large vestibular aqueduct syndrome
Large vestibular aqueduct syndrome (LVAS), also known as enlarged vestibular aqueduct (EVA) or large endolymphatic sac anomaly (LESA), refers to the presence of congenital sensorineural hearing loss with an enlarged vestibular aqueduct due to enlargement of the endolymphatic duct. It is thought to be one of the most common congenital causes of sensorineural hearing loss.
Sensorineural hearing loss starts in childhood and is progressive . Hearing loss may be sudden onset and occurs after minor head trauma .
Associated anomalies are the norm, occurring in ~85% of patients :
- Pendred syndrome
- vestibular anomalies
- cochlear anomalies (e.g. cochlear hypoplasia, Mondini malformation, etc.)
- semicircular canal anomalies
A measurement of the vestibular aqueduct of 1.5 mm is considered the upper limit of normal . This measurement is ideally made halfway between the crus and the aperture on an axial view (i.e. AP dimension). Some studies suggest consideration of upper limit measurements of the midpoint of the aqueduct and operculum being at 1 mm and 2 mm, respectively .
The bony modiolus is not visible in up to 90% of cases.