Quote from PJMommy
Transphenoidal. You will see this approach done for certain pituitary tumors--that is, a transphenoidal hypophysectomy, meaning removal of the pituitary gland.
Now, if you have patients on your floor with acoustic neuromas, particularly medium-sized acoustic neuromas, you may also see a trans-labyrinthine approach--that is, from behind the ear, drilling through the mastoid and removing the inner ear structures. These operations, like transphenoidals, are generally done by a neurosurgeon and an ENT doc working as a team. I believe that this results in permanent deafness of that ear, but the other ear compensates for the hearing loss. The hole through the mastoid is usually patched with a fat graft taken from the patient's abdomen (autograft.)
Large acoustics require more extensive drilling through the mastoid; thus more bone removal.