How is positional testing in electronystagmography (ENG) performed?

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

Answer

The examiner places the patient in each position and evaluates him or her for a minimum of 20-30 seconds. Mental tasking is used to keep the patient from suppressing nystagmus. Visual suppression must also be avoided by the use of infrared goggles or with the patient’s eyes closed with electrodes. Some standard positions used include the following:

  • Head hanging

  • Supine

  • Supine, head right

  • Supine, head left

  • Lateral right

  • Lateral left

Many clinics do not assess in the lateral right and left positions unless nystagmus is observed in the supine position with the head to the right or left. The lateral right and left positions are used to rule out neck rotation as a cause for nystagmus.

Nonstandard positions include any position in which the patient reports dizziness (eg, dizziness when bending to tie shoes).

If no nystagmus is observed in any position, results are considered normal. For results to be considered abnormal, the nystagmus observed in positional testing should exceed 6 degrees per second, change direction in any 1 position, persist in at least 3 different positions, or be intermittent in all positions. Lesser degrees of nystagmus are of questionable pathologic significance.

If spontaneous nystagmus is observed, the nystagmus observed during positional testing must show an increase in velocity to be considered a significant positional finding.

Peripheral indicators include the following:

  • Direction-fixed nystagmus

  • Direction of nystagmus changing in different positions in a geotropic pattern (also consider a horizontal canal variant of BPPV in this case)

  • Latency of onset

  • Fatigability

Central indicators include the following:

  • The direction of nystagmus changing in different positions in an ageotropic pattern

  • The direction of nystagmus changing in a single position (a strong indicator for CNS pathology)

  • Immediate onset of nystagmus

  • Nonfatigability


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