MedicsWhat is the caloric test (ice water in the ear)?
In The Iceman Cometh, a 1972 medical student is handed a bucket of ice water and told to find a brain tumor with it. Here's what the test actually does, and why the bucket was the least weird part.
The short answer
The caloric test checks the inner ear's balance system (the vestibular system) and its wiring through the brainstem. Warm or cold water, or air, is gently put into the ear canal. The temperature change stirs the fluid in the inner ear's balance canals, which normally makes the eyes flick in a characteristic pattern called nystagmus. Yes, doctors deliberately make you dizzy, and yes, it's diagnostic.
COWS, the only mnemonic that moos
Medical students learn which way the quick flick goes with COWS: Cold Opposite, Warm Same. Cold water in the left ear makes the fast phase beat toward the right; warm water makes it beat toward the left. Generations of students have mooed quietly during exams.
How it's used today
In balance clinics, caloric testing is part of videonystagmography (VNG) to find out whether dizziness comes from one inner ear. In a deeply unconscious patient, ice-water calorics test the brainstem reflex that connects the ears and eyes (the oculovestibular reflex), and the absence of that reflex is one part of a formal brain death examination.
A bit of history
Robert Bárány won the 1914 Nobel Prize in Physiology or Medicine for his work on the vestibular apparatus, including the caloric reaction. Before CT and MRI arrived in the 1970s and '80s, bedside neurological tests carried much more weight in finding disease. The elaborate eye-movement treasure map in The Iceman Cometh, however, is pure satire; please don't try to locate a tumor with a bucket.
Frequently asked questions
Does the caloric test hurt?
It isn't usually painful, but it's designed to cause brief dizziness and sometimes nausea, which pass within minutes. Think carnival ride, minus the funnel cake.
What does COWS stand for?
Cold Opposite, Warm Same: the direction of the fast phase of nystagmus relative to the ear being irrigated.
Can the caloric test find a brain tumor?
Not directly. It tests the vestibular system and brainstem pathways. Brain tumors are found with imaging such as MRI, not a bucket of ice water.
Hear it on the show
Not medical advice. This page is general information, written to explain terms our satire leans on; it isn't a substitute for advice from your own clinician. In an emergency, call 911.