Hearing loss in patients with enlarged vestibular aqueduct: Air-bone gap and audiological Bing test

Correlation Between Air-Bone Gap and Vestibular Aqueduct Size in Enlarged Vestibular Aqueduct Syndrome: A Systematic Review

The purpose of this review was to evaluate the air-bone gap with vestibular aqueduct size in enlarged vestibular aqueduct syndrome. According to the PRISMA guidelines we conducted a systematic review of the literature. Published international articles in English from 2000 to 2022 were screened, checking for studies that evaluated the air-bone gap of patients affected by enlarged vestibular aqueduct syndrome and the size of vestibular aqueduct. Data related to the hearing assessment and imaging investigation of enrolled participants were extracted. The chosen primary outcome measure was the correlation between air-bone-gap and vestibular aqueduct size. The database search allowed us to screen 485 articles and to select 5 articles discussing this topic for a total of 349 patients. Two studies showed a positive correlation between air-bone gap and vestibular aqueduct size, one only a trend and two no correlation. To date, it is not possible to draw conclusions whether or not there is a positive correlation between air-bone gap and vestibular aqueduct size in enlarged vestibular aqueduct syndrome. Higher quality studies would be conducted with standardized outcome measures to clarify the specific research question.

Conductive hearing loss in large vestibular aqueduct syndrome -clinical observations and proof-of-concept predictive modeling by a biomechanical approach

OBJECTIVE

The purpose of this study was to investigate the effect of a dilated vestibular aqueduct on conductive hearing loss (CHL). A biomechanical method was proposed for modeling the patterns of CHL in patients with large vestibular aqueduct syndrome (LVAS).

STUDY DESIGN

High resolution computed tomography (CT) scans and pure tone audiometry (PTA) were retrospectively collected from 16 patients who were diagnosed with LVAS. Seventeen ears with measurable air-bone gaps (ABGs) on PTA were applied for model development. The sizes of midpoint, operculum and distal segment were measured from CT to calculate the biomechanical parameters of each vestibular aqueduct. The mechanical effect of the dilated vestibular aqueduct on sound conduction was simulated using a lumped-parameter model. The CHL levels predicted by the model were compared with the observed ABGs at 250, 500 and 1000 Hz respectively.

RESULTS

The model was able to predict the trend that greater ABGs occurred at lower frequencies, which were consistent with clinical observations. However, deviations between the predicted and the observed ABGs became larger as the frequency increased. None of the correlation coefficients between the radiologic measures and the observed ABG levels were significant.

CONCLUSION

These findings lend support to the feasibility of this approach in modeling CHL in LVAS. The presence of a dilated vestibular aqueduct leads to altered impedance and sound pressure, suggesting the impact of a pathological third window. High individual variability of the observed ABGs implies additional factors may also be involved, especially at 500 Hz and 1000 Hz.

Correlation of air-bone gap and size of Enlarged Vestibular Aqueduct in children

OBJECTIVE

Enlarged vestibular aqueduct (EVA) is an inner ear malformation that represents an important cause of pediatric hearing loss. While certain elements in the history or audiogram may suggest EVA, it is most often diagnosed using computed tomography (CT). The present investigation was conducted to determine if the size of the audiometric air-bone gap (ABG) is correlated with the size of the vestibular aqueduct in the pediatric population using three vestibular aqueduct measurements. These included the fundus, midpoint, and porous widths of the vestibular aqueduct.

STUDY DESIGN

This is a retrospective cohort study.

SETTING

This study took place at a tertiary care referral center.

PATIENTS

Fifty-five children (33 female; 22 male) with a confirmed diagnosis of unilateral or bilateral EVA as determined by prior imaging of the inner ear were included in the study.

MAIN OUTCOME MEASURES

Associations of EVA measurements with ABGs at 0.5 and 1 kHz were evaluated using Pearson correlation coefficients.

RESULTS

All of the correlation coefficients were positive, indicating that as EVA measurements increased so did the ABG. Only the correlation between fundus width and ABG at 1 kHz was not statistically significant.

CONCLUSIONS

ABGs measured during audiometric testing correlate with the size of the EVA and ABGs can be clinical predictors of the severity of the bony abnormality. These data support the third window theory of conductive hearing loss in pediatric EVA.

Morphology and cochlear implantation in enlarged vestibular aqueduct

PURPOSE

The purpose of this work is to explore audiometry following cochlear implantation (CI) in patients with enlarged vestibular aqueduct (EVA) and to investigate the effects of inner ear morphological variation on post CI audiometry.

METHODS

This was a retrospective review of both natural and cochlear-implant-aided audiometry results, using all available measurements in a mixed-effects model accounting for longitudinal change and the grouping structure of ears. Patients who visited our tertiary academic medical center between 2000 and 2016 were identified as having EVA according to Cincinnati criteria on radiological examination; patients eligible for CI were then selected for analysis.

RESULTS

Multivariable modeling showed a statistically significant hearing improvement in ears with EVA undergoing CI with regards to pure tone average (-64.0 dB, p < 0.0001), speech reception threshold (-57.90 dB, p < 0.0001), and word score (34.8%, p > 0.0001). Vestibular aqueduct midpoint size and the presence of incomplete partition type II (IP II) did not have significant independent associations with audiometric findings. However, multivariable modeling revealed a statistically significant interaction between IP II and CI such that IP II ears demonstrated a decrease in WS improvement of 30.2% (p = 0.0059) compared to non-IP II ears receiving CI.

CONCLUSION

There is a statistically significant audiometric benefit to ears with EVA receiving CI. Morphology, specifically the presence of IP II, may hinder CI benefit in terms of word score however this finding needs clinical validation. This data improves personalization of surgical counseling and planning for patients with EVA considering CI.

Hearing loss in enlarged vestibular aqueduct and incomplete partition type II

PURPOSE

The purpose of this work is to identify the role of incomplete partition type II on hearing loss among patients with enlarged vestibular aqueduct (EVA).

BACKGROUND

EVA is a common congenital inner ear malformation among children with hearing loss, where vestibular aqueduct morphology in this population has been shown to correlate to hearing loss. However, the impact of incomplete partition between cochlear turns on hearing loss has not been, despite meaningful implications for EVA pathophysiology.

METHODS

A retrospective review of radiology reports for patients who had computed tomography (CT) scans with diagnoses of hearing loss at a tertiary medical center between January 2000 and June 2016 were screened for EVA. CT scans of the internal auditory canal (IAC) for those patients with EVA were examined for evidence of incomplete partition type II (IP-II), measurements of midpoint width and operculum width a second time, and patients meeting Cincinnati criteria for EVA selected for analysis. Statistical analysis including chi-square, Wilcoxon rank-sum, and t-tests were used to identify differences in outcomes and clinical predictors, as appropriate for the distribution of the data. Linear mixed models of hearing test results for all available tests were constructed, both univariable and adjusting for vestibular aqueduct morphometric features, with ear-specific intercepts and slopes over time.

RESULTS

There were no statistically significant differences in any hearing test results or vestibular aqueduct midpoint and operculum widths. Linear mixed models, both univariable and those adjusting for midpoint and operculum widths, did not indicate a statistically significant effect of incomplete partition type II on hearing test results.

CONCLUSIONS

Hearing loss due to enlarged vestibular aqueduct does not appear to be affected by the presence of incomplete partition type II. Our results suggest that the pathophysiological processes underlying hearing loss in enlarged vestibular aqueduct may not be a result of cochlear malformation, and instead are more likely to involve vestibular aqueduct or cellular and molecular-level mechanisms of hearing loss.

Spectrum of Third Window Abnormalities: Semicircular Canal Dehiscence and Beyond

Third window abnormalities are defects in the integrity of the bony structure of the inner ear, classically producing sound-/pressure-induced vertigo (Tullio and Hennebert signs) and/or a low-frequency air-bone gap by audiometry. Specific anatomic defects include semicircular canal dehiscence, perilabyrinthine fistula, enlarged vestibular aqueduct, dehiscence of the scala vestibuli side of the cochlea, X-linked stapes gusher, and bone dyscrasias. We discuss these various entities and provide key examples from our institutional teaching file with a discussion of symptomatology, temporal bone CT, audiometry, and vestibular-evoked myogenic potentials.

The large vestibular aqueduct: A new definition based on audiologic and computed tomography correlation

Objective

The study goal was to determine the prevalence and clinical significance of a large vestibular aqueduct (LVA) in children with sensorineural hearing loss (SNHL).

Study Design and Setting

We conducted a retrospective review of a pediatric SNHL database. One hundred seven children with SNHL were selected and their radiographic and audiometric studies were evaluated. Radiographic comparisons were made to a group of children without SNHL.

Results

A vestibular aqueduct (VA) larger than the 95th percentile of controls was present in 32% of children with SNHL. Progressive SNHL was more likely to occur in ears with an LVA and the rate of progressive hearing loss was greater than in ears without an LVA. The risk of progressive SNHL increased with increasing VA size as determined by logistic regression analysis.

Conclusions

An LVA is defined as one that is ≥2mm at the operculum and/or ≥1 mm at the midpoint in children with nonsyndromic SNHL. An LVA appears to be more common than previously reported in children with SNHL. A linear relationship is observed between VA width and progressive SNHL.

Significance

The finding of an LVA in children with SNHL provides diagnostic as well as prognostic information. © 2007 American Academy of Otolaryngology-Head and Neck Surgery Foundation. All rights reserved.

Pattern of hearing loss following cochlear implantation

Cochlear implantation is associated with deterioration in hearing. Despite the fact that the damage is presumed to be of sensory origin, residual hearing is usually assessed by air-conduction thresholds alone. This study sought to determine if surgery may cause changes in air- and bone-conduction thresholds producing a mixed-type hearing loss. The sample included 18 patients (mean age 37 years) with an air-bone gap of 10 dB over three consecutive frequencies and measurable masked and reliable bone-conduction thresholds of operated and non-operated ears who underwent cochlear implant surgery. All underwent comprehensive audiologic and otologic assessment and imaging before and after surgery. The air-bone gap in the treated ears was 17-41 dB preoperatively and 13-59 dB postoperatively over 250-4,000 Hz. Air-conduction thresholds in the treated ears significantly deteriorated after surgery, by a mean of 10-21 dB. Bone-conduction levels deteriorated nonsignificantly by 0.8-7.5 dB. The findings indicate that the increase in air-conduction threshold after cochlear implantation accounts for most of the postoperative increase in the air-bone gap. Changes in the mechanics of the inner ear may play an important role. Further studies in larger samples including objective measures of inner ear mechanics may add information on the source of the air-bone gap.

Coronal CT scan measurements and hearing evolution in enlarged vestibular aqueduct syndrome

OBJECTIVE

To assess the correlation between the enlarged vestibular aqueduct (EVA) diameter and (1) the hearing loss level (mild, moderate, severe and profound and (2) the hearing evolution. The secondary objective was to obtain measurement limits on the coronal plane of the temporal bone CT scan for the diagnosis of EVA.

METHODS

Retrospective study in a tertiary pediatric center. Mastoid CT scans were reviewed to measure the VA diameter at its midpoint and operculum on axial and coronal planes in a pathologic and normal population. We used their serial audiograms to assess the evolution of hearing.

RESULTS

101 EVA was identified out of 1812 temporal bones CT scan from our radiologic database in 8 years. Bone conduction was stable after a mean follow-up of 40.9 ± 32.9 months. PTA has been the most affected in time by the EVA (p=0.006). No correlation was identified between impedancemetry and the diameter of the EVA. On the diagnostic audiogram, 61% of hearing loss were in the mild and moderate hearing levels; at the end of the follow-up 64% of hearing loss are still in the mild and moderate hearing levels. The cut-off values for the coronal midpoint and operculum planes on the CT scan to diagnose an EVA are 2.4 mm and 4.34 mm respectively.

CONCLUSIONS

Conductive or mixed hearing loss might be the first manifestation of EVA. Coronal CT scan cuts can provide additional information to evaluate EVA especially when axial cuts are not conclusive.

Third windows as a cause of failure in hearing gain after exploratory tympanotomy

OBJECTIVE

Exploratory tympanotomy (ET) can be performed selectively on patients who have air-bone gaps (ABGs) without any apparent external or middle ear abnormalities for diagnosis and treatment of their conductive hearing loss. However, surgeons cannot always find middle ear problems. It has recently been reported that pathologic third windows in inner ears can cause ABGs. Therefore, the authors conducted this study to evaluate the inner ear anatomical problems of patients who had undergone ET.

STUDY DESIGN

Case series with chart review.

SETTING

Tertiary center.

SUBJECTS AND METHODS

The authors included 51 consecutive patients with ABGs ≥20 dB who had undergone ET at Yonsei University Severance Hospital between 2005 and 2009. In the preoperative evaluations, all 51 patients showed normal drums on otoscopy, and no abnormal middle ear problems that could cause ABGs were detected on temporal bone computed tomography (TBCT). The authors retrospectively reevaluated the hearing results and the causes of their conductive hearing loss, including the inner ear problems, through a review of their TBCT.

RESULTS

Six of the 51 patients were found to have inner ear abnormalities with possible pathologic third windows. Four had enlarged vestibular aqueducts (EVAs), and 2 had superior semicircular canal dehiscence (SSCD). All patients with pathologic third windows failed to improve their hearing.

CONCLUSION

About 12% of the patients had inner ear anomalies, which could possibly cause ABGs. Inner ear conductive components might lead to frustrating results. Therefore, surgeons must take inner ear conductive components into account before attempting ET in patients with inner ear anomalies.

The prevalence of superior canal dehiscence syndrome as assessed by temporal bone computed tomography imaging

CONCLUSION

When a diagnosis of superior canal dehiscence syndrome (SCDS) was made based solely on CT scans, 80% of cases assessed were false positive. This stresses the importance of diagnosing SCDS on the basis of both CT findings and clinical symptoms.

OBJECTIVES

All the coronal computed tomography (CT) scans of the temporal bones retained in this clinic were reviewed to determine how many of these examined ears have dehiscence(s) of the superior semicircular canal (SSCC). We also determined how many of the ears with a dehiscence of SSCC could also be diagnosed clinically on CT scans as having SCDS.

METHODS

CT scans of 82 patients, covering 164 ears, were reviewed to determine how many of these ears had dehiscence of SSCC. Of the ears found to have a dehiscence of SSCC in the above procedure, it was determined how many ears could also be diagnosed clinically as having SCDS.

RESULTS

Dehiscence of SSCC was demonstrated in 5 (3%) of the 164 ears assessed. Of the five ears noted to have a dehiscence of SSCC, the condition was also considered clinically to be SCDS in only one ear (0.6%).

Communication routes between intracranial spaces and inner ear: function, pathophysiologic importance and relations with inner ear diseases

OBJECTIVE

There exist 3 communication routes between the intracranial space and the inner ear, the vestibular aqueduct, the cochlear aqueduct, and the internal auditory canal. They possess a key role in inner ear pressure regulation and fluid homeostasis and are related to inner ear diseases.

REVIEW METHODS

Relevant literature was reviewed, and the current knowledge of the anatomy, physiologic importance, and relations to inner ear diseases were described. Pathologic communication routes such as semicircular canal dehiscence syndrome were highlighted as well.

CONCLUSION

Abnormalities in all 3 communication routes may predispose or be the cause of distinct inner ear pathologic condition and involved in other cochlear and vestibular syndromes, in which their role is not completely clear. The increasing knowledge of the underlying mechanisms encourages promising approaches for possible intervention in the future.

Delineating the hearing loss in children with enlarged vestibular aqueduct. Laryngoscope. 2008;118:2062-2066. [PMID: 18665003 DOI: 10.1097/mlg.0b013e31818208ad]

OBJECTIVE/HYPOTHESIS

To explore the clinical characteristics and audiologic outcomes in children with enlarged vestibular aqueduct (EVA).

STUDY DESIGN

Retrospective study in a pediatric tertiary care facility.

METHODS

A total of 54 cases (82 ears) of children with EVA were identified with complete records, including otologic evaluation, imaging studies, and audiologic assessments. The diagnosis of EVA was confirmed by computerized tomography scan/magnetic resonance imaging of the temporal bone. Hearing status was assessed using behavioral testing or auditory brainstem response (ABR). Tympanometry, acoustic reflex, and vestibular evoked myogenic potential (VEMP) testing were also performed when appropriate.

RESULTS

Fifty-two percent of our EVA cases showed bilateral involvement, and 43% of all ears with EVA also had cochlear malformations, such as Mondini dysplasia. Sensorineural HL was initially diagnosed in 16 ears (20% of the total) with EVA whereas conductive or mixed HL was found in 66 ears (80% of the total). Further review of all EVA cases with sensorineural HL showed lack of proper bone conduction testing, so air-bone gaps were missed. Despite air-bone gaps in EVA ears, middle ear pressure and mobility were usually normal, along with present acoustic reflexes. VEMP responses were present with abnormally low thresholds.

CONCLUSIONS

Air-bone gap(s) can be found in most ears with EVA if both air and bone conduction thresholds are properly tested. Normal tympanometry, presence of acoustic reflex and low threshold VEMP responses suggest that the air-bone gap in EVA is due to an inner ear anomaly, similar to the "third" labyrinthine window syndrome.

Clinical investigation and mechanism of air-bone gaps in large vestibular aqueduct syndrome

OBJECTIVES

Patients with large vestibular aqueduct syndrome (LVAS) often demonstrate an air-bone gap at the low frequencies on audiometric testing. The mechanism causing such a gap has not been well elucidated. We investigated middle ear sound transmission in patients with LVAS, and present a hypothesis to explain the air-bone gap.

METHODS

Observations were made on 8 ears from 5 individuals with LVAS. The diagnosis of LVAS was made by computed tomography in all cases. Investigations included standard audiometry and measurements of umbo velocity by laser Doppler vibrometry (LDV) in all cases, as well as tympanometry, acoustic reflex testing, vestibular evoked myogenic potential (VEMP) testing, distortion product otoacoustic emission (DPOAE) testing, and middle ear exploration in some ears.

RESULTS

One ear with LVAS had anacusis. The other 7 ears demonstrated air-bone gaps at the low frequencies, with mean gaps of 51 dB at 250 Hz, 31 dB at 500 Hz, and 12 dB at 1,000 Hz. In these 7 ears with air-bone gaps, LDV showed the umbo velocity to be normal or high normal in all 7; tympanometry was normal in all 6 ears tested; acoustic reflexes were present in 3 of the 4 ears tested; VEMP responses were present in all 3 ears tested; DPOAEs were present in 1 of the 2 ears tested, and exploratory tympanotomy in 1 case showed a normal middle ear. The above data suggest that an air-bone gap in LVAS is not due to disease in the middle ear. The data are consistent with the hypothesis that a large vestibular aqueduct introduces a third mobile window into the inner ear, which can produce an air-bone gap by 1) shunting air-conducted sound away from the cochlea, thus elevating air conduction thresholds, and 2) increasing the difference in impedance between the scala vestibuli side and the scala tympani side of the cochlear partition during bone conduction testing, thus improving thresholds for bone-conducted sound.

CONCLUSIONS

We conclude that LVAS can present with an air-bone gap that can mimic middle ear disease. Diagnostic testing using acoustic reflexes, VEMPs, DPOAEs, and LDV can help to identify a non-middle ear source for such a gap, thereby avoiding negative middle ear exploration. A large vestibular aqueduct may act as a third mobile window in the inner ear, resulting in an air-bone gap at low frequencies.

A mechano-acoustic model of the effect of superior canal dehiscence on hearing in chinchilla

Superior canal dehiscence (SCD) is a pathological condition of the ear that can cause a conductive hearing loss. The effect of SCD (a hole in the bony wall of the superior semicircular canal) on chinchilla middle- and inner-ear mechanics is analyzed with a circuit model of the dehiscence. The model is used to predict the effect of dehiscence on auditory sensitivity and mechanics. These predictions are compared to previously published measurements of dehiscence related changes in chinchilla cochlear potential, middle-ear input admittance and stapes velocity. The comparisons show that the model predictions are both qualitatively and quantitatively similar to the physiological results for frequencies where physiologic data are available. The similarity supports the third-window hypothesis of the effect of superior canal dehiscence on auditory sensitivity and mechanics and provides the groundwork for the development of a model that predicts the effect of superior canal dehiscence syndrome on auditory sensitivity and mechanics in humans.

The large vestibular aqueduct--case report and review of the literature

Patients with a large vestibular aqueduct (LVA) suffer from a loss of hearing in childhood at an early onset. An acute loss of hearing can be precipitated by minor head trauma. Until now there seems to be no sufficient therapy for stopping the progression of a loss of hearing. It has been shown that a cochlear implantation is a worthwhile procedure if the patient is almost deaf. We report the case of a patient with a bilateral LVA. A loss of hearing was confirmed at the age of 16 months. Exposure to loud noise triggered an acute progression of the hearing loss. At the age of 18 years, LVA was confirmed radiologically, revealing an enlarged endolymphatic duct and sac in MRI scans and an enlarged vestibular aqueduct in the CT scan. We successfully performed a cochlear implant (MED-EL, Combi 40+ flex). Proceeding from this case report, the paper reviews the literature on LVA.