Caloric testing assesses the function of which semicircular canal and vestibular nerve at very low frequencies by irrigating the ear with warm or cold air or water?

• A. Function of the anterior canal at high frequencies
• B. Function of the horizontal semicircular canal and vestibular nerve at very low frequencies by irrigating the ear with warm or cold air or water
• C. Function of the utricle at medium frequencies
• D. Cochlear function at low frequencies

Answer: (B)

Caloric testing targets the horizontal semicircular canal and the vestibular nerve, and it does so at very low frequencies by irrigating the ear with warm or cold air or water. The temperature difference creates convection currents in the endolymph of the horizontal canal, effectively stimulating that canal far below the frequency of natural head movements. Because the signal travels through the vestibular nerve to the brainstem, this test reveals how well that canal-nerve pathway is functioning. Warm irrigation excites the canal and tends to produce nystagmus toward the irrigated ear, while cold irrigation tends to produce nystagmus away from the irrigated ear. The anterior canal, utricle, and cochlea aren’t the primary targets of this test, since the utricle is an otolith organ and the cochlea governs hearing.