What is the role of caloric reflex testing in the evaluation of acquired nystagmus?

Updated: Oct 17, 2018
  • Author: Christopher M Bardorf, MD, MS; Chief Editor: Edsel Ing, MD, MPH, FRCSC  more...
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Answer

Caloric testing

  • Instilling cold or warm water into the external auditory canal can reproduce the same movement of endolymph in the semicircular canals produced by rotations of the head. Instillation of water into the external auditory canal causes endolymph convection currents that in turn induce nystagmus.

  • While sitting erect, the patient tilts the head back 60°. While in supine, the patient elevates the head 30°; this brings the horizontal semicircular canals into the vertical plane.

  • The external auditory canal is irrigated with cold or hot water. Cold water instilled into the right ear causes the endolymph in the right semicircular canal to cool and sink. This movement of endolymph is the same movement induced by a rotation of the head to the left, inducing a horizontal nystagmus directed to the left (ie, to the opposite side the water was placed). Warm water in the same ear produces the opposite effect (ie, a horizontal nystagmus directed to the right or toward the same side the water was placed); ie, cold-opposite, warm-same (COWS).

Note whether the character of the nystagmus changes with otolithic stimulation. Failure to respond to otolithic stimuli implies peripheral vestibular disease.

A full neurologic examination may reveal the diagnosis. In patients with vertical pendular nystagmus, associated palatal undulation suggests oculopalatal myoclonus.

Visual acuity: In patients with latent nystagmus, acuity should be measured by fogging the contralateral eye with a hyperopic lens.


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