Large Vestibular Aqueduct Syndrome

Large vestibular aqueduct syndrome (also known as enlarged endolymphatic duct and sac syndrome), is the most frequent cause of bilateral progressive sensorineural hearing loss in children. While the deformity of the endolymphatic duct and sac is congenital, the hearing loss is acquired and thought to be related to minor head trauma (the exact mechanism is unknown).

The vestibular aqueduct is considered enlarged on CT when it measures ≥ 1 mm at its midpoint and ≥ 2 mm at the operculum. T2-weighted images show a high signal intensity enlarged endolymphatic sac.

10%-15% of patients have Pendred syndrome, which is the most common syndromic cause of hearing loss. It is an inherited disorder consisting of a dyshormonogenic goiter (cannot organify iodide efficiently) and sensorineural hearing loss and may be accompanied by vestibular symptoms. Imaging shows a large vestibular aqueduct and inner ear malformations. The perchlorate discharge test is used for diagnosis.

References

• Goldfeld M, Glaser B, Nassir E, Gomori JM, Hazani E, Bishara N. CT of the ear in Pendred syndrome. Radiology. 2005 May;235(2):537-40.
• Naganawa S, Koshikawa T, Fukatsu H, Ishigaki T, Nakashima T. Serial MR imaging studies in enlarged endolymphatic duct and sac syndrome. Eur Radiol. 2002 Dec;12 Suppl 3:S114-7.
• Vijayasekaran S, Halsted MJ, Boston M, Meinzen-Derr J, Bardo DM, Greinwald J, Benton C. When is the vestibular aqueduct enlarged? A statistical analysis of the normative distribution of vestibular aqueduct size. AJNR Am J Neuroradiol. 2007 Jun-Jul;28(6):1133-8.