Electronystagmography is a test to look at voluntary and
involuntary eye movements . It evaluates the acoustic nerve,
which runs from the brain to the ears (and control hearing and
balance) and the occulomotor nerve, which runs from the brain to
the eyes. How the test is performed: Patches called electrodes
(similar to those used with ECG , but smaller) are placed above,
below, and to the side of each eye. They may be attached by
adhesive or by a band around the head. Another electrode is
attached to the forehead. The electrodes record eye movements
that occur when the inner ear and nearby nerves are stimulated
by delivering cold and warm water to the ear canal at different
times. Sometimes, the test is done using air instead of water.
Each ear is tested separately. When cold water enters the ear,
it should cause rapid, side-to-side eye movements called
nystagmus. The eyes should move rapidly away from the cold water
and slowly back. Next, warm water is placed into the ear. The
eyes should now move rapidly to