The variational anatomy of the external aperture of the human vestibular aqueduct.

A study was undertaken to demonstrate the variational anatomy of the external aperture of the vestibular aqueduct in 90 human temporal bones obtained from 58 cadavers. Topographic landmarks of the posterior surface of the petrous bone are useful for general orientation and include the external aperture of the vestibular aqueduct, internal auditory meatus, sigmoid sinus, subarcuate fossa, superior petrosal sinus and cochlear canaliculus. We determined the mean distances from the external aperture of vestibular aqueduct to the above structures to be 10.98, 11.21, 9.42, 10.27 and 13.90 mm, respectively. Furthermore, the length of the external aperture of the vestibular aqueduct revealed significant differences between the right and left sides. The distances between the EAVA and certain anatomical structures on the posterior surface of the temporal bone should be taken into consideration during surgery. Knowing the variability of the position of the external aperture of the vestibular aqueduct may help surgeons avoid traumatizing, and thus producing inadvertent lesions to the hearing mechanism.