How to perform the Caloric test

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The caloric test is a test of the lateral semicircular canals which identifies the degree to which the vestibular system is responsive and determines how symmetric the responses are, between left and right. The caloric test does not assess vertical canal function or otolithic function.

By using caloric irrigation, you are stimulating each end organ independently of the other to determine whether one end organ is weaker than the other (asymmetry) or whether neither end organ is providing enough vestibular information to the brain.

There is conflicting literature on whether you should ask patients to drop central nervous system suppressant medications for 48 hours before the VNG. Part of this debate is that patients often do not understand which medications are allowed and which are not.

A general rule of thumb is that the patient should stop taking medications that are prescribed for “dizziness” but continue to take other medications (such as heart medications, blood pressure medications, etc.).

A thorough examination of the external ear canal and tympanic membrane is necessary before the caloric test. The three most important factors to consider are:

The presence of a tympanic membrane (TM) perforation

The shape of the ear canal

If excessive cerumen is present, it might prevent the stimulus from reaching the inner-most part of the ear canal and could prohibit a reliable test result. Removal of even the smallest amounts of cerumen is beneficial to the testing process.