Transcanal infracochlear approach to the petrous apex.

Computerized tomography and magnetic resonance imaging have now made it possible to reliably differentiate cholesteatoma from cholesterol granuloma of the petrous apex. The treatment for cholesteatoma is complete surgical excision when possible, whereas cholesterol granuloma needs only adequate drainage for control. A new transcanal infracochlear approach for drainage of cholesterol granuloma involving the anterior petrous apex is described. Absolute measurements from 10 cadaveric temporal bones were obtained to determine the distances between the cochlea, jugular bulb, carotid artery, and facial nerve. In all specimens the petrous apex was entered without invading the cochlea, carotid, or jugular bulb. Advantages of this technique include a more direct route to the petrous apex, dependent drainage, and preservation of the normal hearing mechanism, including the tympanic membrane. Clinical indications for this technique include failure of other treatment approaches and a high jugular bulb obstructing an infralabyrinthine approach. Experience to date shows that patients experience little difficulty from the procedure.