The small cavity between the eardrum and inner ear conducts sound to the inner ear by three tiny bones called the malleus (the hammer), the incus (the anvil), and the stapes (the stirrup). The inner ear contains the cochlea (a coiled structure responsible for hearing), the semicircular canals (concerned with balance), and the vestible. The vestibule is an oval cavity that contains the saccule and utricle, which communicate with the cochlea and semicircular canals. The vestibular nerve passes impulses from the inner ear to the brain and is associated with balance; the cochlear nerve - part of the vestibular nerve - is associated with hearing.
Source: AMA's Current Procedural Terminology, Revised 1998 Edition. CPT is a trademark of the American Medical Association.