Semicircular Canal Function Before and After Surgery for Superior Canal Dehiscence

Superior canal dehiscence (SCD) is a defect in the bony covering of the superior semicircular canal. Patients with SCD present with a wide range of symptoms, including hearing loss, yet it is unknown whether hearing is affected by parameters such as the location of the SCD. Our previous human cadaveric temporal bone study, utilizing intracochlear pressure measurements, generally showed that an increase in dehiscence size caused a low-frequency monotonic decrease in the cochlear drive across the partition, consistent with increased hearing loss. This previous study was limited to SCD sizes including and smaller than 2 mm long and 0.7 mm wide. However, the effects of larger SCDs (>2 mm long) were not studied, although larger SCDs are seen in many patients. Therefore, to answer the effect of parameters that have not been studied, this present study assessed the effect of SCD location and the effect of large-sized SCDs (>2 mm long) on intracochlear pressures. We used simultaneous measurements of sound pressures in the scala vestibuli and scala tympani at the base of the cochlea to determine the sound pressure difference across the cochlear partition - a measure of the cochlear drive in a temporal bone preparation - allowing for assessment of hearing loss. We measured the cochlear drive before and after SCDs were made at different locations (e.g. closer to the ampulla of the superior semicircular canal or closer to the common crus) and for different dehiscence sizes (including larger than 2 mm long and 0.7 mm wide). Our measurements suggest the following: (1) different SCD locations result in similar cochlear drive and (2) larger SCDs produce larger decreases in cochlear drive at low frequencies. However, the effect of SCD size seems to saturate as the size increases above 2-3 mm long and 0.7 mm wide. Although the monotonic effect was generally consistent across ears, the quantitative amount of change in cochlear drive due to dehiscence size varied across ears. Additionally, the size of the dehiscence above which the effect on hearing saturated varied across ears. These findings show that the location of the SCD does not generally influence the amount of hearing loss and that SCD size can help explain some of the variability of hearing loss in patients. i 2014 S. Karger AG, Basel

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Semicircular Canal Function Before and After Surgery for Superior Canal Dehiscence

Otology & Neurotology ◽

10.1097/01.mao.0000253284.40995.d8 ◽

2007 ◽

Vol 28 (3) ◽

pp. 356-364 ◽

Cited By ~ 87

Author(s):

John P. Carey ◽

Americo A. Migliaccio ◽

Lloyd B. Minor

Keyword(s):

Semicircular Canal ◽

Superior Canal Dehiscence ◽

Before And After ◽

Canal Dehiscence

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Click-evoked vestibulo-ocular reflex

Neurology ◽

10.1212/01.wnl.0000204445.81884.c7 ◽

2006 ◽

Vol 66 (7) ◽

pp. 1079-1087 ◽

Cited By ~ 26

Author(s):

S. T. Aw ◽

M. J. Todd ◽

G. E. Aw ◽

J. S. Magnussen ◽

I. S. Curthoys ◽

...

Keyword(s):

Semicircular Canal ◽

Rotation Axis ◽

Head Orientation ◽

Superior Canal Dehiscence ◽

Ocular Reflex ◽

Eye Rotation ◽

Vestibulo Ocular Reflex ◽

Low Threshold ◽

Canal Dehiscence ◽

Click Polarity

Background: An enlarged, low-threshold click-evoked vestibulo-ocular reflex (VOR) can be averaged from the vertical electro-oculogram in a superior canal dehiscence (SCD), a temporal bone defect between the superior semicircular canal and middle cranial fossa.Objective: To determine the origin and quantitative stimulus–response properties of the click-evoked VOR.Methods: Three-dimensional, binocular eye movements evoked by air-conducted 100-microsecond clicks (110 dB normal hearing level, 145 dB sound pressure level, 2 Hz) were measured with dual-search coils in 11 healthy subjects and 19 patients with SCD confirmed by CT imaging. Thresholds were established by decrementing loudness from 110 dB to 70 dB in 10-dB steps. Eye rotation axis of click-evoked VOR computed by vector analysis was referenced to known semicircular canal planes. Response characteristics were investigated with regard to enhancement using trains of three to seven clicks with 1-millisecond interclick intervals, visual fixation, head orientation, click polarity, and stimulation frequency (2 to 15 Hz).Results: In subjects and SCD patients, click-evoked VOR comprised upward, contraversive-torsional eye rotations with onset latency of approximately 9 milliseconds. Its eye rotation axis aligned with the superior canal axis, suggesting activation of superior canal receptors. In subjects, the amplitude was less than 0.01°, and the magnitude was less than 3°/second; in SCD, the amplitude was up to 60 times larger at 0.66°, and its magnitude was between 5 and 92°/second, with a threshold 10 to 40 dB below normal (110 dB). The click-evoked VOR magnitude was enhanced approximately 2.5 times with trains of five clicks but was unaffected by head orientation, visual fixation, click polarity, and stimulation frequency up to 10 Hz; it was also present on the surface electro-oculogram.Conclusion: In superior canal dehiscence, clicks evoked a high-magnitude, low-threshold, 9-millisecond-latency vestibulo-ocular reflex that aligns with the superior canal, suggesting superior canal receptor hypersensitivity to sound.

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Costimulation of the Horizontal Semicircular Canal during Skull Vibrations in Superior Canal Dehiscence Syndrome

Audiology and Neurotology ◽

10.1159/000358002 ◽

2014 ◽

Vol 19 (3) ◽

pp. 175-183 ◽

Cited By ~ 8

Author(s):

Joo Hyun Park ◽

Hyo Jung Kim ◽

Ji-Soo Kim ◽

Ja-Won Koo

Keyword(s):

Semicircular Canal ◽

Horizontal Semicircular Canal ◽

Superior Canal Dehiscence ◽

Canal Dehiscence

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How I do it: underwater endoscopic ear surgery for plugging in superior canal dehiscence syndrome

The Journal of Laryngology & Otology ◽

10.1017/s0022215117001104 ◽

2017 ◽

Vol 131 (8) ◽

pp. 745-748 ◽

Cited By ~ 4

Author(s):

D Yamauchi ◽

Y Hara ◽

H Hidaka ◽

T Kawase ◽

Y Katori

Keyword(s):

Inner Ear ◽

Semicircular Canal ◽

Saline Water ◽

Mastoid Cavity ◽

Endoscopic Ear Surgery ◽

Ear Surgery ◽

Membranous Labyrinth ◽

Endoscopic View ◽

Superior Canal Dehiscence ◽

Canal Dehiscence

AbstractBackground:Underwater endoscopic ear surgery does not require suction and so protects the inner ear from unexpected aeration that may damage its function in the treatment of labyrinthine fistula. A method of underwater endoscopic ear surgery is proposed for the treatment of superior canal dehiscence.Methods:Underwater endoscopic ear surgery was performed for plugging of the superior semicircular canal through the transmastoid approach. Saline solution was infused into the mastoid cavity through an Endo-Scrub Lens Cleaning Sheath. The tip of the inserted endoscope was filled completely with saline water.Results:Using this underwater endoscopic view, the canal was clearly dissected to expose the semicircular canal membranous labyrinth and dehiscence area. No particular complication occurred during the surgical procedure.Conclusion:The underwater endoscopic ear surgery technique for plugging in superior canal dehiscence secures an excellent visual field and protects the inner ear from unexpected aeration.

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Transmastoid semicircular canal occlusion: A safe and highly effective treatment for benign paroxysmal positional vertigo and superior canal dehiscence

The Laryngoscope ◽

10.1002/lary.23390 ◽

2012 ◽

Vol 122 (8) ◽

pp. 1862-1866 ◽

Cited By ~ 66

Author(s):

Jason A. Beyea ◽

Sumit K. Agrawal ◽

Lorne S. Parnes

Keyword(s):

Effective Treatment ◽

Semicircular Canal ◽

Benign Paroxysmal Positional Vertigo ◽

Superior Canal Dehiscence ◽

Positional Vertigo ◽

Highly Effective ◽

Semicircular Canal Occlusion ◽

Canal Dehiscence ◽

Paroxysmal Positional Vertigo

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Dehiscence of Bone Overlying the Superior Semicircular Canal as a Cause of an Air-Bone Gap on Audiometry

American Journal of Audiology ◽

10.1044/1059-0889(2003/004) ◽

2003 ◽

Vol 12 (1) ◽

pp. 11-16 ◽

Cited By ~ 30

Author(s):

Kenneth M. Cox ◽

Daniel J. Lee ◽

John P. Carey ◽

Lloyd B. Minor

Keyword(s):

Hearing Loss ◽

High Resolution ◽

Middle Ear ◽

Semicircular Canal ◽

Conductive Hearing Loss ◽

Superior Canal Dehiscence ◽

High Resolution Ct ◽

Temporal Bones ◽

Conductive Hearing ◽

Canal Dehiscence

Dehiscence of bone overlying the superior semicircular canal can result in a syndrome of vertigo and oscillopsia induced by loud noises or by maneuvers that change middle ear or intracranial pressure. Patients with this disorder can also experience a heightened sensitivity to bone-conducted sounds in the presence of normal middle ear function. High-resolution CT scans of the temporal bones demonstrate the dehiscence. The authors describe a patient with bilateral superior canal dehiscence who had bilateral low-frequency conductive hearing loss, normal middle ear function, intact acoustic reflexes, and intact vestibular-evoked myogenic potentials. These findings would not be expected on the basis of a middle ear cause of the conductive hearing loss. A high-resolution CT scan of the temporal bones in this patient revealed bilateral superior canal dehiscence. Normal acoustic immittance findings in the presence of conductive hearing loss should alert clinicians to the possibility of inner ear cause of an air-bone gap due to superior canal dehiscence

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