Superior Canal Dehiscence 

  • Author: Wayne T Shaia, MD; Chief Editor: Arlen D Meyers, MD, MBA   more...
 
Updated: Sep 30, 2011
 

Background

Superior canal dehiscence syndrome (SCDS) is a newly described condition in which vestibular symptoms are elicited by sound or pressure secondary to a dehiscent superior semicircular canal. More than 70 years have passed since Tullio and Hennebert described their findings of sound-induced and pressure-induced vestibular activation.

Since then, the Tullio phenomenon, wherein vestibular symptoms are induced by loud sounds, has been associated with syphilis, perilymphatic fistula, congenital deafness, Ménière disease, head trauma, Lyme disease, cholesteatomas with labyrinthine fistula, and fenestration operations. The Hennebert sign of vestibular symptoms due to changes in external auditory canal pressure is frequently found in conjunction with the Tullio phenomenon (as in perilymphatic fistula, syphilis, Ménière disease).

In 2000, Minor found a series of patients with positive Tullio and Hennebert signs.[1] He was the first to relate these positive findings directly to an anatomical defect of the superior semicircular canal that was detected with high-resolution computed tomography (HRCT). Minor theorized that, when the bone over the canal becomes thin or dehiscent, it acts as an additional window for the vestibular system, allowing pressure and noise changes to induce vestibular activity. SCDS, as it has become known, is now recognized and treated by otolaryngologists and neurootologists throughout the world.

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Pathophysiology

The cochleovestibular system has 2 functional windows. The oval window, which houses the footplate of the stapes, allows sound to enter the inner ear (vestibule) and to be carried via hydroacoustic waves through the perilymph. This allows the mechanical wave to be transduced into neural activity, and, thus, sound is perceived.

The function of the round window is more controversial. It is thought to have several roles. Its first role is thought to involve the release of sound and mechanical energy from the scala tympani. Another proposed role is its participation in the secretion and absorption of substances in the inner ear. The round window may also play a role as a defense mechanism of the inner ear.

These 2 windows of the inner ear work together to regulate hearing and balance. When a dehiscence in the superior semicircular canal is created, a third-window effect is thought to take place. As a result, endolymph within the labyrinthine system continues to move in relation to sound or pressure, which causes an activation of the vestibular system. The intracranial pressure transmission to the round window may also result in increased compliance of the inner ear from stretching of the round window membrane. This pressure transmission may also result in a frank round window (or oval window) fistula.

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Epidemiology

Frequency

United States

The true incidence of persons with symptomatic SCDS is currently unknown. One study of 1000 cadaveric temporal bones revealed that a dehiscence of bone that overlies the superior canal was present in approximately 0.5% of temporal bone specimens. In an additional 1.4% of the specimens, the bone was markedly thin (≤ 0.1 mm) compared with the normal bone.

Race

SCDS has no racial bias.

Sex

SCDS appears to affect males and females equally.

Age

In 2000, Minor reported that, in his original series of 17 patients, the median age at diagnosis was 40 years (range, 27-70 y).[1]

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Contributor Information and Disclosures
Author

Wayne T Shaia, MD  Consulting Staff, Department of Otology/Neurotology, Medical College of Virginia

Disclosure: Nothing to disclose.

Coauthor(s)

Jack M Kartush  MD, Clinical Professor, Department of Otolaryngology, Wayne State University School of Medicine; Director of Otology Neurotology and Skull Base Surgery, Providence Hospital; President, Michigan Ear Institute; President, American NeuroMonitoring

Jack M Kartush is a member of the following medical societies: American Academy of Otolaryngology-Head and Neck Surgery, American Neurotology Society, and American Otological Society

Disclosure: Nothing to disclose.

Angela Shu-Yuen Peng, MD  Resident Physician, Department of Otolaryngology/Head and Neck Surgery, Virginia Commonwealth University Medical Center

Angela Shu-Yuen Peng, MD is a member of the following medical societies: American Academy of Otolaryngology-Head and Neck Surgery, American Medical Association, and Virginia Society of Otolaryngology-Head and Neck Surgery

Disclosure: Nothing to disclose.

Specialty Editor Board

Robert A Battista, MD, FACS  Assistant Professor of Otolaryngology, Northwestern University Medical School; Physician, Ear Institute of Chicago, LLC

Robert A Battista, MD, FACS is a member of the following medical societies: American Academy of Otolaryngology-Head and Neck Surgery, American College of Surgeons, American Neurotology Society, and Illinois State Medical Society

Disclosure: Nothing to disclose.

Francisco Talavera, PharmD, PhD  Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Medscape Salary Employment

Gerard J Gianoli, MD  Clinical Associate Professor, Department of Otolaryngology-Head and Neck Surgery, Tulane University School of Medicine; Vice President, The Ear and Balance Institute; Chief Executive Officer, Ponchartrain Surgery Center

Gerard J Gianoli, MD is a member of the following medical societies: American Academy of Otolaryngology-Head and Neck Surgery, American College of Surgeons, American Neurotology Society, American Otological Society, Society of University Otolaryngologists-Head and Neck Surgeons, and Triological Society

Disclosure: Vesticon, Inc. None Board membership

Christopher L Slack, MD  Private Practice in Otolaryngology and Facial Plastic Surgery, Associated Coastal ENT; Medical Director, Treasure Coast Sleep Disorders

Christopher L Slack, MD is a member of the following medical societies: Alpha Omega Alpha, American Academy of Facial Plastic and Reconstructive Surgery, American Academy of Otolaryngology-Head and Neck Surgery, and American Medical Association

Disclosure: Nothing to disclose.

Chief Editor

Arlen D Meyers, MD, MBA  Professor, Department of Otolaryngology-Head and Neck Surgery, University of Colorado School of Medicine

Arlen D Meyers, MD, MBA is a member of the following medical societies: American Academy of Facial Plastic and Reconstructive Surgery, American Academy of Otolaryngology-Head and Neck Surgery, and American Head and Neck Society

Disclosure: Covidien Corp Consulting fee Consulting; US Tobacco Corporation Unrestricted gift Unknown; Axis Three Corporation Ownership interest Consulting; Omni Biosciences Ownership interest Consulting; Sentegra Ownership interest Board membership; Syndicom Ownership interest Consulting; Oxlo Consulting; Medvoy Ownership interest Management position; Cerescan Imaging Honoraria Consulting; GYRUS ACMI Honoraria Consulting

References

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  2. Tsunoda A, Terasaki O. Dehiscence of the bony roof of the superior semicircular canal in the middle cranial fossa. J Laryngol Otol. Jul 2002;116(7):514-8. [Medline].

  3. Brantberg K, Verrecchia L. Testing vestibular-evoked myogenic potentials with 90-dB clicks is effective in the diagnosis of superior canal dehiscence syndrome. Audiol Neurootol. Sep 2009;14(1):54-8. [Medline].

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  8. Gianoli GJ, Soileau JS. The dehiscent middle fossa: prevalence, manifestations, associated findings and results of 24 surgical explorations for superior semicircular canal dehiscence. Publication pending: presented as triologic thesis, 2005.

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  17. Martin JE, Neal CJ, Monacci WT, Eisenman DJ. Superior semicircular canal dehiscence: a new indication for middle fossa craniotomy. Case report. J Neurosurg. Jan 2004;100(1):125-7. [Medline].

  18. Merchant SN, Rosowski JJ, McKenna MJ. Superior semicircular canal dehiscence mimicking otosclerotic hearing loss. Adv Otorhinolaryngol. 2007;65:137-45. 2007;65:137-45. [Medline].

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  28. Tullio P. Das Ohr und die Entstehung der Sprache und Schrift Berlin. Urban & Schwarzenberg,. 1929.

  29. [Best Evidence] [Guideline] Vlastarakos PV, Proikas K, Tavoulari E, Kikidis D, Maragoudakis P, Nikolopoulos TP. Efficacy assessment and complications of surgical management for superior semicircular canal dehiscence: a meta-analysis of published interventional studies. Eur Arch Otorhinolaryngol. FEB;266(2):177-86. [Medline].

 
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Coronal high-resolution computed tomography scan (1-mm sections) that demonstrates the presence of the superior semicircular canal (figure A, black arrow). As the scan is followed posteriorly (figures B, C, D), the bony dehiscence over the superior canal (black arrow) becomes more apparent.
 
 
 
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