How is caloric stimulation electronystagmography (ENG) performed?

Updated: Aug 06, 2019
  • Author: Angela G Shoup, PhD; Chief Editor: Arlen D Meyers, MD, MBA  more...
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Vestibular stimulators include water, air, and closed-loop cuff; water and air are commonly used. Water caloric irrigations provide a strong stimulus but cannot be used with patients with pressure equalization tubes or perforation of the tympanic membrane. Use of water as a stimulus should also be avoided in patients whose immune systems are compromised.

For caloric stimulation, the patient is placed in a reclining position with his or her head at a 30-degree angle. This position orients the lateral semicircular canals in the most vertical plane. Before recording responses to caloric stimulation, spontaneous nystagmus is evaluated in this position. Caloric stimulation can be accomplished with an alternating binaural bithermal, simultaneous binaural bithermal, or monothermal protocol. Simultaneous binaural bithermal protocols are not traditionally used clinically; thus, alternating binaural bithermal and monothermal protocols are discussed here.

In patients with responsive vestibular systems, caloric irrigation produces nystagmus in a predictable manner:

  • Cool irrigations: The fast phase of nystagmus beats in the direction opposite to the stimulated ear (ie, cool irrigation in the right ear causes left-beating nystagmus)

  • Warm irrigations: Nystagmus beats in the direction of the stimulated ear (ie, warm stimulation of the right ear produces right-beating nystagmus)

For a comparison of responses between ears, the test must be performed in exactly the same manner for each ear. Careful otoscopic examination allows the stimulus to be directed appropriately and at an equivalent depth in each ear canal. Furthermore, when using electrodes, recalibration is recommended prior to each irrigation to account for variations in corneal-retinal potential. [17]

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