In an electronystagmogram (ENG), wires (electrodes) attached to the
face detect involuntary eye movements (nystagmus) that
occur when a person has
vertigo. During this test, the person is asked to
track a moving object with the eyes, open and close the eyes, and change
positions of the head. These motions trigger vertigo for some people.
Near the end of the test, warm or cool water or air is gently
injected into each ear canal, one at a time. This is called a caloric test and
may be done without using electrodes to detect the eye movements.
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This test is done by a doctor in a hospital or clinic and usually
lasts about an hour.
Why It Is Done
The test often can help distinguish between inner ear (peripheral)
and brain (central) causes of vertigo. It usually is done only if the cause of
vertigo is not evident from the person's history and physical
Normal Eye movements are smooth and precise while tracking a
Nystagmus is not detected. Changes in head position do
not bring on vertigo.
Abnormal Eye movements are not smooth and precise while tracking a
moving object. Nystagmus and vertigo may occur only when the head is
stationary, or with changes in head position. When nystagmus is associated with
vertigo caused by an inner ear problem, the eyes repeatedly move rapidly in one
direction and then move back more slowly in the other direction. Nystagmus also
may occur with eye movement alone, suggesting a
central nervous system cause of vertigo.
Normal Involuntary eye movements in response to the caloric test
have normal direction and intensity. The caloric test may cause vertigo severe
enough to cause nausea.
Abnormal A lack of response or a diminished response to the
caloric test (no eye movements or vertigo, or less than expected) suggests that
the balance center in the inner ear is not functioning or is
What To Think About
These tests, especially the caloric test, can cause vertigo with
nausea and vomiting. These symptoms are temporary.
It is not normal to have warm or cold water injected into your ear.
Therefore, the caloric test causes an extreme situation that the ear would not
normally experience. In some cases, this can make the results difficult to
Because these tests cannot detect some inner ear problems, a normal
result does not completely rule out an inner ear problem.