New model of superior semicircular canal dehiscence with reversible diagnostic findings characteristic of patients with the disorder
Third window syndrome is a vestibular-cochlear disorder in humans in which a third mobile window of the otic capsule creates changes to the flow of sound pressure energy through the perilymph/endolymph. The nature and location of this third mobile window can occur at many different sites (or multipl...
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| Published in: | Frontiers in neurology Vol. 13; p. 1035478 |
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| Main Authors: | , , , , , , , , |
| Format: | Journal Article |
| Language: | English |
| Published: |
Switzerland
Frontiers Media S.A
19-01-2023
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| Subjects: | |
| Online Access: | Get full text |
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| Summary: | Third window syndrome is a vestibular-cochlear disorder in humans in which a third mobile window of the otic capsule creates changes to the flow of sound pressure energy through the perilymph/endolymph. The nature and location of this third mobile window can occur at many different sites (or multiple sites); however, the most common third mobile window is superior semicircular canal dehiscence (SSCD). There are two essential objective diagnostic characteristics needed to validate a model of SSCD: the creation of a pseudoconductive hearing loss and cVEMP increased amplitude and decreased threshold.
Adult Mongolian gerbils (
= 36) received surgical fenestration of the superior semicircular canal of the left inner ear. ABR and c+VEMP testing were carried out prior to surgery and over acute (small 1 mm SSCD, 1-10 days) or prolonged (large 2 mm SSCD, 28 days) recovery. Because recovery of function occurred quickly, condenser brightfield stereomicroscopic examination of the dehiscence site was carried out for the small SSCD animals
and compared to both ABRs and c+VEMPs. Micro-CT analysis was also completed with representative samples of control, day 3 and 10 post-SSCD animals.
The SSCD created a significant worsening of hearing thresholds of the left ear; especially in the lower frequency domain (1-4 kHz). Left (EXP)/right (CTL) ear comparisons
ABR show significant worsening thresholds at the same frequency representations, which is a proxy for the human pseudoconductive hearing loss seen in SSCD. For the c+VEMP measurements, increased amplitude of the sound-induced response (N1 2.5 ms and P1 3.2 ms) was observed in animals that received larger fenestrations. As the bone regrew, the c+VEMP and ABR responses returned toward preoperative values. For small SSCD animals, micro-CT data show that progressive osteoneogenesis results in resurfacing of the SSCD without bony obliteration.
The large (2 mm) SSCD used in our gerbil model results in similar electrophysiologic findings observed in patients with SSCD. The changes observed also reverse and return to baseline as the SSCD heals by bone resurfacing (with the lumen intact). Hence, this model does not require a second surgical procedure to plug the SSCD. |
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| Bibliography: | ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 ORCID: P. Ashley Wackym orcid.org/0000-0002-2904-5072 Carey D. Balaban orcid.org/0000-0002-3570-3844 Reviewed by: Wei Gao, The Fourth Military Medical University, China; Erin Gillikin Piker, James Madison University, United States; Alexandre Bisdorff, Hospital Center Emile Mayrisch, Luxembourg This article was submitted to Neuro-Otology, a section of the journal Frontiers in Neurology Todd M. Mowery orcid.org/0000-0001-7727-6353 These authors share first authorship Edited by: Vincent Van Rompaey, University of Antwerp, Belgium |
| ISSN: | 1664-2295 1664-2295 |
| DOI: | 10.3389/fneur.2022.1035478 |