What is fixation suppression in caloric stimulation electronystagmography (ENG)?

Updated: Aug 06, 2019
  • Author: Angela G Shoup, PhD; Chief Editor: Arlen D Meyers, MD, MBA  more...
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Answer

Answer

After each caloric stimulus, the patient is instructed to fixate on a light or other stationary target. Fixation should normally eliminate or greatly reduce the induced nystagmus. If visual fixation does not inhibit nystagmus, central pathology at the level of the brain stem is indicated. The clinician must ensure that fixation suppression testing is completed as soon as the peak nystagmus response has been recorded. Fixation suppression testing is not accurate if the clinician waits to introduce the stimulus until the response has naturally decayed.

Compute the fixation index (FI):

FI = EO/EC,

where EO = nystagmus with eyes open (visual fixation) and EC = nystagmus with eyes closed (without visual fixation). An FI of 0.60 or greater is considered significant.


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