Vestibulo-Oculogyric Reflex (Caloric Reflex)

Vestibulo-oculogyric reflex (caloric reflex).

• To perform the vestibulo-oculogyric reflex, the supine patient is positioned so that his/her head is tilted upward 30 degrees.
• Inject cold water into the patient’s external ear canal, being sure to reach the tympanic membrane (anywhere from 3 ml up to 100 ml for this test)
• Watch the patient’s eyes for at least 1 minute after the cold-water injection.
• Wait at least 5 minutes before performing this same test on the opposite side.
• Interpretation.
• In a normal, alert patient, the patient’s eyes will slowly deviate toward the side of the cold-water injection and then quickly jerk back toward midline. If warm water is used, instead, the opposite response will be observed. The mnemonic COWS is used to remember this response; however, it refers to the direction of the nystagmus: Cold Opposite, Warm Same. Although memorable, this mnemonic is confusing because the test is most commonly done on comatose patients in whom this test does not produce nystagmus, only slow phase eye movements that (if normal) are in the same direction as the normal, alert individual.
• Complete vestibulo-ocular pathway dysfunction causes the eyes to fail to move in response to water injection.

Prior to performing the vestibulo-oculogyric reflex, use an otoscope to visualize the patient’s tympanic membranes and ensure they are intact.