Third Mobile Window Syndromes: New Insights in Pathomechanisms, Instrumental Diagnosis and Surgical Treatment

A special issue of Audiology Research (ISSN 2039-4349).

Deadline for manuscript submissions: 31 July 2024 | Viewed by 8709

Special Issue Editors


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Guest Editor
ENT Unit, Department of Surgery, Azienda USL—IRCCS di Reggio Emilia, Reggio Emilia, Italy
Interests: neurotology; inner ear; vestibular disease; BPPV; Meniere’s disease; vestibular migraine; acute vestibular loss; canal dehiscence; sudden hearing loss; video-HIT; VEMPs
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Guest Editor
Department of Otolaryngology-Head and Neck Surgery, Johns Hopkins University School of Medicine, Baltimore, MD, USA
Interests: vestibular; inner ear; third mobile window; bilateral vestibulopathy; eustachian tube; MRI; CT; imaging

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Guest Editor
Department of Otorhinolaryngology and Head and Neck Surgery, Maastricht University Medical Centre, Maastricht, The Netherlands
Interests: vestibular; inner ear; third mobile window

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Co-Guest Editor
MSA ENT Academy Center, Cassino, FR, Italy
Interests: otoneurology; vestibular system; ocular VEMPs; cervical VEMPs; vestibulo-ocular reflex (VOR); video-HIT; otolith system; eye movements (ocular torsion)
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Since the first description of superior canal dehiscence syndrome (SCDS) in 1998, an abundance of basic science and clinical research has supported modeling an additional opening in the inner ear as a third mobile window (TMW). Bony defects in the otic capsule bone such as over the superior semicircular canal result in a new low-impedance pathway in the inner ear for sound and pressure stimuli, accounting for several audio-vestibular symptoms and signs. The general term TMW syndrome has then been extended to a variety of abnormalities of the otic capsule sharing a similar clinical spectrum, such as enlarged vestibular aqueduct and dehiscences of the posterior and horizontal semicircular canals, cochlea and facial nerve. Beyond findings of sound/pressure-induced vertigo and nystagmus, low-frequency negative bone conduction thresholds on audiometry and enhanced vestibular-evoked myogenic potential (VEMP) responses, a wider range of atypical symptoms and abnormalities on clinical testing has been reported. Some physiologic and clinical aspects of TMW syndromes remain incompletely understood. Furthermore, consensus on the most effective surgical treatment is lacking.

The aim of this special Issue is to generate insights about clinical presentation, diagnosis and treatments strategies for TMW syndrome disorders, uncovering mechanisms of pathophysiology, and emphasizing differential diagnosis and outcomes following interventions. Original research manuscripts and reviews relevant to TMW syndromes are welcome.

Dr. Andrea Castellucci
Dr. Bryan Kevin Ward
Dr. Raymond Van De Berg
Dr. Leonardo Manzari
Guest Editors

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Keywords

  • third window syndrome
  • canal dehiscence
  • Tullio phenomenon
  • conductive hearing loss
  • enlarged vestibular aqueduct
  • labyrinthine fistula
  • vestibular-evoked myogenic potentials
  • video-head impulse test
  • vestibulo-ocular reflex

Published Papers (6 papers)

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Research

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14 pages, 4263 KiB  
Article
Otic Capsule Dehiscences Simulating Other Inner Ear Diseases: Characterization, Clinical Profile, and Follow-Up—Is Ménière’s Disease the Sole Cause of Vertigo and Fluctuating Hearing Loss?
by Joan Lorente-Piera, Carlos Prieto-Matos, Raquel Manrique-Huarte, Octavio Garaycochea, Pablo Domínguez and Manuel Manrique
Audiol. Res. 2024, 14(2), 372-385; https://doi.org/10.3390/audiolres14020032 - 12 Apr 2024
Viewed by 539
Abstract
Introduction: We present a series of six cases whose clinical presentations exhibited audiovestibular manifestations of a third mobile window mechanism, bearing a reasonable resemblance to Ménière’s disease and otosclerosis. The occurrence of these cases in such a short period has prompted a review [...] Read more.
Introduction: We present a series of six cases whose clinical presentations exhibited audiovestibular manifestations of a third mobile window mechanism, bearing a reasonable resemblance to Ménière’s disease and otosclerosis. The occurrence of these cases in such a short period has prompted a review of the underlying causes of its development. Understanding the pathophysiology of third mobile window syndrome and considering these entities in the differential diagnosis of conditions presenting with vertigo and hearing loss with slight air-bone gaps is essential for comprehending this group of pathologies. Materials and Methods: A descriptive retrospective cohort study of six cases diagnosed at a tertiary center. All of them went through auditive and vestibular examinations before and after a therapeutic strategy was performed. Results: Out of 84 cases of dehiscences described in our center during the period from 2014 to 2024, 78 belonged to superior semicircular canal dehiscence, while 6 were other otic capsule dehiscences. Among these six patients with a mean age of 47.17 years (range: 18–73), all had some form of otic capsule dehiscence with auditory and/or vestibular repercussions, measured through hearing and vestibular tests, with abnormalities in the results in five out of six patients. Two of them were diagnosed with Ménière’s disease (MD). Another two had cochleo-vestibular hydrops without meeting the diagnostic criteria for MD. In two cases, the otic capsule dehiscence diagnosis resulted from an intraoperative complication due to a gusher phenomenon, while in one case, it was an accidental radiological finding. All responded well to the proposed treatment, whether medical or surgical, if needed. Conclusions: Otic capsule dehiscences are relatively new and unfamiliar entities that should be considered when faced with cases clinically suggestive of Ménière’s disease, with discrepancies in complementary tests or a poor response to treatment. While high-sensitivity and specificity audiovestibular tests exist, completing the study with imaging, especially petrous bone CT scans, is necessary to locate and characterize the otic capsule defect responsible for the clinical presentation. Full article
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19 pages, 1854 KiB  
Article
Impaired Vestibulo-Ocular Reflex on Video Head Impulse Test in Superior Canal Dehiscence: “Spontaneous Plugging” or Endolymphatic Flow Dissipation?
by Andrea Castellucci, Pasquale Malara, Salvatore Martellucci, Mohamad Alfarghal, Cristina Brandolini, Gianluca Piras, Enrico Armato, Rosanna Rita Ruberto, Pasquale Brizzi, Livio Presutti and Angelo Ghidini
Audiol. Res. 2023, 13(5), 802-820; https://doi.org/10.3390/audiolres13050071 - 20 Oct 2023
Cited by 1 | Viewed by 1136
Abstract
Surgical plugging of the superior semicircular canal (SSC) represents an effective procedure to treat disabling symptoms in superior canal dehiscence (SCD), despite resulting in an impaired vestibulo-ocular reflex (VOR) gain for the SSC. On the other hand, SSC hypofunction on video head impulse [...] Read more.
Surgical plugging of the superior semicircular canal (SSC) represents an effective procedure to treat disabling symptoms in superior canal dehiscence (SCD), despite resulting in an impaired vestibulo-ocular reflex (VOR) gain for the SSC. On the other hand, SSC hypofunction on video head impulse test (vHIT) represents a common finding in patients with SCD exhibiting sound/pressure-induced vertigo, a low-frequency air–bone gap (ABG), and enhanced vestibular-evoked myogenic potentials (VEMPs). “Spontaneous canal plugging” has been assumed as the underlying process. Nevertheless, missing/mitigated symptoms and/or near-normal instrumental findings would be expected. An endolymphatic flow dissipation has been recently proposed as an alternative pathomechanism for SSC VOR gain reduction in SCD. We aimed to shed light on this debate by comparing instrumental findings from 46 ears of 44 patients with SCD exhibiting SSC hypofunction with post-operative data from 10 ears of 10 patients with SCD who underwent surgical plugging. While no difference in SSC VOR gain values was found between the two groups (p = 0.199), operated ears developed a posterior canal hypofunction (p = 0.002). Moreover, both ABG values (p = 0.012) and cervical/ocular VEMP amplitudes (p < 0.001) were significantly higher and VEMP thresholds were significantly lower (p < 0.001) in ears with SCD compared to operated ears. According to our data, canal VOR gain reduction in SCD should be considered as an additional sign of a third window mechanism, likely due to an endolymphatic flow dissipation. Full article
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11 pages, 1690 KiB  
Article
Cochlear Aqueduct Morphology in Superior Canal Dehiscence Syndrome
by Nimesh V. Nagururu, Diane Jung, Ferdinand Hui, Monica S. Pearl, John P. Carey and Bryan K. Ward
Audiol. Res. 2023, 13(3), 367-377; https://doi.org/10.3390/audiolres13030032 - 15 May 2023
Cited by 1 | Viewed by 1336
Abstract
The cochlear aqueduct (CA) connects the scala tympani to the subarachnoid space and is thought to assist in pressure regulation of perilymph in normal ears, however, its role and variation in inner ear pathology, such as in superior canal dehiscence syndrome (SCDS), is [...] Read more.
The cochlear aqueduct (CA) connects the scala tympani to the subarachnoid space and is thought to assist in pressure regulation of perilymph in normal ears, however, its role and variation in inner ear pathology, such as in superior canal dehiscence syndrome (SCDS), is unknown. This retrospective radiographic investigation compared CA measurements and classification, as measured on flat-panel computerized tomography, among three groups of ears: controls, n = 64; anatomic superior canal dehiscence without symptoms (SCD), n = 28; and SCDS, n = 64. We found that in a multinomial logistic regression adjusted for age, sex, and BMI, an increase in CA length by 1 mm was associated with a lower odds for being in the SCDS group vs. control (Odds ratio 0.760 p = 0.005). Hierarchical clustering of continuous CA measures revealed a cluster with small CAs and a cluster with large CAs. Another multinomial logistic regression adjusted for the aforementioned clinical covariates showed an odds ratio of 2.97 for SCDS in the small CA cluster as compared to the large (p = 0.004). Further, no significant association was observed between SCDS symptomatology—vestibular and/or auditory symptoms—and CA structure in SCDS ears. The findings of this study lend support to the hypothesis that SCDS has a congenital etiology. Full article
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Review

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20 pages, 6246 KiB  
Review
Skull Vibration-Induced Nystagmus in Superior Semicircular Canal Dehiscence: A New Insight into Vestibular Exploration—A Review
by Georges Dumas, Ian Curthoys, Andrea Castellucci, Laurent Dumas, Laetitia Peultier-Celli, Enrico Armato, Pasquale Malara, Philippe Perrin and Sébastien Schmerber
Audiol. Res. 2024, 14(1), 96-115; https://doi.org/10.3390/audiolres14010009 - 22 Jan 2024
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Abstract
The third window syndrome, often associated with the Tullio phenomenon, is currently most often observed in patients with a superior semicircular-canal dehiscence (SCD) but is not specific to this pathology. Clinical and vestibular tests suggestive of this pathology are not always concomitantly observed [...] Read more.
The third window syndrome, often associated with the Tullio phenomenon, is currently most often observed in patients with a superior semicircular-canal dehiscence (SCD) but is not specific to this pathology. Clinical and vestibular tests suggestive of this pathology are not always concomitantly observed and have been recently complemented by the skull-vibration-induced nystagmus test, which constitutes a bone-conducted Tullio phenomenon (BCTP). The aim of this work was to collect from the literature the insights given by this bedside test performed with bone-conducted stimulations in SCD. The PRISMA guidelines were used, and 10 publications were included and analyzed. Skull vibration-induced nystagmus (SVIN), as observed in 55 to 100% of SCD patients, usually signals SCD with greater sensitivity than the air-conducted Tullio phenomenon (ACTP) or the Hennebert sign. The SVIN direction when the test is performed on the vertex location at 100 Hz is most often ipsilaterally beating in 82% of cases for the horizontal and torsional components and down-beating for the vertical component. Vertex stimulations are more efficient than mastoid stimulations at 100 Hz but are equivalent at higher frequencies. SVIN efficiency may depend on stimulus location, order, and duration. In SCD, SVIN frequency sensitivity is extended toward high frequencies, with around 400 Hz being optimal. SVIN direction may depend in 25% on stimulus frequency and in 50% on stimulus location. Mastoid stimulations show frequently diverging results following the side of stimulation. An after-nystagmus observed in 25% of cases can be interpreted in light of recent physiological data showing two modes of activation: (1) cycle-by-cycle phase-locked activation of action potentials in SCC afferents with irregular resting discharge; (2) cupula deflection by fluid streaming caused by the travelling waves of fluid displacement initiated by sound or vibration at the point of the dehiscence. The SVIN direction and intensity may result from these two mechanisms’ competition. This instability explains the SVIN variability following stimulus location and frequency observed in some patients but also discrepancies between investigators. SVIN is a recent useful insight among other bedside examination tests for the diagnosis of SCD in clinical practice. Full article
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11 pages, 3035 KiB  
Review
Hearing Results after Transmastoid Superior Semicircular Canal Plugging for Superior Semicircular Canal Dehiscence: A Meta-Analysis
by Efterpi Michailidou, Pascal Oliver Rüegg, Tanya Karrer, Athanasia Korda, Stefan Weder, Martin Kompis, Marco Caversaccio and Georgios Mantokoudis
Audiol. Res. 2023, 13(5), 730-740; https://doi.org/10.3390/audiolres13050065 - 8 Oct 2023
Viewed by 1272
Abstract
Objective: The transmastoid plugging of a superior semicircular canal is considered a safe and effective technique for the management of superior semicircular canal dehiscence (SSCD). The aim of this meta-analysis is to assess the postoperative hearing outcomes after the transmastoid plugging of the [...] Read more.
Objective: The transmastoid plugging of a superior semicircular canal is considered a safe and effective technique for the management of superior semicircular canal dehiscence (SSCD). The aim of this meta-analysis is to assess the postoperative hearing outcomes after the transmastoid plugging of the superior semicircular canal. Search method and data sources: A systematic database search was performed on the following databases until 30 January 2023: MEDLINE, Embase, Cochrane Library, Web of Science, CINAHL, ICTRP, and clinicaltrials.gov. A systematic literature review and meta-analysis of the pooled data were conducted. We also included a consecutive case series with SCDS for those who underwent transmastoid plugging treatment at our clinic. Results: We identified 643 citations and examined 358 full abstracts and 88 full manuscripts. A total of 16 studies were eligible for the systematic review and 11 studies for the meta-analysis. Furthermore, 159 ears (152 patients) were included. The postoperative mean air conduction threshold remained unchanged (mean difference, 2.89 dB; 95% CI: −0.05, 5.84 dB, p = 0.58), while the mean bone conduction threshold was significantly worse (mean difference, −3.53 dB; 95% CI, −6.1, −0.95 dB, p = 0.9). Conclusion: The transmastoid plugging technique for superior semicircular canal dehiscence syndrome, although minimally worsening the inner ear threshold, is a safe procedure in terms of hearing preservation and satisfactory symptom relief. Full article
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13 pages, 1501 KiB  
Review
A Review of Neural Data and Modelling to Explain How a Semicircular Canal Dehiscence (SCD) Causes Enhanced VEMPs, Skull Vibration Induced Nystagmus (SVIN), and the Tullio Phenomenon
by Ian S. Curthoys, Christopher M. Smith, Ann M. Burgess and Julia Dlugaiczyk
Audiol. Res. 2023, 13(3), 418-430; https://doi.org/10.3390/audiolres13030037 - 2 Jun 2023
Cited by 4 | Viewed by 1926
Abstract
Angular acceleration stimulation of a semicircular canal causes an increased firing rate in primary canal afferent neurons that result in nystagmus in healthy adult animals. However, increased firing rate in canal afferent neurons can also be caused by sound or vibration in patients [...] Read more.
Angular acceleration stimulation of a semicircular canal causes an increased firing rate in primary canal afferent neurons that result in nystagmus in healthy adult animals. However, increased firing rate in canal afferent neurons can also be caused by sound or vibration in patients after a semicircular canal dehiscence, and so these unusual stimuli will also cause nystagmus. The recent data and model by Iversen and Rabbitt show that sound or vibration may increase firing rate either by neural activation locked to the individual cycles of the stimulus or by slow changes in firing rate due to fluid pumping (“acoustic streaming”), which causes cupula deflection. Both mechanisms will act to increase the primary afferent firing rate and so trigger nystagmus. The primary afferent data in guinea pigs indicate that in some situations, these two mechanisms may oppose each other. This review has shown how these three clinical phenomena—skull vibration-induced nystagmus, enhanced vestibular evoked myogenic potentials, and the Tullio phenomenon—have a common tie: they are caused by the new response of semicircular canal afferent neurons to sound and vibration after a semicircular canal dehiscence. Full article
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