Enlarged vestibular aqueduct

Enlarged vestibular aqueduct, also known as large vestibular aqueduct or large endolymphatic duct and sac syndrome or anomaly, is the most common inner ear malformation associated with sensorineural hearing loss.

Clinical presentation

The syndrome manifests as sensorineural or mixed hearing loss. Hearing may be normal at birth but typically manifests as fluctuating and/or progressive hearing loss in childhood ⁴. Hearing loss may be sudden onset, either spontaneously or after minor head trauma ⁶.

Pathology

Associations

Associated anomalies are the norm, occurring in ~85% of patients ⁶:

• Pendred syndrome ²
• vestibular anomalies
• cochlear anomalies (e.g. cochlear hypoplasia, Mondini malformation, etc.)
• semicircular canal anomalies

Radiographic features

CT/MRI

The classic (Valvassori) criterion for enlarged vestibular aqueduct is a diameter >1.5 mm at the midpoint ¹. The measurement is made halfway between the crus and the aperture on an axial view (i.e. AP dimension). This was originally established on polytomography and subsequently ported to CT as well as MRI ⁴.

The newer (Cincinnati) criteria for enlarged vestibular aqueduct are midpoint width ≥1.0 mm or opercular width ≥2.0 mm as measured in the axial plane ^3,5. When measured in the Pöschl plane, a vestibular aqueduct midpoint width of 0.9 mm is the upper limit of normal ⁷.

History and etymology

The clinical syndrome and imaging diagnosis was first described by Valvassori and Clemis in 1978 based on hypocycloidal polytomography ¹.