Volume 6, Issue 3 , Pages 125-127, September 2011
Non-syndromic bilateral enlarged vestibular aqueducts in two siblings
Article Outline
Abstract
Enlarged vestibular aqueduct is one of the most frequent inner ear malformations with early manifested sensorineural hearing loss. It is often associated with Pendred syndrome. The non-syndromic familial enlarged vestibular aqueduct entity is less described with only a few cases reported in the literature. It is thought to be a varying presentation on the phenotypic spectrum of genetic mutation in the same locus of chromosome 7q31. The familial inheritance has been suspected to be autosomal recessive. In this case report, we present a patient who presented to the clinic with hearing loss after blunt head trauma with a soccer ball. Suspected enlarged vestibular aqueduct was confirmed to be bilateral on CT scan of the temporal bones. Additional inquiry into the family history revealed that her sister also had bilateral sensorineural hearing loss at an early age. Unpredictably, bilateral enlarged vestibular aqueducts were confirmed in the sister with similar imaging modality. The clinical presentation, diagnosis, and treatment strategies are reviewed along with the current literature.
Keywords: Enlarged vestibular aqueduct, Familial, Hearing loss, Non-syndromic
1. Introduction
Enlarged vestibular aqueduct (EVA), an entity first described by Valvassori and Clemis in 1978 [16], is the most common CT scan abnormality of the inner ear in children with sensorineural hearing loss (SNHL). Anatomically, the vestibular aqueduct is the bony canal in the temporal bone transmitting the endolymphatic duct and its associated veins. The normal diameter of the vestibular aqueduct measured from external aperture to the common crus of utricle and saccule is 0.62
mm. When the bony canal is radiographically enlarged to more than 1.5mm, the endolymphatic duct is also found to be dilated. Thought to result from a congenital malformation of the temporal bone, EVAs predispose the patient to early onset of sensorineural hearing loss, vestibular disturbance, and ataxia. Seemingly minor head trauma may precipitate such symptoms. Description of EVAs associated with congenital syndromes such as Pendred has been well documented in literature. The non-syndromic or familial presentation has been recently recognized and, up to date, only five reports of familial non-syndromic EVAs were observed in siblings. We present our case of non-syndromic familial EVA with the literature review.
2. Clinical presentation
A 12-year-old female was referred to pediatric otolaryngology clinic for persistent and worsening hearing loss and resolved vertigo after blunt head trauma by a soccer ball. She was a previously healthy female born to normal hearing parents. Her birth history revealed that the pregnancy was full-term with normal spontaneous vaginal delivery and absence of postnatal complications. She passed her newborn hearing screening exam but was noted to have right sensorineural hearing loss at age 3 requiring hearing aids. She had no speech or motor delays. Her physical exam was significant for normal auricles, patent external ear canal, normal mobile tympanic membranes, and absence of syndromic facial features. Her neck exam revealed the absence of neck mass or goitre. Her audiogram showed bilateral severe to profound sensorineural hearing loss. Compared to her pre-trauma audiogram, she had 5–10dB further sensorineural hearing loss on the right ear and 60–100dB new SNHL on the left ear (Fig. 1). A CT scan of the temporal bones was ordered which revealed bilateral enlarged vestibular aqueducts measuring 2.2mm on the right and 2.6mm on the left (Fig. 2). Her family history was significant for her older sister who also had bilateral severe to profound sensorineural hearing loss at age 6 and had been fitted with hearing aids since then. The sibling did not have identifiable syndromic characteristics, neck mass, or delays. With this clinical picture, it was suggested that her sibling undergo evaluation for enlarged vestibular aqueduct at the time. The suspected enlarged vestibular aqueduct was confirmed in the older sibling with the right and left vestibular aqueducts measuring 2.3mm and 2.2mm, respectively. The patients and her family were appropriately counselled and hearing aids were fitted for the patient. Additionally, they were sent for genetic mutation testing including pendrin, and connexin 26. However, their insurance carriers did not approve of such expensive tests.
Fig. 1.
Patient's pre-trauma and post-trauma audiograms (Left-X, Right-0).
Fig. 2.
Axial CT scan of patient's temporal bones with enlarged vestibular aqueducts marked by white arrows.
3. Discussion
Enlarged vestibular aqueduct is suspected in children with new-onset early childhood hearing loss, hearing loss in children with blunt head trauma, episodic ataxia or disequilibrium with hearing deterioration, or progressive or fluctuating hearing loss with normal middle ear function [17]. Enlarged vestibular aqueducts present with varying degree of sensorineural hearing impairment as well as conductive hearing loss [1]. Zhou et al. had analyzed 82 ears and found that mixed hearing loss was the predominant feature found in about 74% of this group, and SNHL and conductive hearing loss (CHL), 20% and 6%, respectively [19]. The conductive component seems to be explained by the stiffening of the stapes due to high hydrostatic pressure or the phenomenon of the large vestibular aqueduct acting as the “third window”.
The pathologic mechanisms for the sensorineural hearing loss have been proposed and they range from damage to neuroepithelium from reflux of hypersomolar protein content of endolymphatic sac to cochlear duct [10], to electrolyte imbalance from accumulation of large volumes of endolymph, to mixing of endolymph and perilymph from congenital weak inner ear membranes [10], [14], and to transmission of pressure fluctuations of cerebral spinal fluid (CSF) to inner ear through the abnormally larger endolymphatic duct [2].
The hearing loss can be progressive with loss of about an average of 4dB per year [5], [9]. Minor head trauma has been implicated in precipitating acute hearing loss. Other precipitating etiologies include acoustic trauma, Valsalva maneuver, scuba diving, lifting, playing wind instruments, or airplane flights. Bilateral EVAs are more common than unilateral, and occur more commonly in females than males.
Large vestibular aqueduct has been described being linked to genetic syndromes such as branchio-oto-renal syndrome, Noonan syndrome, Waardenburg syndrome, and most commonly Pendred syndrome. The familial or non-syndromic form has been documented as well in five other case reports [7], [11], [12], [13]. It appears that the familial form has been mapped to 7q31, which is the same locus as the Pendred syndrome gene SLC26A4 (PDS) gene, but patients are negative for the perchlorate discharge test. Kim et al. has perform genetics studies on a patient with enlarge vestibular aqueduct homozygous for the H723R gene and family members with H723R heterozygous mutation.
Imaging is usually a computed tomography of the temporal bones which will confirm the presence of enlarged vestibular aqueduct larger than 1.5mm. MRI can also give additional information regarding cochlear or vestibular anomalies [4]. However, MRI has not been established as the standard of care to evaluate for EVA, therefore it was not used to evaluate the patients in this clinical setting.
Medical therapies which have been suggested include hyperbaric oxygen, and corticosteroids with anecdotal results. Surgical options have not been established as results have not been standardized. Endolymphatic decompression or endolymphatic obliteration have resulted in no changes in hearing and in some cases produced worse hearing loss [8], [18]. When hearing loss and speech discrimination severely deteriorate, the patient can be evaluated for cochlear implant with reported good successful outcomes. Intraoperative finding of perilymph gusher has been commonly associated with the cochleostomy. However, intraoperative sealing of the gusher can be achieved with connective tissue, fibrin, bone pate, and/or connective tissue such as fascia or muscle. Patients who develop intraoperative gushers may not experience any postoperative effects. However, more commonly the patients experience nausea or vomiting that can last between 1 and 10 days [15].
4. Conclusion
Enlarged vestibular aqueduct can be associated with syndromic or non-syndromic etiologies. Familial EVA causes progressive hearing loss with a genetic mutation within the same locus as the syndromic entity. It may be underdiagnosed in the family of patients presenting with the above complaints. We recommend that a complete family history should be obtained and suspected siblings undergo evaluation for EVA when there is a diagnosis within the family. Early detection and diagnosis can prevent deterioration of hearing and prompt early consultation with a geneticist.
References
- . Three familial cases of hearing loss associated with enlargement of the vestibular aqueduct. Ann. Otol. Rhinol. Laryngol. 1997;106:1063–1069
- . Hearing loss with cochlear modiolar defects and large vestibular aqueducts. Am. J. Otolaryngol. 1998;19(3 (May)):306–312
- . MR evaluation of vestibulocochlear anomalies associated with large endolymphatic duct and sac. AJNR Am. J. Neuroradiol. 1999;20(8 (September)):1435–1441
- . Familial enlarged vestibular aqueduct syndrome. Am. J. Otolaryngol. 2001;22:286–290
- Familial large vestibular aqueduct syndrome. Laryngoscope. 1992;106:960–965
- . The large vestibular aqueduct syndrome. Laryngoscope. 1989;99(12 (December)):1238–1242
- . Two siblings with isolated large vestibular aqueduct syndrome. J. Otolaryngol. Head Neck Surg. 2008;37(2 (April)):E55–E58
- . A Family of H723R mutation for SLC26A4 associated with enlarged vestibular aqueduct syndrome. Clin. Exp. Otorhinolaryngol. 2009 June;2(2):100–102
- . The large vestibular aqueduct syndrome in children. A review of 12 cases and the description of a new clinical entity. Arch. Otolaryngol. Head Neck Surg. 1989;115(1 (January)):54–58
- . Isolated large vestibular aqueduct syndrome in a family. Ann. Otol. Rhinol. Laryngol. 2000;109(1 (January)):40–44
- . Familial isolated unilateral large vestibular aqueduct syndrome. ORL J. Otorhinolaryngol. Relat. Spec. 2003;65(1 (January–February)):45–48
- . Large vestibular aqueduct syndrome and endolymphatic hydrops: two presentations of a common primary inner-ear dysfunction?. J. Laryngol. Otol. 2009;123:919–921
- . The large vestibular aqueduct-case report and review of literature. Acta Otolaryngol. 2006;126:788–795
- . The large vestibular aqueduct syndrome. Laryngoscope. 1978;88:723–728
- . Enlarged vestibular aqueduct in two male siblings. Dev. Med. Child Neurol. 2002;44:706–711
- . Endolymphatic sac obliteration for large vestibular aqueduct syndrome. Am. J. Otolaryngol. 1997;18(1 (January)):101–106discussion 106–7
- . Delineating the hearing loss in children with enlarged vestibular aqueduct. Laryngoscope. 2008;118:2062–2066
PII: S1871-4048(10)00038-9
doi:10.1016/j.pedex.2010.05.004
© 2010 Elsevier Ireland Ltd. All rights reserved.
Volume 6, Issue 3 , Pages 125-127, September 2011
