Enlarged Vestibular Aqueduct Syndrome (EVA syndrome)
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Enlarged Vestibular Aqueduct Syndrome (EVA syndrome) R3 陳泓里
1. Definition: early-onset, progressed or fluctuated sensorineural hearing loss detection of enlarged vestibular aqueduct by temporal bone image “Large endolymphatic duct and sac syndrome” 2. Anatomy and Physiology: Vestibular aqueduct(VA): a bony canal from medial wall of vestibule to the outer opening in the posterior aspect of petrous pyramid Endolymphatic duct(ED) : proximally from union of saccular and utricular ducts course parallels the common crus of SSC, PSC in VA Endolymphatic sac(ES): partially within the bony niche of posterior surface of petrous bone, partially within the posterior fossa dura layers tall epithelium with rugosity → regulating the volume, pressure and ionic composition of endolymph 3. Embryology: VA derives from a medial diverticulum of otocyst during 5th week of gestation. Inner ear structures attained its adult proportion in the midterm while VA has a straight course parallel the commom crus of PSC and SSC. VA became elongated while ED and ES are pulled downward as growth of posterior cranial vault in late prenatal and postnatal life VA acquires its normal adult shape as “ inverted J”. Short limb ( isthmus): 3~5 mm, parallels the commom crus Long limb: 3.5~11mm, normal 0.4~1.0 mm in width
4. Diagnostic criteria in image: Polytomography by lateral projection:Valvassori and Clemis(1968) Temporal bone high resolution CT (Swartz 1985) or MRI in axial view: A-P diameter >1.5 mm by midpoint of postisthmic segment Half way between common crus and external aperture
4. History review: 1791~ Carlo Mondini: autopsy of a boy born to be deaf Enlarged VA is frequent in “Mondini Dysplasia”
1960~ Study of VA by polytomography in Meniere’s disease. 1978
Valvassori and Clemis(1968), Schuknecht(1972) Valvassori and Clemis ( laryngoscope) Large vestibular aqueduct associated with SNHL 50/3700 patients (1.5%) by polytomography Female, bilateral predominance, most with other inner anomaly: enlarged vestibule or SCCs, hypoplastic cochlea….. → Arrest of inner development in embryo, Emmett 47/ 5368 ears, audiometric and vestibular function evaluation → a distinct clinical entity, possibly a variant of Mondini deformity HRCT consistent with tomography
5. Epidemiology Most common inner ear anomaly demonstrated in modern image Incidence: Valvassori and Clemis(1978) :1.5% , Emmett(1985) :1 % Levenson(1989): 0.64% Would be rarer in general population Female predominance (56%), Bilateral predominance(72~81%) 60%~88% associated with other inner anomaly: enlarged vestibule or SCC(50~63%), hypoplastic cochlea(16~28%). 6. Pathophysiology of SNHL in EVA syndrome: Valvassori and Clemis (1978): arrest of inner development in embryo? Gussen(1985): pressure with the dilated ED & ES and erosion of VA Levenson(1989): hyperosmotic and hyperproteineous sac contents refluxed into cochlea Okamoto(1998):higher intensity of ES and ED by CT and spin-echo MRI than CSF → protein rich, hyperosmolar endolymph in sac Belenky(1993): round window anomaly in EVA → perilymphatic fistula 7. Clinical presentation: Progressive and early-onset SNHL, Fluctuated SNHL Preceding insult (minor head trauma, airplane flight) Delayed speech Nonspecific and mild aural and vestibular symptoms 7.Genetics, inheritance and association with Pendred syndrome Pedigree analysis: Tong(1997) 39% family occurrence (13/33) Heterogeneity in inheritance: AR, incomplete AD, multifactorial ?
Molecular genetics of hereditary hearing loss EVA in syndromic hearing loss ( Pendred , Branchiootorenal syndrome) Pendred syndrome: most common syndromic hereditary hearing loss 10% of hereditary hearing loss PDS gene (7q31) with AR inheritance goiter, iodine organization defect, hypothyroidism,SNHL EVA, cochlear or vestibular dysplasia Cremers(1998) Phelps(1998): 100% PDS with EVA by imaging Abe(1999):localize gene responsible for EVA to 7q31( PDS) different mutations with different phenotype → syndromic Pendred syndrome and nonsyndromic EVA Everett(1997),Coyle(1998),Van Hauwe(1998),Usami(1999): Identification of >30 mutation points: missence, frameshift Reardon(2000): 41/57(72%) of EVA diagnosed as Pendred syndrome EVA is the most likely presentation of Pendred’s syndrome Pendrin: 5kb sulfate transporters, expressed in thyroid tissue ↓Sulphation of thyroglobulin, ↓ iodine organization The role of Pendrin in cochlear development ? Hypothyroidism impair inner ear development in embryo? Direct effect of Pendrin in cochlear development 8. Evaluation and diagnosis: History taking: FH, preceding insult, prenatal insult Physical examination Audiometry: Pure tone: moderate to profound, downward sloping SNHL Speech audiometry: SRT, Discrimination score Vestibular function evaluation: peripheral vestibulopathy Image study: Polytomography: poor resolution and high radiation exposure Temporal bone HRCT: VA and other inner ear bony structures High-resolution MR: membranous labyrinth, including ED and ES * For Pendred syndrome: Perchlorate dischage test: 10~80% discharge Thyroid function test: subclinical hypothyroidism Mutation analysis of PDS gene
Management recommendation: Early detection: congenital or early-onset sensorineural deafness imaging study No medical or surgical therapy recommended in progressive SNHL Family and patient’s education and warning to prevent head trauma Auditory rehabilitation with hearing aid fitting: as early as possible Experience in surgical intervention: Endolymphatic sac occlusion: block the reflux and pressure gradients detrimental to the inner ear Intraluminal: Wilson(1997) hearing stablization in 6/7 ears Intraluminal & extraluminal: Welling(1999): significant postoperative loss of hearing and not recommended Endolymphatic subarachnoid shunt Emmett(1985): no improvement in 4 patients Jacker and De la Cruz(1989): 4/7 with postoperative hearing drop Cochlear implant : Bent (1999): 10 patients of EVA undergo CI, 7/8 gained good speech recognization. Postlingual hearing loss is good candidates for CI. Cochleotomy gusher does not prevent successful implantation. Reference 1.
Valvassori G, Clemis J: The large vestibular aqueduct syndrome. Laryngoscope 1978, 88:723-748.
Cremers W, Bolder C, Admiraal R, et al.: Progressive sensorineural hearing loss and a widened vestibular aqueduct in pendred syndrome. Arch Otolaryngol Head Neck Surg 1998, 124:501-505
Emmett J: The large vestibular aqueduct syndrome. Am J Otol 1985, 6:387-403.
Arcand P, Desrosiers M, Dube J, et al.: The large vestibular aqueduct syndrome and sensorineural hearing loss in the pediatric population. J Otolaryngol 1991, 20:247-250.
Belenky W, Madgy D, Leider J, et al.: The enlarged vestibular aqueduct syndrome. Ear Nose Throat J 1993, 72:746-751.
Jackler R, De La Cruz A: The large vestibular aqueduct syndrome. Laryngoscope 1989, 99:1238-1243.
Levenson M, Prasier S, Jacobs M, et al.: The large vestibular aqueduct syndrome in children. Arch Otolaryngol Head Neck Surg 1989, 115:54-58.
Zalzal G, Tomaski S, Vezina L, et al.: Enlarged vestibular aqueduct and sensorineural hearing loss in childhood. Arch Otolaryngol Head Neck Surg 1995, 121:23-28.
Okamoto K, Ito J, Furusawa T, et al.: MRI of enlarged endolymphatic sacs in the large vestibular aqueduct syndrome. Neuroradiology 1998, 40:167-172.
10. Gussen R: The endolymphatic sac in Mondini disorder. Arch Otorhinolaryngol 1985, 242:71-76. 11. Tong K, Harnsberger H, Dahlen R, et al.: Large vestibular aqueduct syndrome: a genetic disease? AJR Am J Roentgenol 1997, 168:1097-1101. 12. Everett L, Glaser B, Beck J, et al.: Pendred syndrome is caused by mutations in a putative sulphate transporter gene (PDS). Nat Genet 1997, 17:411-422. 13. Cremers C, Admiraal R, Huygen P, et al.: Progressive hearing loss, hypoplasia of the cochlea and widened vestibular aqueducts are very common features in pendred's syndrome. Int J Pediatr Otorhinolaryngol 1998, 45:113-123. 14. Phelps P, Coffey R, Trembath R, et al.: Radiological malformations of the ear in pendred syndrome. Clin Radiol 1998, 53:268-273. 15. Abe S, Usami S, Hoover D, et al.: Fluctuating sensorineural hearing loss associated with enlarged vestibular aqueduct maps to 7q31, the region containing the pendred gene. Am J Med Genet 1999, 82:322-328. 16. Usami S, Abe S, Weston M, et al.: Non-syndromic hearing loss associated with enlarged vestibular aqueduct is caused by PDS mutations. Hum Genet 1999, 104:188-192. This paper discusses the specific mutations found within the PDS gene responsible for EVA. 17. Reardon W, O'Mahoney C, Trembath R, et al.: Enlarged vestibular aqueduct: a radiologic marker of pendred syndrome, and mutation of the PDS gene. Q J Med 2000, 93:99-104. This paper discusses the critical role of PDS mutation in the generation of EVA and suggests a new definition for Pendred syndrome. 18. Hirsch B, Weissman J, Curtin H, et al.: Magnetic resonace imaging of the large vestibular aqueduct. Arch Otolaryngol Head Neck Surg 1992, 118:1124-1127. 19. Wilson D, Hodgson R, Talbot J: Endolymphatic sac obliteration for the large vestibular aqueduct syndrome. Am J Otol 1997, 87:101-106. 20. Welling D, Martyn M, Miles B, et al.: Endolymphatic sac occlusion for the enlarged vestibular aqueduct syndrome. Am J Otol 1998, 19:145-151. 21. Welling D, Slater P, Martyn M, et al.: Sensorineural hearing loss after occlusion of the enlarged vestibular aqueduct. Am J Otol 1999, 20:338-343. 22. Bent J, Chute P, Parisier S: Cochlear implantation in children with the enlarged vestibular aqueduct syndrome. Laryngoscope 1999, 109:1019-1022. 23. Lasak J, Welling D: The enlarged vestibular aqueduct syndrome. Current Opinion in Otolaryngol Head Neck Surg 2000,8:380-383