Caloric testing primarily assesses which semicircular canal function and at what frequency?

• A. Anterior semicircular canal function at high frequency
• B. Posterior semicircular canal function at mid frequency
• C. Otolithic function at low frequency
• D. Horizontal semicircular canal function at low frequency

Answer: (D)

Caloric testing uses a temperature change in the ear to move the endolymph and deflect the cupula, which primarily stimulates the horizontal semicircular canal. In the usual setup, the endolymph movement is slow and sustained, so the test examines the vestibulo-ocular reflex at a very low frequency—about 0.003 Hz. This makes it a measure of how well the horizontal canal pathway drives eye movements when the head is relatively still. The otolith organs, which detect linear acceleration and tilt, aren’t the primary focus of caloric testing, and while the other canals can be affected to some degree, the caloric method is best understood as assessing horizontal canal function at low frequency.