Vestibular aqueduct syndrome.

The vestibular aqueduct is a small, bony canal that extends from the vestibule to the posterior surface of the petrous bone. The aqueduct contains the endolymphatic duct, which enlarges and ends blindly in the endolymphatic sac on the posterior surface of the petrous bone. Vestibular aqueduct syndrome is one of the various causes of sensorineural hearing loss. The syndrome can be unilateral or bilateral. Hearing loss is often of the high-frequency variety and often progressive.

Recent reports indicate that patients who have a large vestibular aqueduct are merely predisposed to the development of hearing loss, and that this loss might not be truly congenital. [1] This syndrome is perhaps four times as common as other bony inner ear deformities, and it is often overlooked as a cause of hearing loss in children.

The involved vestibular aqueduct is usually markedly dilated and easily demonstrated on computed tomography (CT) (figure 1). Images obtained by magnetic resonance imaging (MRI) in multiple planes will show the actual content of the aqueduct and the dilated endolymphatic sac (figure 2). At present, we are unable to differentiate the signal of the endolymph seen in a large endolymphatic sac from perilymph and cerebrospinal fluid.

Reference

(1.) Swartz JD, Harnsberger HR. The otic capsule and otodystrophies. In: Swartz JD, Harnsberger HR (eds). Imaging of the Temporal Bone. New York: Thieme Medical Publishing, 1992:192-246