Electronystagmogram for vertigo
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.
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 examination.
Eye movements are smooth and precise while tracking a moving object. Nystagmus is not detected. Changes in head position do not bring on vertigo.
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.
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.
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 weakened.
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 interpret.
Because these tests cannot detect some inner ear problems, a normal result does not completely rule out an inner ear problem.
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