Internal acoustic meatus

The internal acoustic meatus is a small bony canal that opens onto the posterior surface of the petrous part of the temporal bone, inside the posterior cranial fossa. It allows passage of the facial and vestibulocochlear nerves.

Shallow, it terminates in a fundus crossed by two crests, one more or less horizontal and the other vertical. 

These crests delimit four holes:

• the rostro-dorsal hole, the broader of these, through which the facial nerve passes (facial nerve area, or the endocranial orifice of the facial canal)

• the dorso-caudal hole (superior vestibular area)

• the ventro-caudal hole (inferior vestibular area)

• the rostro-ventral hole (cochlear area).

These last three holes have a cribriform appearance to allow passage of the corresponding branches of the vestibulocochlear nerve.