The large vestibular aqueduct syndrome in children. A review of 12 cases and the description of a new clinical entity

Congenital malformations of the inner ear and the vestibulocochlear nerve in children with sensorineural hearing loss: evaluation with CT and MRI

PURPOSE

The purpose of this work was to study the diagnostic value of CT and MRI in children with sensorineural hearing loss and to analyze anatomic abnormalities of the inner ear and the vestibulocochlear nerve in this patient group.

METHOD

We evaluated 42 inner ears in 21 children with congenital deafness who had congenital inner ear malformations and who were candidates for cochlear implants. All patients were studied with high resolution MR and helical CT examinations. The MR study included a T2-weighted 3D fast SE sequence. We describe and tabulate the anatomic abnormalities. Special attention was given to abnormalities of the vestibulocochlear nerve. The field of view in the plane according to the length axis of the internal auditory canal (IAC) was 4 cm. Additional continuous parasagittal reformations perpendicular to the length axis of the IAC were studied with a field of view of 3 cm.

RESULTS

CT and MRI allowed accurate identification of malformations of the inner ear in children with congenital deafness. We identified 99 malformations, with a majority of patients demonstrating multiple abnormalities. Common imaging findings were Mondini abnormality and Mondini variants (12/42) and fusion of the lateral or superior semicircular canal with the vestibule (12/42). MRI demonstrated in 9 of 21 patients a rudimentary or absent vestibulocochlear nerve in the auditory canal.

CONCLUSION

CT and MRI are important modalities to analyze the inner ear in children who are candidates for cochlear implants. MRI with an extremely small field of view should be used to study possible abnormalities of the vestibulocochlear nerves. This may alter clinical care and allow cochlear implant placement in patients whose electrodiagnostic studies suggest that the implant should not be performed. The detailed analysis of abnormalities of the inner ear might establish prognostic factors.

Progressive fluctuant hearing loss, enlarged vestibular aqueduct, and cochlear hypoplasia in branchio-oto-renal syndrome

OBJECTIVE

To study the results of petrosal bone imaging and audiometric long-term follow-up of two patients with branchio-oto-renal (BOR) syndrome and relate them to the clinical features, including caloric responses.

STUDY DESIGN

Longitudinal case study.

SETTING

Tertiary referral center.

PATIENTS

A father and son with the BOR syndrome.

MAIN OUTCOME MEASURES

Both patients underwent imaging studies to detect and evaluate inner ear anomalies. Longitudinal audiometric analysis of the hearing threshold data over the previous 23 years was performed. Caloric tests were performed at various ages.

RESULTS

The son had a short, wide internal acoustic canal, a hypoplastic cochlea, a plump vestibule, and a wide vestibular aqueduct on both sides; the semicircular canals and endolymphatic sac were of normal size. He showed progressive fluctuant sensorineural hearing loss. Caloric tests disclosed hyporeflexia on the left side. The father had a plump internal acoustic canal and hypoplastic cochlea on both sides. The left vestibule was hypoplastic, and the left vestibular aqueduct was marginally enlarged. He showed severe hearing impairment, without substantial progression or fluctuation, and caloric areflexia on the left side.

CONCLUSION

These findings suggest a correlation between progressive fluctuant sensorineural hearing loss with caloric hypofunction and the presence of an enlarged vestibular aqueduct in the BOR syndrome. Additional longitudinal case studies are needed to further evaluate such a correlation.

Cochlear implantation in children with large vestibular aqueduct syndrome and a review of the syndrome

OBJECTIVE

Children with Large Vestibular Aqueduct Syndrome (LVAS) frequently develop speech and language skills prior to deterioration of their hearing. Operations designed to halt the progression of hearing loss have largely failed so the question of Cochlear Implantation in these children has arisen. It had been suggested that there would be technical difficulties in implanting these patients and, therefore, there had been an initial reluctance to proceed to implantation. The aim of the present paper is to assess surgical and functional outcomes in implanted children with LVAS and review the related literature.

MATERIAL AND METHODS

From the 170 children assessed by MRI in the Nottingham Paediatric Cochlear Implant Programme, seven (4%) were identified as having LVAS. Four of these children were implanted and had at least 12 months follow up. Two of the children are on the waiting list for implantation and one child was not implanted because of absence of the cochlear nerve. Operative findings, complications and outcome measures were recorded. The auditory skills of the children were assessed before implantation and 1 year following implantation. A literature search was done to identify other series with experience in implanting children with LVAS.

RESULTS

Full insertion of the electrode array was achieved in all our cases. After cochleostomy two patients experienced a mild CSF leak that was easily controlled by the muscle graft. On the first day post-operation two patients were nauseous and one had an episode of vomiting, however, all were discharged within 24 h of surgery. Initial outcome measures at 12 months post-implantation were encouraging showing significant progress in children's auditory skills.

CONCLUSIONS

The results of the present study and the review of the literature suggest that LVAS is not a contraindication to implantation as initial concerns about severe perilymph leaks and surgical complications have proved to be unfounded. The post-operative progress of these children in listening skills also suggest that these children are suitable for cochlear implantation

Familial enlarged vestibular aqueduct syndrome

Enlarged vestibular aqueduct syndrome is a clinical disease entity associated with anatomic abnormality of the bony canal in the temporal bone containing the endolymphatic duct and sac. The definition of this syndrome is progressive sensorineural hearing loss with an isolated enlarged vestibular aqueduct. Familial inheritance of enlarged vestibular aqueduct syndrome is rare, and the correct mode of inheritance has not been discovered. This report is the study of familial inheritance with enlarged vestibular aqueduct syndrome. Clinical audiological, radiographic, and chromosomal analyses were performed in this case, which reports on two female probands who are offspring of normal parents. According to the study of pedigree, familial inheritance of enlarged vestibular aqueduct syndrome is strongly suspected as an autosomal recessive trait. Further study should be focused on discovering the genetic evaluation of familial inheritance of enlarged vestibular aqueduct syndrome.

Imaging evaluation of sensorineural hearing loss

The imaging evaluation of patients with sensorineural hearing loss (SNHL) focuses on the acoustic pathways from the cochlea to the auditory cortex. Magnetic resonance imaging (MRI) is the modality of choice for most patients with SNHL, though computed tomography (CT) also plays an important role in the evaluation of bony changes and in patients for whom MRI is contraindicated. Conventional enhanced MRI is the most commonly used technique in this clinical setting. High-resolution fast spin-echo T2 MRI is an adjunctive technique that provides exquisite evaluation of the cerebellopontine angle (CPA), internal auditory canal (IAC), cranial nerves, and membranous labyrinth, and plays a significant role in the diagnosis and surgical evaluation of SNHL. Categories of lesions that cause SNHL include brain lesions involving central auditory pathways; neoplasms of the CPA and IAC, the most common being schwannoma; other neoplastic, congenital, and cystic masses of the CPA and IAC; congenital anomalies of the inner ear; intrinsic cochlear nerve defects, inflammatory processes of the inner ear; and temporal bone trauma.

Isolated large vestibular aqueduct syndrome in a family

This paper presents the second case in the literature of large vestibular aqueduct syndrome without associated cochlear anomalies in 2 members of the same family. The syndrome is frequently associated with sensorineural hearing loss presenting in childhood. The onset is commonly sudden, following an event causing increased intracranial pressure. On the basis of an emerging pattern of inheritance, we recommend screening siblings of an affected child. We also discuss the importance of characterizing the extent of disease of the inner ear.

Audiological findings in large vestibular aqueduct syndrome

An enlarged vestibular aqueduct is a congenital disorder causing early onset and progressive hearing loss in children. This paper presents the audiological findings at first presentation and the audiological evolution in 10 consecutive cases presenting with hearing loss and showing a large vestibular aqueduct on imaging. The reported onset of the hearing loss is within the first few years of life. Most of the cases (80%) showed bilateral involvement. The sex ratio was 1. Patients presented on average at age 5 with a median hearing loss of 62 dB at the speech frequencies. The hearing loss was essentially asymmetrical with an interaural difference, of 33 dB and it was a mixed type of hearing loss in 90% of the cases. The authors claim that the conductive component of this hearing loss is a pure cochlear conductive loss which may be pathognomonic for the disease. The presence of a conductive component in a child is easily misinterpreted as a middle ear ventilation problem or in case of good ventilation as an ossicular problem (type otosclerosis). In addition and in contrast to most literature data, the authors did not find evidence for stabilization of the hearing loss but they found a steady decrease of the hearing at an average rate of 4 dB/year.

Vestibular disturbance in patients with large vestibular aqueduct syndrome (LVAS)

Large vestibular aqueduct syndrome (LVAS) is a common inner ear anomaly responsible for some unusual vestibular and audiological symptoms. The gross appearance of CT scan of the inner ear is generally normal. However, precise measurement of the inner ear components reveals abnormal dimensions, which may account for accompanying auditory or vestibular dysfunction. It has been reported that sudden increase in cerebrospinal fluid pressure can cause further deterioration of hearing due to transmission of pressure to the inner ear through the enlarged vestibular aqueduct. However, vestibular function is not often studied. In this report, audiovestibular function of 10 patients with large vestibular aqueducts was analysed and compared with the severity of the radiological deformity. The literature was reviewed and typical findings were discussed to emphasize varying aspects of audiovestibular function. It was found that some patients with LVAS have some spontaneous or provoked vestibular disturbance such as vertigo after watching revolving objects. The mean value of electronystagmographic abnormality in patients with hearing loss is greater than in patients with normal hearing. However, there is no statistical correlation between the level of hearing loss, electronystagmographic abnormality and severity of radiological deformity.

Unilateral sensorineural hearing loss and its aetiology in childhood: the contribution of computerised tomography in aetiological diagnosis and management

OBJECTIVES

The objective of this study was to identify factors correlated with the CT outcome and to examine the contribution of the CT scan in the aetiological diagnosis and management of unilateral sensorineural hearing loss in childhood.

METHODS

The records of 35 consecutively investigated patients by the Audiology Department of Great Ormond Street Hospital between January 1996 and June 1998 were reviewed. The CT results, population sample characteristics, initiation of further investigations after the CT results and management decisions based on the CT results were tabulated and analysed.

RESULTS

In a series of 35 consecutively investigated children with unilateral sensorineural hearing loss, 11 CT scans were identified as abnormal. The CT findings were: labyrinthitis ossificans (3), unilaterally dilated vestibular aqueduct (2), bilaterally dilated vestibular aqueduct (2), unilateral deformity of the cochlea ('Mondini') (1), unilateral severe labyrinthine dysplasia (1), unilateral markedly narrow internal acoustic meatus (1), bilaterally dilated lateral semicircular canals (1). The presence of progressive hearing loss was a significant predictor of abnormal CT outcome, while the severity of hearing loss was not. The CT scans offered valuable information regarding the aetiological diagnosis in all cases and, in addition, prompted the appropriate vestibular rehabilitation in three cases, further investigations in four (with dilated vestibular aqueduct) and hearing preservation counselling in two (bilateral DVA) (seven out of 35 = 20%).

CONCLUSION

All children with unilateral sensorineural hearing loss should have a CT scan of the petrous pyramids/IAMs performed at some stage, as not only aetiology but also prognosis and management of these cases may be significantly influenced by the CT outcome.

MR imaging of the cochlear modiolus: area measurement in healthy subjects and in patients with a large endolymphatic duct and sac

PURPOSE

To evaluate the cochlear modiolus with thin-section magnetic resonance (MR) imaging in healthy subjects and patients with a large endolymphatic duct and sac, and to assess whether the cochlea is normal or abnormal in patients with a large endolymphatic duct and sac.

MATERIALS AND METHODS

MR images were obtained in 10 ears in five volunteers (group 1), 40 ears in 20 patients with bilateral sensory hearing loss (group 2), three ears in two patients with Mondini malformation (group 3), and 12 ears in seven patients with a large endolymphatic duct and sac (group 4).

RESULTS

In groups 1 and 2, all modiolar areas were larger than 4.0 mm2. In group 3, each modiolus was smaller than 2.0 mm2. In group 4, modiolar areas were smaller than 2.0 mm2 in eight ears and were larger than 4.0 mm2 in four ears.

CONCLUSION

Findings in this study confirm that a large endolymphatic duct and sac is frequently associated with modiolar deficiency, but the modiolar area is normal in some cases. This result does not support the recently proposed hypothesis that hearing loss with a large endolymphatic duct and sac is caused by the transmission of subarachnoid pressure forces into the labyrinth through a deficient modiolus.

Diagnostic yield of high-resolution computed tomography for pediatric sensorineural hearing loss

OBJECTIVES/HYPOTHESIS

In recent years, relatively subtle inner ear anomalies have become apparent using high-resolution computed tomography (CT). The purpose of this study was to determine the diagnostic yield of high-resolution CT for pediatric sensorineural hearing loss (HL) (SNHL).

METHODS

A review was performed on the records of all children (<18 y of age) who had undergone CT of the temporal bones over a 5-year period, since the introduction of current CT techniques.

RESULTS

Three hundred eighty-three studies were performed in 351 subjects. The indication for the CT was SNHL or mixed HL in 157 children. Forty-nine (31%) of these studies revealed significant inner ear findings. Large vestibular aqueducts (LVAs) were reported in 15%, commonly in association with cochlear modiolar deficiencies. Modiolar deficiencies (11%) and other cochlear dysplasias (12%) followed LVA in frequency. The incidence of inner ear dysplasia in children with perinatal or postnatal risk factors was only slightly lower than those without (22% vs. 32%, P > .05). The rate of dysplasias did not correlate with SNHL severity, pattern of HL, or type of HL (mixed vs. sensorineural).

CONCLUSIONS

These findings suggest that radiographic imaging has a relatively high diagnostic yield in children with SNHL. These findings may be of value in counseling patients and guiding the management of their SNHL.

The large vestibular aqueduct syndrome: the role of cochlear implantation in its management

In recent years the large vestibular aqueduct syndrome has become an increasingly recognized cause of a progressive sensorineural hearing loss. Cochlear implantation, although not correcting the bony abnormality, does offer an avenue for rehabilitation for affected individuals and initial results are encouraging. Of 15 patients identified with the large vestibular aqueduct syndrome we have implanted seven (five adults and two children). All patients underwent an uneventful electrode insertion with uncomplicated postoperative periods. Three of our adult patients are showing very good initial results with BKB speech recognition scores of 100%, 74% and 66% with the implant alone. It is still early days with the children, but initial results are encouraging. A full review of the large vestibular aqueduct syndrome is given along with our results.

Cochlear implantation in children with enlarged vestibular aqueducts

OBJECTIVES

This report details our experience with cochlear implantation in children with both profound sensorineural HL (SNHL) and enlarged vestibular aqueducts (EVAs). It seeks to determine if the abnormal anatomy of EVA predisposes to any adverse events during or after cochlear implantation.

STUDY DESIGN

A retrospective review.

METHODS

Charts were reviewed for details of the procedure, complications, and audiologic outcome.

RESULTS

Between 8/25/93 and 9/16/98, 10 children with EVAs received cochlear implants, of whom 8 children (5 males, 3 females; mean age 7.8 y) had audiologic follow-up of at least 6 months. The implant was inserted without difficulty in all patients. Pulsatile clear fluid via the cochleostomy was observed in five patients, but was easily controlled in each instance. There have been no major complications, although two patient had short-lived postoperative vestibular symptoms and one child has experienced an intermittent pulsing sensation in her head. Speech perception measures were obtained using a battery of tests that assessed the children's ability to perceive speech in both open- and closed-set formats. Two patients were excluded because the implant was placed within the last 6 months. Of the remaining eight children identified with EVAs, seven (86%) demonstrated open-set word recognition.

CONCLUSIONS

These favorable results may be attributed in part to HL that occurs relatively late in childhood, allowing implantation in postlingual candidates. Cochlear implantation can be safely and effectively performed in children with SNHL associated with EVAs.

Multichannel cochlear implantation in children with large vestibular aqueduct syndrome

This study examined the postoperative performance of multichannel cochlear implantation in children with severe-to-profound sensorineural hearing loss secondary to large vestibular aqueduct syndrome. Five children between ages 4 and 13 years who had large vestibular aqueducts confirmed by computed tomography scans underwent implantation of a CLARION Multi-Strategy Cochlear Implant between January 1995 and June 1996 at Boys Town National Research Hospital. In addition to preoperative evaluations, they were examined postoperatively with their implants on a battery of open-set speech recognition tests at 3, 6, 12, and 18 months following initial stimulation. Results indicated a noticeable improvement in open-set speech recognition within the first 3 months of implant use compared to preimplant performance with hearing aids. All 5 patients demonstrated substantial benefit from their implants, but there was variation among the children in the rate and amount of improvement in speech recognition skills.

Management of the child with sensorineural hearing loss. Medical, surgical, hearing aids, cochlear implants

Optimal comprehensive management of a child with SNHL involves constructive dialogue and coordination with the child's family and teachers. Not all children with SNHL benefit from conventional amplification, even after parents have invested significant amounts of money in hearing aids. Parents may encounter frustration and disappointment if their children fail to achieve communicative and academic goals they have established in their own mind. If the child is a potential candidate for cochlear implantation, this decision not only involves the risks (albeit modest) of surgery but also often a substantial financial commitment to help defray the cost of this sophisticated electronic device. The parents may encounter conflicting advice from friends and members of the adult deaf community about the benefit of cochlear implantation. Throughout the course of all of these difficult considerations, the health professionals caring for a child with hearing loss should be a source for information, guidance, and support to the family.

Minimal, progressive, and fluctuating hearing losses in children. Characteristics, identification, and management

Referring to specific types of hearing loss as "minimal" or "mild" seems to imply that their effects are equally mild or negligible. A growing body of literature, however, supports the notion that such losses can have a significant impact on the communicative and educational development of young children. Although OME is considered a common childhood ailment, mounting evidence suggests that it is not always benign and may contribute to significant educational and communicative difficulties in some young children when accompanied by conductive hearing loss. Even very mild bilateral and unilateral SNHL seems to contribute to problems in the areas of social and emotional function, educational achievement, and communication in some children. Because these hearing losses are so mild, they may not be immediately recognized as the source of such difficulties. The purpose of this report is to heighten the general pediatrician's awareness of the significance of even very mild or minimal hearing losses in children. As the gatekeepers for children's health care, pediatricians are typically the primary recipients of parental expressions of concern and the initiators of evaluations or referrals to address such.

Three familial cases of hearing loss associated with enlargement of the vestibular aqueduct

The present report describes three familial cases of recessive hearing loss associated with enlargement of the vestibular aqueduct (EVA). Six siblings from three families showed EVA. The common characteristic of these patients was the presence of congenital, high-frequency, fluctuating sensorineural hearing loss. These cases suggest that EVA may be a useful discriminator between different types of recessive hearing loss.

Large endolymphatic sac. A congenital deformity of the inner ear shown by magnetic resonance imaging

Fluctuant and progressive hearing impairment in a patient with a wide vestibular aqueduct has been called the 'large vestibular aqueduct syndrome'. Recently reports of magnetic resonance imaging (MRI) studies describe enlargement of the endolymphatic sac and duct in patients shown to have large vestibular aqueducts by computed tomography (CT). A patient with progressive deafness was shown to have borderline or slightly enlarged vestibular aqueducts by re-formatted sagittal CT. However, MRI in axial and sagittal planes gave a more satisfactory demonstration of both aqueduct and endolymphatic sac enlargement.

Preoperative temporal bone computed tomography scan and its use in evaluating the pediatric cochlear implant candidate

Preoperative computed tomography (CT) scan evaluation of the temporal bones in cochlear implant candidates plays a crucial role in determining candidacy and the side of implantation. The CT scans allow the surgeon to carefully review the anatomy of the inner ear and mastoid cavity in order to predict any potential difficulties or complications that may be encountered during the implant insertion. We retrospectively reviewed 50 preoperative CT scans of the temporal bone in children who have been successfully implanted. In these scans, we assessed the degree of mastoid pneumatization, cochlear anatomy and patency, size of the vestibular aqueduct, cochlear aqueduct, and internal auditory canal. We analyzed our findings and measurements and compared our results with the degree of difficulty noted in the insertion of the implant, the number of electrodes inserted in each case, and the overall complication rate. From this radiographic review, we have created a checklist for cochlear implant surgeons in order to highlight key features that need to be recognized in the temporal bone scan in preoperative evaluation of cochlear implant candidates.

Magnetic resonance imaging of patients with large vestibular aqueducts

The vestibular aqueduct (VA) and endolymphatic sac (ES) were examined by magnetic resonance imaging in eight patients (14 ears) with large VAs, and the results were compared with those obtained in five normal volunteers (10 ears). It was not possible to identify either the VA or ES in any of the control ears. However, in all the 14 ears with a large VA, the VA was detected as a fluid-filled structure. In 12 ears the ES was seen to be markedly enlarged and also filled with fluid. In one ear, the volume of the fluid-filled space within the VA and ES was measured as 912 mm3 on serial images. Five patients (ten ears) were observed to have a fluid-filled VA and enlarged ES without cochlear anomalies and reported frequent episodes of sudden hearing loss and vertigo following exercise, long exposure to sunshine, minor trauma and the like. Two other patients (three ears) also had enlarged VA and ES as well as cochlear anomalies, but did not have episodes of sudden hearing loss and vertigo. These findings suggest that direct transmission of intracranial pressure changes to the inner ear or subsequent movement of endolymph in patients with a large VA may adversely influence a seemingly normal cochlea and vestibule.

Familial large vestibular aqueduct syndrome

The large vestibular aqueduct syndrome (LVAS) is a distinct clinical entity characterized by stepwise progressive sensorineural hearing loss associated with isolated enlargement of the vestibular aqueduct. A correlative clinical, audiologic, vestibular, cytogenetic, and radiographic analysis of a family with inherited LVAS was performed. The male proband and his affected brother are offspring of unaffected parents, and have no other abnormalities. Pedigree analysis suggests autosomal recessive or X-linked inheritance with variable expressivity of LVAS in this family. This study is the first description of familial inheritance of LVAS. LVAS may account for a significant number of patients with nonsyndromal, genetic sensorineural hearing loss. Future molecular analyses of this study family may identify the causative gene(s) in LVAS.

Inner ear malformations in patients with sensorineural hearing loss: detection with gradient-echo (3DFT-CISS) MRI

The sensitivity of different MRI sequences in the detection of inner ear malformations in patients presenting with sensorineural hearing loss (SNHL) and/or vertigo was evaluated. We studied 650 patients presenting with SNHL and/or vertigo, clinically not suspected of having inner ear malformations. The sensitivity of T1-weighted, Gd-enhanced T1-weighted and (when available) T2-weighted spin-echo images, and three-dimensional Fourier transformation-constructive interference in steady state (3DFT-CISS) gradient-echo images, to unexpected malformations was assessed. Inner ear malformations were found in 15 (2.3%) of these patients. Enlargement of the endolymphatic duct and sac was the most frequent malformation, found in 11 patients. The 3DFT-CISS images showed all lesions; the other sequences were less sensitive and the pathology was missed, partially or only retrospectively seen in 11 of the 15 patients. Therefore, in addition to the routine unenhanced and Gd-enhanced T1-weighted and T2-weighted images, thin gradient-echo (3DFT-CISS) images are necessary to detect all clinically unexpected inner ear malformations in patients presenting with vertigo and/or SNHL.

Advanced techniques in magnetic resonance imaging in the evaluation of the large endolymphatic duct and sac syndrome

The purpose of this report is to compare temporal bone computed tomography (CT) to high-resolution magnetic resonance (MR) imaging using a novel thin-section fast spin echo (FSE) pulse sequence in identifying and characterizing patients with large vestibular aqueduct syndrome. Sixteen patients with sensorineural hearing loss and a CT diagnosis of large vestibular aqueduct(s) underwent high-resolution fast spin echo magnetic resonance imaging with dual, 3-in phased array receiver coils centered over the external auditory canals. Magnetic resonance imaging parameters included axial and oblique sagittal fast spin echo with an effective slice thickness of 1 mm contiguous. Thirty-eight patients with 76 normal inner ears who underwent MR imaging using this technique had their endolymphatic duct measured. MR alone identified the enlarged endolymphatic sac seen along with the large endolymphatic duct in all cases. Three cases (five inner ears) with enlarged bony vestibular aqueducts on CT showed no evidence of endolymphatic duct or sac enlargement on MR. MR alone identified a single case of mild cochlear anomaly in conjunction with an enlarged endolymphatic duct and sac. In the normal population the size of the normal endolymphatic duct at its midpoint measured from 0.1 to 1.4 mm. Thin-section, high-resolution fast spin echo MR imaging of the inner ear may be superior to CT in the evaluation of patients with the large vestibular aqueduct syndrome.

Sensorineural hearing loss in patients with large vestibular aqueduct

In examining 181 patients (327 ears) with sensorineural hearing loss of unknown etiology and 25 people (50 ears) with normal hearing by high-resolution computed tomography (CT), the image of the large vestibular aqueduct (VA) was defined as being a visible large aperture (> or = 4 mm), and small distance between vestibule and traceable part of the VA nearest to the vestibule (> or = 1 mm). The large VA was found in 13 patients (23 ears, 7.0%); it was relatively frequent following hypoplastic cochlea (33 ears, 10.1%) in all the inner ear anomalies detected. In patients with large VA, high-frequency hearing was affected more than low frequency, and history of sudden hearing loss was observed frequently (61% of ears with large VA), which was found to be triggered by characteristic episodes such as minor head trauma, etc. Those clinical features were observed more in those without cochlear anomaly than in those accompanying cochlear anomaly. Pathogenesis of sensorineural hearing loss and characteristic fluctuation of hearing in those patients are discussed.

Vestibular function in patients with a large vestibular aqueduct

Four patients (7 ears) with a large vestibular aqueduct (VA) were examined for history of vertigo and vestibular function. Vertigo was observed in all the 4 patients. The caloric responses were significantly poorer in ears with a large VA than in the controls. On a patient with a large VA who had several attacks of sudden hearing loss and vertigo following minor head trauma, long-time exposure to sunshine, common cold, and exercise, vestibular function tests were performed several times; the caloric responses were found to fluctuate and direction changing apogeotropic positional nystagmus was observed. These findings suggest that in patients with a large VA, not only hearing but also the vestibular function are generally impaired. We believe than direct transmission of intracranial pressure changes to the inner ear or subsequent inner ear fluid movement through the large endolymphatic sac and duct have an influence on the cochlea and vestibule.

Value of Gd-DTPA-enhanced MR imaging of the labyrinth in patients with sudden hearing loss

Recent reports describe labyrinthine enhancement on MRI as a highly specific sign of labyrinthine disease. This paper reports 44 patients with unilateral sensorineural hearing loss (SNHL) and laboratory evidence of cochlear damage investigated with Gd-enhanced MR imaging. Enhancement of the cochlea was observed in only one patient with a lesion at the fundus of the internal auditory canal (IAC) that extended into the cochlea after Gd-DTPA administration. In one more patient, MR imaging demonstrated large vestibular aqueducts as underlying cause for his hearing loss, but no enhancement of the labyrinth was observed. No abnormal signal intensity on precontrast MR scans nor pathologic enhancement of the membranous labyrinth were identified in the other 42 patients. Gd-enhanced MR imaging appears to be insensitive in demonstrating labyrinthine disease and normal examination findings in a patient with sudden SNHL cannot exclude damage at the cochlear level.

Large vestibular aqueduct syndrome and stapes fixation

An abnormally large vestibular aqueduct has a well recognized association with inner ear anomalies and it has been assumed previously to be a variant of a Mondini type of deformity (Shuknecht, 1980; Emmett, 1985). The sole radiological finding in some patients with progressive sensorineural loss has been a large vestibular aqueduct (Valvassori and Clemis, 1978; Valvassori, 1983), which is now accepted as a separate clinical entity, i.e. the large vestibular aqueduct syndrome (LVAS). A case is presented which is believed to be the first reported with unilateral LVAS and stapes fixation and also the first stapes gusher described in association with LVAS.

The Enlarged Vestibular Aqueduct Syndrome (EVA Syndrome)

The presentation to the Department of Pediatric Otolaryngology at the Children's Hospital of Michigan of a series of patients with sensorineural hearing loss and enlargement of the vestibular aqueduct prompted exploratory tympanotomy in three patients (two unilateral and one bilateral), for a total of four ears. These explorations were prompted by progression and/or fluctuation of hearing levels. The discovery of abnormal round windows in all four ears with a post-traumatic fistula present in one ear suggested the presence of a new association. A previously undescribed association of an enlarged vestibular aqueduct, sensorineural hearing loss and round window abnormality with potential fistula formation was identified.

A review of the anatomy and physiology, literature review, and a prospective analysis with discussion of eight patients with enlarged vestibular aqueduct syndrome evaluated and treated at Children's Hospital of Michigan, is presented. We conclude that all children with sensorineural hearing loss should undergo extensive evaluation to determine etiology, including radiographic studies of the temporal bone. Further, the presence of an enlarged vestibular aqueduct should prompt the otolaryngologist to consider the presence of a round window abnormality and the potential for predisposition to perilymph fistula.

Enlargement of the cochlear aqueduct: fact or fiction?

Enlargement of the cochlear aqueduct (CA) is often mentioned in the otologic literature, usually in its purported association with sensory hearing loss, stapes gusher, and transotic cerebrospinal fluid leak. In CT scans of 100 ears, the diameter of the CA medial aperture was found to be highly variable, ranging from 0 to 11 mm, with a mean of 4.5 mm. In contrast, the otic capsule segment was very narrow in every case. It could be visualized in only 56% of cases, none of which exceeded 2 mm in diameter. Several published reports of supposed CA enlargement presented images of a dilated medial aperture that was well within the range of normal variability according to the present study. In a thorough review of the literature on radiology of the CA, we were unable to find a single published image that convincingly demonstrated enlargement of the otic capsule portion. As radiographic CA enlargement has not been convincingly reported to date, it appears to be an exceedingly rare or perhaps even nonexistent malformation. It is important to recognize than even a radiographically normal CA may be hyperpatent. It is theoretically possible for increased fluid flow to result from either deficiencies in intraluminal membrane baffles or subtle canal enlargement beneath the resolution limits of CT scanning. However, as fluid flow through a tube is regulated by its narrowest point, it is extremely improbable that stapes gusher, transotic CSF leak, and vigorous perilymphatic fistula are generated by the CA when CT scans show any portion of it to be very narrow. A substantial body of evidence points to a deficient partition between the internal auditory canal and inner ear as causative in such cases. We propose that the criteria for the diagnosis of CA enlargement on high-resolution CT scan be a diameter exceeding 2 mm throughout its course from the posterior fossa to the vestibule.

Sensorineural hearing loss

The authors emphasize the importance of early identification and early intervention concerning the management of children with Sensorineural Hearing Loss. The pediatrician plays a critical role in initiating the necessary clinical and audiological evaluations. Guidelines and treatment options are reviewed.