Has two branches
Cochlear – hearing
Vestibular – proprioception, understanding where the head
is in relation to gravity, tone to anti-gravity muscles, eye movements
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Assessment
1.
Cochlear
This is difficult to assess. A crude method is to make a loud,
startling sound (a clap), the patient should respond by turning
toward the sound, blinking, and moving the ears. Only bilateral
loss can be determined in this way, unilateral loss can be
missed. Unilateral dysfunction may be assessed only with the
use of a special hearing test, the brain stem evoked auditory
response (BAER).
2.
Vestibular
Physiological nystagmus, also called oculocephalic reflexes
or doll’s eye phenomena, is induced by turning the patient’s
head back (in a "yes" head movement) and moving
the head laterally and medially (in a "no" head
movement). The normal response to the oculocephalic test is
a quick movement of the eyeball in the direction of the head
travel.
Unilateral lesions usually result in nystagmus, ataxia, and
a head tilt toward the lesion.
