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KMID : 0858620070110010017
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Korean Journal of Audiology
2007 Volume.11 No. 1 p.17 ~ p.21
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Auditory Manifestation of Superior Semicircular Canal Dehiscence Syndrome
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Koo Ja-Won
Hong Sung-Kwang
Kim Ji-Soo
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Abstract
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Background and Objectives : Dehiscence of bone overlying the superior semicircular canal may produce both vestibular and auditory manifestations (superior semicircular canal dehiscence syndrome, SCDS). Since clinical manifestations are usually focused on sound and pressure induced vertigo and disequlibrium, authors reviewed cases of SCDS with emphasis on auditory manifestations and audiologic tests.
Materials and Methods : Medical records of 3 SCD patients were reviewed retrospectively. Audiologic evaluation included pure tone audiometry, impedance audiometry, vestibular evoked myogenic potentials (VEMP) and electrocochleography. Size of the dehiscence was measured on reconstructed image in the plane of the superior semicircular canal.
Results: Main auditory symptoms were ear fullness, tinnitus and hyperacusis than subjective hearing loss. Air-bone gap was increased more in lower frequencies than in higher frequencies. Threshold of VEMP test was lower in the affected ear by 15 to 20 dB and summation potential to action potential (SP/AP) ratio on electrocochleography was markedly increased in 2 tested patients.
Conclusion: Since vague ear symptoms such as ear fullness, hyperacusis, tinnitus were more predominent than hearing loss, high index of suspicion is important in the diagnosis of SCDS. Lowered VEMP threshold and increased SP/AP ratio seems to be the result of third window in the superior semicircular canal.
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KEYWORD
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Superior semicircular canal dehiscence syndrome, Tinnitus, Autophony, Ear fullness, Audiometry
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