The caloric test stimulates which structure?

• A. The lateral semicircular canal
• B. The utricle
• C. The saccule
• D. The superior semicircular canal

Answer: (A)

Caloric testing works by creating a temperature-driven flow of endolymph that stimulates the hair cells in the semicircular canals. When the head is positioned so the horizontal (lateral) canal aligns with gravity, warm irrigation makes endolymph rise toward the ampulla and cool irrigation makes it fall away, deflecting the hair cells in the horizontal canal and producing a vestibulo-ocular reflex with nystagmus. The utricle and saccule are otolith organs that detect linear acceleration and head tilt, not rotational stimulation from caloric irrigation. The superior semicircular canal is not the primary focus of the standard caloric test, so the strongest, most consistent response comes from the lateral canal.