To learn more about the different parts of the VNG, follow the links below:

Central (brain) tests
Positional testing
Caloric testing
Rotary chair
VEMP (vestibular evoked myogenic potential)

Rotary Chair

Below is a normal rotational chair tracing.  The three measures are gain (eye motion relative to head motion), symmetry (clockwise vs counterclockwise rotation) and phase measured over multiple frequencies.

Rotational (rotary) chair testing gives us information about the horizontal semicircular canal VOR (vestibulo-ocular response).  The VOR is what allows our eyes to make compensatory eye movements in response to head movements so that we may continue to focus on an object of interest.  When this response is not intact, blurring of vision and dizziness may occur with head movements.
The rotary chair adds accuracy to the VNG (videonystagmogram), the VNG having the potential for false positive and false negative results.  Rotary chair testing is especially useful in:

• Inconclusive or equivocal VNG results
  
• Bilateral vestibular loss
• Central compensation to a unilateral vestibular loss

Rotary chair is the gold standard test in diagnosing bilateral vestibular loss.

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Patient undergoing rotational chair testing.