What is the typical caloric testing finding in unilateral vestibular hypofunction?

• A. Bilateral hyperfunction with increased responses on both sides
• B. Reduced or absent nystagmus and reduced responses on the affected side
• C. Normal caloric responses
• D. Increased nystagmus on the affected side

Answer: (B)

Caloric testing measures the function of the horizontal semicircular canals and the vestibulo-ocular reflex by provoking endolymph flow with warm or cold irrigation. When one labyrinth is hypofunctioning, its input to the reflex is reduced, so the response to caloric stimulation on that side is diminished. This shows up as reduced or absent nystagmus and overall reduced responses when testing the affected ear, creating a detectable unilateral weakness. The intact ear can still respond normally, but the asymmetry gives away the unilateral deficit.