86
CALORIC TEST
Directional
Preponderance:
Nystagmus beats
stronger one way than
another.
Fixation Index: when
Nystagmus is at its
peak, the ratio of
velocity with no fixation
to velocity with fixation.
Unilateral weakness: of
more than 25% is
abnormal. Bilateral
weakness: sum of
velocities of all 4
irrigations
<20 º/sec
Directional
preponderance:
>25% difference.
Caloric weakness: is a
function of the
labyrinth or VIII cranial
nerve (vestibular
portion).
Unilateral: indicates
disabled side.
Bilateral: peripheral
organs,
Acute unilateral lesion
or perhaps CNS
(cerebellar).
Directional
preponderance: is not
localizing.
Videonystagmography is the most commonly used clinical test to evaluate
vestibular function, remember that the results of normal VNG tests do not
necessarily mean that a patient has a typical vestibular function. The
anomalies detected by VNG can be useful in the diagnosis and
localization of the site. Of the injury; however, many of the abnormalities
are not localized; therefore, the clinical history and otological examination of the
patient are of vital importance in the formulation of a diagnosis and treatment plan for
a patient with dizziness
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