Correct. This is the vestibular aqueduct, in this case normal in size. Enlarged vestibular aqueduct syndrome (EVAS) is associated with congenital sensorineural hearing loss. To a first approximation, the vestibular aqueduct should not be wider in than the mid-portion than the adjacent semicircular canals (or about 1.5 mm), but note that the posterior aperture can normally fan out. The condition can be bilateral and can be associated with Mondini malformation (and some other inner ear malformations).