The Vestibulocochlear (Acoustic) Nerve

The VIIIth cranial nerve is actually composed of two functionally different components, the vestibular nerve and the cochlear nerve; it is thus preferentially referred to as the vestibulocochlear nerve – the nerve of equilibrium and hearing. Each component primarily conducts impulses centrally from the organs of equilibrium and hearing within the inner ear. The vestibular nerve conducts impulses from the cristae of the semicircular ducts and from the maculae of the utricule and saccule. The cell bodies of the afferent fibers of the cochlear nerve are cells that comprise the spiral ganglion. This is situated in the long spiral canal of the cochlea. This chapter briefly discusses some basic tests to assess the clinical status of the vestibular and acoustic systems, including the integrity of the VIIIth nerve. It discusses clinical issues that primarily are thought to involve the nerve rather than the inner ear mechanisms.