There was no middle ear dysfunction. It has long been recognised that there is an association between SNHL and enlarged vestibular aqueducts demonstrated on histological studies. The vestibular aqueduct is defined to be enlarged if it had a diameter greater than 1.5 mm. They also noted that this condition was relatively common in children with SNHL and was probably significantly underdiagnosed. The enlarged endolymphatic sac component, which prior to this could only be seen during surgery, was demonstrated radiologically for the first time.
Bilateral involvement is twice as common as unilateral involvement.
The bony vestibular aqueduct originates from the medial wall of the vestibule and extends dorsally for about 1 cm, opening on the dorsal surface of the petrous temporal bone within the posterior cranial fossa. During the fourth week of gestation, three buds are formed from the primordial otocyst. Two of the buds developed into the cochlea and semicircular canals respectively. The third bud develops into the endolymphatic duct system. Subsequently, the duct narrows, elongates, and assumes the typical J-shaped form of adult life.