Large vestibular aqueduct syndrome and stapes fixation

Third window lesions of the inner ear: A pictorial review

PURPOSE

Radiographic review of pathologies that associate with third window syndrome.

METHODS

Case series and literature review.

RESULTS

Eight unique third window conditions are described and illustrated, including superior, lateral, and posterior semicircular canal dehiscence; carotid-cochlear, facial-cochlear, and internal auditory canal-cochlear dehiscence, labyrinthine erosion from endolymphatic sac tumor, and enlarged vestibular aqueduct.

CONCLUSION

The present study highlights the characteristic imaging features and symptoms to differentiate third window pathologies for expedient diagnosis and management planning.

A Large Vestibular Aqueduct With Conductive Hearing Loss as the Only Manifestation

Conductive hearing loss is a common clinical condition caused by disorders of the middle and external ear. Here, we report a case of conductive hearing loss with complete tympanic membranes. Clinical examinations revealed no external and middle ear lesions, but high-resolution temporal bone computed tomography revealed enlarged vestibular aqueducts. Detailed audiological tests and follow-up results indicate that the exclusive air-bone gap is the outcome of inner ear malformation but not middle ear lesions, preventing the need for tympanic assessment.

Prevalence of occult cochlear basal turn patency

BACKGROUND

Perilymph gusher (PLG) is a rare complication of otologic surgery attributed to a communication between the cochlea and the internal auditory canal (IAC). Subtle patency between the cochlear basal turn and IAC has recently been identified on computed tomography (CT) as a risk factor, specifically when the defect is > 0.75 mm.

OBJECTIVES

Investigate the prevalence of radiographic cochlear basal turn patency.

MATERIALS AND METHODS

Patients with CT of the temporal bones and inner ears interpreted as "normal" were included. An otologist and a radiologist independently reviewed CTs to measure radiographic dehiscence in an oblique plane along the interface of the cochlea and IAC. Known PLGs were excluded.

RESULTS

Two hundred and ten ears were included (88 conductive or mixed hearing loss, 62 sensorineural hearing loss, 41 audiometrically normal ears). 71 ears (33.8%) were radiographically patent. Mean defect width was 0.41 mm (0.15-0.7 mm). Defect width was not associated with type of hearing loss, age, or gender. No defects were wider than 0.75 mm.

CONCLUSIONS

Radiographic patency of the cochlear basal turn may be present in patients with hearing loss and normal hearing, but patency > 0.75 mm (i.e. risk for PLG) is rare.

Gusher in stapes surgery: a systematic review

OBJECTIVE

The aim of this study is to perform a systematic literature review on the occurrence of gusher during stapes surgery, to understand its surgical management and outcomes.

METHODS

The PRISMA standard was applied to identify English, Italian or French-language studies, related to stapes surgery and mentioning gusher or perilymphatic leak. Full-texts lacking information on the management of gusher and/or the post-operative hearing outcome were excluded.

RESULTS

Twenty-four articles were eventually included. Seventy-six patients were involved in the qualitative synthesis. The management of gusher mostly consisted in covering the oval window and/or filling the tympanic cavity, with absorbable and autologous graft materials. Packing of the external auditory canal was reported in 51 patients (67%). Gusher was related to complete/profound loss of hearing in 25% of the cases and to a worsening of hearing function in 31% of patients. In 19% of patients an improvement in hearing tests was reported; in 28% the hearing function was unchanged. Post-operative vestibular symptoms were reported in 7 patients, and were mainly mild and transient. The absence of vestibular symptoms was underlined in 9 cases, while in 79% of the patients the authors did not provide information.

CONCLUSION

The unexpected occurrence of gusher during stapes surgery represents a relevant issue for the otologic surgeon. Its management most commonly consists in plugging the oval window and the tympanic cavity. In most of the cases, a stapes prosthesis could be positioned. The results on hearing and vestibular functions are widely variable.

Large vestibular aqueduct syndrome and endolymphatic hydrops: two presentations of a common primary inner-ear dysfunction?

Objective:

To present the theory that large vestibular aqueduct syndrome (i.e. the recognised existence of an enlarged vestibular aqueduct with progressive sensorineural hearing loss) and endolymphatic hydrops are due to a common primary dysfunction of inner-ear fluid homeostasis.

Method:

Case report and review of the world literature concerning large vestibular aqueduct syndrome and endolymphatic hydrops.

Results:

We report a family in which one sibling suffered from large vestibular aqueduct syndrome while the other had classic Ménière's disease. This suggests that large vestibular aqueduct syndrome and endolymphatic hydrops, in some cases, may be due to a common primary dysfunction of inner-ear fluid homeostasis.

Conclusion:

To our knowledge, this is the first report in the world literature to postulate that variation in the relative compliance of inner-ear membranes could be the factor that determines the manifestation of the disorder as either endolymphatic hydrops or large vestibular aqueduct syndrome.

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.

Acoustic Reflex Screening of Conductive Hearing Loss for Third Window Disorders

Objective

This study examines the effectiveness of acoustic reflexes in screening for third window disorders (eg, superior semicircular canal dehiscence) prior to middle ear exploration for conductive hearing loss.

Study Design

Case series with chart review.

Setting

Outpatient tertiary otology center.

Subjects and Methods

A review was performed of 212 ears with acoustic reflexes, performed as part of the evaluation of conductive hearing loss in patients without evidence of chronic otitis media. The etiology of hearing loss was determined from intraoperative findings and computed tomography imaging. The relationship between acoustic reflexes and conductive hearing loss etiology was assessed.

Results

Eighty-eight percent of ears (166 of 189) demonstrating absence of all acoustic reflexes had an ossicular etiology of conductive hearing loss. Fifty-two percent of ears (12 of 23) with at least 1 detectable acoustic reflex had a nonossicular etiology. The positive and negative predictive values for an ossicular etiology were 89% and 57% when acoustic reflexes were used alone for screening, 89% and 39% when third window symptoms were used alone, and 94% and 71% when reflexes and symptoms were used together, respectively.

Conclusion

Acoustic reflex testing is an effective means of screening for third window disorders in patients with a conductive hearing loss. Questioning for third window symptoms should complement screening. The detection of even 1 acoustic reflex or third window symptom (regardless of reflex status) should prompt further workup prior to middle ear exploration.

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.

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

The Bing test is based on the principle that occlusion of the external auditory meatus improves the perception of bone-conducted sounds unless there is a conductive hearing impairment. An air-bone gap has been reported in patients with large vestibular aqueduct (LVA) syndrome without apparent middle ear dysfunction. We therefore performed the Bing test on nine patients with this syndrome to evaluate whether it is associated with an air-bone gap or middle ear dysfunction. Bone conduction thresholds did not change significantly during the Bing test in any patient. Because an air-bone gap is observed in patients with abnormal communication between the inner ear and cerebrospinal fluid through the LVA, dehiscent superior canal, or dilated inner ear meatus; we propose that a 'three windows' model (in which the abnormal communication provided by the enlarged endolymphatic duct and sac in LVA acts as the 'third window' for sound conductance) might explain the air-bone gap in such patients.

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.

Large vestibular aqueduct syndrome: a human temporal bone study

OBJECTIVES/HYPOTHESIS

Large vestibular aqueduct syndrome (LVAS) is one of the common causes of hearing loss (HL). All prior studies have reported some anomalies associated with LVAS by imaging techniques. This study was undertaken to determine prevalence of LVAS in our temporal bone (TB) collection and its relationship to other systemic or otologic anomalies.

STUDY DESIGN

Retrospective, TB histopathologic study.

METHODS

Anteroposterior diameters of internal (IA) and external (EA) apertures were measured in 40 normal TBs (40 cases). TBs were considered as large vestibular aqueduct (LVA) if width of apertures was 95% greater than "normals." Systemic and otologic anomalies and histopathology of ears with LVAS were noted.

RESULT

Of 1,608 non-"normal" TBs, 63 had LVA. There was negative correlation between IA and EA in 48 TBs with only enlarged IA. Fifteen TBs with enlarged EA always had enlarged IA and were therefore considered as LVAS. The most common pathologic condition was congenital heart anomaly. The most common syndrome or dysplasia was Mondini's. The most common anomalies of external and middle ears were dehiscent facial nerves, low set auricles, and ossicular deformities. Inner ear anomalies included modiolar deficiencies, hair cell loss, interscalar septum defects, and strial atrophy. There was no record of family history of HL, head injury, or craniofacial, branchial, or thyroidal abnormalities.

CONCLUSION

Because HL associated with LVAS may be attributed to other ear anomalies, it is important to investigate other inner ear problems and system diagnoses that may indicate a syndrome in patients with radiologically diagnosed LVAS.

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.

Enlarged vestibular aqueduct syndrome in the pediatric population

OBJECTIVE

To correlate clinical and audiometric findings with the radiologic appearance in patients with enlarged vestibular aqueduct.DESIGN A retrospective review of data from enlarged vestibular aqueduct patients identified in a pediatric hearing-impaired database of 1,200 patients. SETTING A tertiary care pediatric referral center.

PATIENTS

Subjects were included for study with a radiographic diagnosis of enlarged vestibular aqueducts in at least one ear by a pediatric neuroradiologist.

MAIN OUTCOME MEASURES

Audiometric evaluations and radiographic temporal bone measurements.

RESULTS

Seventy-seven patients were identified with an enlarged vestibular aqueduct with a male-to-female ratio of 1:1.5. Patients were followed for a mean of 34 months (range, 0-179 months). Hearing loss was bilateral in 87% of cases. Vestibular symptoms were present in only three (4%) of the patients. Three patients (4%) suffered a sudden decrease in hearing after mild head trauma. Borderline enlargement of the vestibular aqueduct was associated with varying degrees of sensorineural hearing loss. Ninety-seven percent (64 of 66) of ears in control subjects with no sensorineural hearing loss had normal vestibular aqueduct measurements at the midpoint and operculum. Overall, the audiogram remained stable in 51% of ears, fluctuated in 28%, and progressively worsened in 21%. Measurements of the vestibular aqueduct at the midpoint and the operculum did not correlate with the audiometric threshold or the audiogram configuration. However, mean vestibular aqueduct size at the operculum was significantly larger in those with a progressive loss when compared with those with a fluctuating or stable hearing outcome.

CONCLUSIONS

Overall, audiometric thresholds remained generally stable, with sudden deterioration of hearing after head trauma seen in only three male patients. Progression of hearing loss after head trauma was not a significant finding in our patient population. Vestibular aqueduct opercular size alone showed a direct correlation with the audiometric outcome. Borderline enlarged vestibular aqueduct measurements appear to be associated with sensorineural hearing loss.

Use of laboratory evaluation and radiologic imaging in the diagnostic evaluation of children with sensorineural hearing loss

OBJECTIVE

Laboratory testing and radiologic imaging are commonly used to delineate syndromic from nonsyndromic sensorineural HL (SNHL). The aim of this study was to examine the yield of laboratory tests and radiologic imaging commonly used in the diagnostic evaluation of SNHL in children.

STUDY DESIGN

Retrospective analysis of 114 (54 female, 60 male) consecutively investigated children with SNHL between 1998 and 2000 at a tertiary-care university hospital.

METHODS

Results of routine laboratory testing to assess autoimmunity, blood dyscrasias, endocrine abnormalities, renal function, infection, and cardiac testing were reviewed. Results of radiologic evaluation were also reviewed. In general, computed tomography (CT) was obtained in patients with symmetric SNHL, whereas magnetic resonance imaging (MRI) with or without CT was obtained in asymmetric SNHL.

RESULTS

Laboratory evaluation of the blood did not yield the etiology of SNHL in any patient. Blood tests for autoimmune disease were often positive but did not correlate with clinical disease. Nonspecific elevation of erythrocyte sedimentation rate (ESR) and antinuclear antibody (ANA) was present in 22% of cases. An abnormal electrocardiogram with a prolonged QT interval resulted in the diagnosis of Jervall and Lange-Nielsen syndrome. In the 97 patients who underwent radiologic studies, abnormalities were present in 38 of 97 studies (39%). Isolated inner ear malformations were twice as common as multiple abnormalities with large vestibular aqueducts as the most common isolated finding.

CONCLUSION

In the evaluation of children with unexplained SNHL, routine laboratory evaluation should be reconsidered given its low diagnostic yield. However, radiologic abnormalities of the inner ear are common. Identification of inner ear malformations has direct impact on management of these children, suggesting that all children should undergo radiologic imaging as an integral component of evaluation of SNHL.