Abstract
Introduction
An enlarged vestibular aqueduct (EVA) results in hearing loss which is often progressive and heterogenous, the long-term natural history of which is not well understood. Patients born before the era of newborn hearing screening can present as adults with previously undiagnosed EVA.
Methods
A retrospective chart review of patients seen at a tertiary adult academic otologic clinic from 2004 to 2012 were reviewed and cases of EVA were identified.
Results
Adult EVA was found to present with a mixed progressive hearing loss with absent stapedial reflexes.
Conclusion
Enlarged vestibular aqueduct abnormality can present in adulthood and mimic other more common pathology such as otosclerosis.
1
Introduction
The enlarged vestibular aqueduct (EVA) is an abnormality of labyrinthine anatomy that can lead to hearing loss, often in a progressive fashion. The hearing loss can be sensorineural or mixed in nature, with a conductive component in the low frequencies. The pathophysiology of this cochlear conductive hearing loss is not completely understood, but appears to involve leakage of sound energy out of a third mobile window, the endolymphatic duct . With the advent of newborn hearing screening along with routine hearing screening upon school entry in most advanced countries, EVA is most often diagnosed in childhood. High-resolution computed tomography (CT) scans can visualize the lesion well. There is no universally agreed-upon size criteria for when a vestibular aqueduct is considered enlarged , but a rough rule of thumb is if the vestibular aqueduct is wider than the width of the posterior semicircular canal . The clinical presentation of EVA is highly variable with sensorineural hearing loss and mixed hearing losses reported .
Most reports on EVA involve children, but here we present three cases of newly diagnosed EVA causing mixed hearing loss in adults with clinical presentation closely mimicking otosclerosis. One of these patients had extensive audiograms available dating to the 1960s and these are presented in detail as little is known of the natural history of EVA in adults. To our knowledge, this represents the longest reported audiometric follow up of an individual with EVA.
2
Methods
Institutional review board (IRB) approval for this study was obtained. The computerized medical records of adult patients seen as part of a tertiary adult otology practice were reviewed and cases that had definitive evidence of EVA on CT scan were selected. Audiograms were selected for analysis and presentation. Audiograms predating 1969 were converted to 1969 ANSI standards. Ipsilateral stapedial reflexes, also called acoustic reflexes, were measured for each patient using an immittance bridge. The probe was placed in the test ear and a pure tone stimulus was presented at each frequency with increasing intensity until either a monophasic or biphasic response from the stapedius muscle was obtained or the limits of the equipment were reached .
2
Methods
Institutional review board (IRB) approval for this study was obtained. The computerized medical records of adult patients seen as part of a tertiary adult otology practice were reviewed and cases that had definitive evidence of EVA on CT scan were selected. Audiograms were selected for analysis and presentation. Audiograms predating 1969 were converted to 1969 ANSI standards. Ipsilateral stapedial reflexes, also called acoustic reflexes, were measured for each patient using an immittance bridge. The probe was placed in the test ear and a pure tone stimulus was presented at each frequency with increasing intensity until either a monophasic or biphasic response from the stapedius muscle was obtained or the limits of the equipment were reached .
3
Results
3.1
Patient 1
Patient 1 is a 61-year-old male who presented for evaluation of progressive bilateral sensorineural hearing loss since childhood and believed that his hearing loss developed following the measles and the mumps at approximately age 3. He perceived hearing as worse in the left ear and began using a hearing aid in the left ear in the early 1970s and on presentation to our clinic was wearing hearing aids in both ears. In the 1990s he experienced a sudden hearing loss in his right ear and subsequently underwent a right middle exploration, the records of which were unavailable for review.
Physical exam revealed a normal binocular microscopic exam bilaterally. Audiograms revealed a left sloping mild to profound and right sloping mild to severe sensorineural hearing loss in 1963, progressing to a bilateral severe to profound sloping sensorineural hearing loss in 2012. The audiometric results of Patient 1 are presented in detail, shown in Fig. 1 A–E , as they present a rare window on the natural history of hearing loss in EVA. Speech discrimination in 2012 was 32% in the left ear and 48% in the right ear. Stapedial reflexes were not performed until after the patient had undergone left cochlear implantation. Stapedial reflexes were tested at 100 dB at 500 Hz and 4000 Hz and 105 dB at 1000 Hz and 2000 Hz, but were absent bilaterally. CT scan demonstrated enlarged vestibular aqueducts bilaterally, with the left vestibular aqueduct enlarged to a greater degree than the right ( Fig. 2 ) EKG revealed a normal rate and rhythm with a QT interval that was at the high end of normal ( Fig. 3 ). At the age of 62, the patient underwent cochlear implantation of the Nucleus 24RE with the Freedom processor in his left ear. He had no residual hearing in that ear post-surgery ( Fig. 1 F). His performance with the cochlear implant 3.5 months after implant activation is shown in Fig. 1 H.
3.2
Patient 2
Patient 2 is a 43-year-old male who presented for evaluation of lifelong bilateral mixed hearing loss. He demonstrated a large conductive component and used a hearing aid only in is left ear. The patient reported an otologic surgery on his ear around 1985 and could not recall the specifics of this procedure, but reported that his hearing was no different following the procedure. A CT of the temporal bones demonstrated bilateral enlargement of the vestibular aqueducts ( Fig. 4 ). Additionally, a stapes prosthesis was evident on the left extending to the oval window ( Fig. 5 ). The CT of the temporal bones was otherwise normal. An EKG was strongly recommended to the patient, but he refused.
