Vestibular
Autorotation Test (VAT®)
was developed as a method of evaluating the vestibulo-ocular
reflex
(VOR)
.
* High frequency ( 2-6 Hz) VOR
test
( range of normal everyday locomotion )
* Active head rotation
* 18 second test
* Tests both the horizontal and vertical canals
* Comfortable
* Portable
* Report Writer
Diagnostic
Information
For
most of the population, balance control occurs at an
unconscious level. Signals from the inner ear
continuously drive the eye muscles to coordinate eye
movement with head movement. This coordination is
necessary to have clear vision and balance. The
communication between the ear and the eye is called
the vestibulo-ocular reflex (VOR). When the VOR is
functioning properly, eye speed and timing are equal
and opposite to those of the head. But, if the speed
or timing is off, even slightly, vision is distorted
because of apparent motion of the visual field.
The VAT® is an 18 second test of the high frequency
horizontal and vertical VOR’s for diagnosis,
treatment planning and monitoring of vestibular
disease. The frequency tested ( 2 - 6 Hz) closely
approximates normal head movements. For example, many
patients complain of dizziness or loss of balance when
they are walking, bending over or turning their head
quickly. The VAT® quickly and comfortably monitors a
patient’s head and eye motions to record what is
happening in the vestibular portion of the inner ear.
Testing with the VAT® often identifies problems not
found with other vestibular tests, because the VAT®
tests natural, faster motions and unlike other
conventional vestibular tests, evaluates both the
horizontal and vertical canals. Because the VAT® is
sensitive to changes of the VOR and is easy to
perform, it is often the first screening test a
patient receives who complain of dizziness or balance
problems. Patients do not object to repeated testing
which makes the VAT® the ideal test to monitor
ototoxic medication and vestibular rehabilitation.
The data shown below illustrates the VAT® test
results from a gentamicin ototoxicity patient. The
normative data is shown as the blue error bars ( ± 2
std.) Individual patient VAT® data are shown in
various colors. Notice that both the horizontal and
vertical gains (top two graphs) are well below the
normal data. The horizontal and vertical phases (
bottom two graphs) are above the normal data. This
data pattern is typically seen in gentamicin
ototoxicity.