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EVA and did not investigate other less common temporal bone anomalies. Further study may thus be warranted to determine the possible role of such anomalies in the hear- ing loss phenotype of patients with EVA.

at 250 Hz is related to larger temporal bone measure- ments. When controlling for PTA and midpoint temporal bone measurements, the correlation between hearing loss at 250 Hz and the likelihood of progression is weak- ened, thus showing that the strength of temporal bone measurements is an indicator of progression. Overall, our data indicate that hearing levels at 250 Hz alone may be a sensitive clinical indicator in patients with EVA. Our data support the findings of Boston et al., 9 which showed a similar correlation in ears with a mixed hearing loss between 250 and 1,000 Hz. As discussed by Zhou et al., 20 the etiology of low- frequency, predominantly mixed hearing loss is uncer- tain. Increased intralabyrinthine fluid pressure or a possible third inner ear window phenomenon has been proposed as an etiology for this hearing loss. The rela- tionships shown in the current study between temporal bone measurements, hearing loss progression, and hear- ing loss at 250 Hz may support the abovementioned etiologic theory that larger vestibular aqueducts cause increased inner ear fluid pressure; in turn, fluid pres- sure may lead to a high rate of progression and the presence of hearing loss at 250 Hz. Patients with bilateral EVA had a significantly higher likelihood of having SLC26A4 mutations and of having Pendred syndrome than did patients with unilat- eral EVA. Our analysis of the ears of patients with hearing loss revealed that mutations were present at a higher rate in patients with bilateral EVA than in those with unilateral EVA. The presence of mutations overall did not increase the likelihood of progressive hearing loss or the severity of hearing loss in either EVA group. Specifically, in the ears of patients with bilateral EVA and hearing loss, the presence of mutations increased the likelihood of hearing loss progression. These findings support previously published data 25 indicating that sin- gle mutations contribute to the EVA phenotype. These single mutations, together with other as yet undeter- mined mutations, are thought to be responsible for the hearing loss phenotype. 23,25 The audiometric phenotype was similar in patients with unilateral and bilateral EVA. Because of the rela- tively high rate of hearing loss progression in patients with unilateral EVA, we feel that it is prudent to recom- mend close audiometric monitoring. Families and patients should be made aware of the possibility that a unilateral imaging finding does not necessarily signify that the pro- cess occurring within the membranous labyrinth is a unilateral process and that the development of bilateral hearing loss is quite common. Additionally, they should be advised that SLC26A4 testing is a valuable diagnostic adjunct in the evaluation of all patients with EVA. Our study has several limitations. Given that all of our data were based on previously collected imaging and audiometric results, biases may have been introduced regarding how data were entered into the database and which patients were included in the database. Children who did not receive an imaging study of the inner ear did not meet our inclusion criteria, thus making the true prev- alence of unilateral EVA in the total population of children with SNHL difficult to assess. Also, we examined only

CONCLUSION Children with unilateral EVA have a significant risk of hearing loss progression. Hearing loss in the ear contra- lateral to the EVA is common, suggesting that unilateral EVA is a bilateral process despite an initial unilateral imaging finding. In contrast to bilateral EVA, unilateral EVA is not associated with Pendred syndrome, but may have a different etiology. Clinicians should become knowledgeable regarding the implications of this disease process so that families can be counseled appropriately. BIBLIOGRAPHY 1. Jackler RK, Luxford WM, House WF. Congenital malformations of the inner ear: a classification based on embryogenesis. Laryngoscope 1987; 97:2–14. 2. Mafong DD, Shin EJ, Lalwani AK. Use of laboratory evaluation and radiologic imaging in the diagnostic evaluation of children with sensori- neural hearing loss. Laryngoscope 2002;112:1–7. 3. Antonelli PJ, Varela AE, Mancuso AA. Diagnostic yield of high-resolution computed tomography for pediatric sensorineural hearing loss. Laryngo- scope 1999;109:1642–1647. 4. Preciado DA, Lim LHY, Cohen AP, et al. A diagnostic paradigm for childhood idiopathic sensorineural hearing loss. Otolaryngol Head Neck Surg 2004;131:804–809. 5. Madden C, Halsted M, Benton C, Greinwald JH, Choo DI. Enlarged vestibular aqueduct syndrome in the pediatric population. Otol Neurotol 2003;24:625–632. 6. Valvassori GE, Clemis JD. The large vestibular aqueduct syndrome. Laryngoscope 1978;88:723–728. 7. Jackler RJ, De La Cruz A. The large vestibular aqueduct syndrome. Laryngoscope 1989;99:1238–1243. 8. Antonelli PJ, Nall AV, Lemmerling MM, Mancuso AA, Kubilis PS. Hearing loss in children with cochlear modiolar defects and large vestibular aqueducts. Am J Otol 1998;19:306–312. 9. Boston M, Halsted M, Meinzen-Derr J, et al. The large vestibular aqueduct: a new definition based on audiologic and computed tomogra- phy correlation. Otolaryngol Head Neck Surg 2007:136:972–977. 10. Spiegel JH, Lalwani AK. Large vestibular aqueduct syndrome and endo- lymphatic hydrops: two presentations of a common primary inner-ear dysfunction? J Laryngol Otol 2009;123:919–922. 11. Vijayasekaran S, Halsted MJ, Boston M, et al. When is the vestibular aqueduct enlarged? A statistical analysis of the normative distribution of vestibular aqueduct size. Am J Neuroradiol 2007;28:1133–1138. 12. Zalzal GH, Tomaski SM, Gilbert Vezina L, Bjornsti P, Grundfast KM. Enlarged vestibular aqueduct and sensorineural hearing loss in child- hood. Arch Otolaryngol Head Neck Surg 1995;121:23–28. 13. Mori T, Westerberg BD, Atashband S, Kozak FK. Natural history of hearing loss in children with enlarged vestibular aqueduct syndrome. J Otolaryngol Head Neck Surg 2008;37:112–118. 14. Grimmer JF, Hedlund G. Vestibular symptoms in children with enlarged vestibular aqueduct anomaly. Int J Pediatr Otorhinolaryngol 2007;1: 275–282. 15. Levenson MJ, Parisier SC, Jacobs M, Edelstein DR. The large vestibular aqueduct syndrome in children. Arch Otolaryngol Head Neck Surg 1989;115:54–58. 16. Lai CC, Shiao AS. Chronological changes of hearing in pediatric patients with large vestibular aqueduct syndrome. Laryngoscope 2004;114: 832–838. 17. Dewan K, Wippold J II, Lieu JE. Enlarged vestibular aqueduct in pediat- ric sensorineural hearing loss. Otolaryngol Head Neck Surg 2009;140: 552–558. 18. Berrettini S, Forli F, Neri E, Salvatori L, Casani AP, Franceschini SS. Large vestibular aqueduct syndrome: audiological, radiological, clinical, and genetic features. Am J Otolaryngol 2005;26:363–371. 19. Preciado DA, Lawson L, Madden C, et al. Improved diagnostic effective- ness with a sequential diagnostic paradigm in idiopathic pediatric sensorineural hearing loss. Otol Neurotol 2005;26:610–615. 20. Zhou G, Gopen Q, Kenna MA. Delineating the hearing loss in children with enlarged vestibular aqueduct. Laryngoscope 2008;118:2062–2066. 21. Colvin IB, Beale T, Harrop-Griffiths K. Long-term follow-up of hearing loss in children and young adults with enlarged vestibular aqueducts: relationship to radiologic findings and Pendred syndrome diagnosis. Laryngoscope 2006;116:2027–2036.

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