Microsurgical anatomy of arteries related to the internal acoustic meatus.

The distribution and location of the labyrinthine arteries (LA) have been investigated in 6 adults and 15 human fetuses using microdissection. The LA is a single or double artery that penetrates the internal acoustic meatus (IAM) extending to the arachnoidal, dural, temporal and neural branches and ending at the fundus of the IAM in three terminal branches, namely the anterior vestibular artery (AVA), the vestibulocochlear artery (VCA) and the cochlear artery (CA). When the LA is a single artery, it is located on the cochlear nerve, under the facial nerve, and ends in the hiatus between the cochlear and the vestibular nerves. In cases with a biarterial system, the inferior LA passes under the nerves and becomes the VCA at the fundus of the IAM. The location of the superior LA is similar to that of the LA in the monoarterial system and the superior LA terminates at the cochlear artery and the VCA. The nomenclature, distribution and surgical importance of the two arterial patterns are analyzed.