry.
Conclusions
In SSCD patients, an ABG is consistently shown at the low frequency when the dehiscence is larger than 3 mm. The size of the average ABG correlates with the size of the dehiscence. These findings highlight the effect of the dehiscence size on conductive hearing loss in SSCD and contribute to a better understanding of the symptomatology of patients with SSCD.
aEar Science Institute Australia, Ear Sciences Centre, School of Surgery, University of Western Australia, and Department of Otolaryngology–Head and Neck Surgery, Sir Charles Gairdner Hospital, Nedlands, Western Australia, Australia
bPerth Radiological Clinic, Subiaco, Western Australia, Australia
Corresponding author: Heng-Wai Yuen, MBBS, MRCSE, MMed(ORL), DOHNS, Department of Otolaryngology–Head and Neck Surgery, Alexandra Hospital, 378 Alexandra Road, Singapore 159964, Republic of Singapore
No sponsorships or competing interests have been disclosed for this article.
ABSTRACT