Large vestibular aqueduct

Also known as widened vestibular aqueduct syndrome and enlarged endolymphatic sac
anomaly.

Clinical features:
Most common cause of SNHL in children/ teens
Gradual deterioration of HL
Usually bilateral
Sporadic
Associated with other cochlea malformations, like Mondini deformity, dilated vestibule and Pendred’s syndrome.

Anatomy:
Lies posterior and parallel to posterior semicircular canal
Joins labyrinth anteriorly at crus, enters extradural space of posterior cranial fossa on posterior
aspect of temporal bone.
Normally mid part of vestibular aqueduct measures less than 1.5 mm, and not bigger than posterior semicircular canal.
Contains endolymphatic sac
Axial images are used.

Imaging and pathology:
If > 1.5mm in the mid part; rule of thumb: if larger than P-SCC
No correlation between size and degree of hearing loss

CT:
Large vestibular aqueduct
Probably invariably a/w modilolar deficiency

MR:
Large Endolymphatic duct