What is the rationale behind caloric testing in vestibular assessment?

What is the rationale behind caloric testing in vestibular assessment?

• A. Stimulates utricle
• B. Stimulates saccule
• C. Causes endolymph movement in the lateral semicircular canal
• D. Stimulates the cochlea

Answer: (C)

Caloric testing assesses the vestibular system by provoking endolymph movement in the horizontal semicircular canal through thermal convection. When the head is positioned to align this canal with gravity, irrigating warm or cold water creates currents in the endolymph. These currents deflect the hair cells in the lateral canal, altering vestibular nerve firing and producing a vestibulo-ocular response (nystagmus) that reveals canal function and any asymmetry between sides. This is why the rationale is that caloric stimulation moves endolymph specifically in the lateral semicircular canal. Otolith organs like the utricle and saccule respond to linear acceleration and gravity and are not the primary targets of caloric irrigation; the cochlea is related to hearing, not the vestibular response measured here.

Caloric testing assesses the vestibular system by provoking endolymph movement in the horizontal semicircular canal through thermal convection. When the head is positioned to align this canal with gravity, irrigating warm or cold water creates currents in the endolymph. These currents deflect the hair cells in the lateral canal, altering vestibular nerve firing and producing a vestibulo-ocular response (nystagmus) that reveals canal function and any asymmetry between sides. This is why the rationale is that caloric stimulation moves endolymph specifically in the lateral semicircular canal. Otolith organs like the utricle and saccule respond to linear acceleration and gravity and are not the primary targets of caloric irrigation; the cochlea is related to hearing, not the vestibular response measured here.