During videonystagmography caloric testing, bithermal irrigations (30°C and 44°C) are performed. The peak slow-phase velocity of nystagmus induced by warm irrigation is approximately what percentage of that induced by cold irrigation on a normal ear?
- A Warm response is approximately 20-30% smaller than cold ✓
- B Warm response is approximately 20-30% greater than cold
- C Equal in magnitude
- D Cold irrigation does not elicit a response in normals
Correct answer: A. Warm response is approximately 20-30% smaller than cold
Explanation
Cold water produces a stronger caloric response than warm water on the same ear because the density gradient created by cooling is more effective at stimulating the semicircular canal. Warm responses are typically 20-30% smaller. This is the COWS convention (Cold Opposite, Warm Same). Cold always elicits a response in a functioning ear.
Reference: Handbook of Clinical Audiology, 7th ed.
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