Active Head Rotation Testing

The VOR (vestibulo-ocular reflex) serves to stabilize our vision during movements in everyday life such as walking.  As our head turns either left to right or up and down the VOR keeps the world around us stable by applying automatic corrections to our eyes to compensate for the motion of our heads.  Very slow movements are controlled by the smooth pursuit system (movements under 2 Hz, i.e. cycles per second) while more rapid motions are controlled via the VOR system.  When this control mechanism becomes disturbed due to abnormalities of the peripheral or central vestibular system, a distorted picture of the environment becomes apparent to the patient with “slippage” of the visual image from the central vision creating what is termed as “oscillopsia” or a “bouncing” of the environment.

Traditional ENG or VNG testing has not been able to adequately test the VOR since the standard VNG battery uses only pursuit testing which tests the system at only a very low frequency of 2Hz or less.  This is also true of rotary chair testing.  The VAT or VORTEQ test is a very easy, accurate and efficient way to test the VOR system at higher frequencies (2-6Hz).  The test consists of placing a head band on the patient, which houses a small camera to record the direction and speed of eye movement and an accelerometer which measures the angle and speed of head movement. Then the patient is asked to move his or her head back and forth at increasing speed (for about 18 seconds) while staying focused on a spot on the wall which is placed about five feet in front of the patient.  The computer then analyses the data recorded as to the accuracy of the eye movements in terms of phase, speed and equality of left and right movements.  These data are then compared to standard normative data to evaluate individual patient results.  Certain patterns of abnormalities suggest either peripheral or central vestibular disorders.  Thus we now have an accurate and repeatable test of the VOR which is simple to administer for the examiner and simple to perform for the patient.

Howard Harris, M.S. FAAA

Audiologist

Sonus Hearing Care

1776 South Queen St.

York, PA  17403

howard.harris@amplifon.com