FIG 5. Illustration of the perilymphatic labyrinthine space, the fissula ante fenestram (label underlined) and fossula post fenestram (adapted from [8], permission pending). The endolymphatic spaces within the semicircular canals and cochlear duct are drawn as grooves in the perilymphatic surface. The outer surface of the perilymphatic space conforms to the bony labyrinth. The fissula ante fenestram arises from the lateral wall of the vestibule and nearby scala vestibulae, and it continues parallel to the adjacent cochlear turn.