A test that stimulates each vestibular labyrinth independently by irrigating the ear canal with warm and cool water or air, then measuring the eye movement response. The most reliable way to detect a unilateral vestibular weakness.
Medical definition
The caloric test exploits the fact that temperature changes in the ear canal create convection currents in the endolymph of the horizontal semicircular canal, mimicking the effect of head rotation. With the patient lying supine and the head tilted 30 degrees (to align the horizontal canal vertically), warm irrigation (44 degrees C) induces nystagmus beating toward the irrigated ear; cool irrigation (30 degrees C) induces nystagmus beating away. The mnemonic COWS — Cold Opposite, Warm Same — describes the direction. By comparing the responses from each ear, the test can quantify the degree of vestibular weakness in percentage terms. A canal paresis of more than 25% on one side indicates a significant unilateral peripheral deficit. The test is performed as part of VNG and takes approximately 20 to 30 minutes of the total testing session.
Why it matters for vertigo
The caloric test is the only bedside or office test that can assess each labyrinth in isolation. It is essential for diagnosing vestibular neuritis (reduced or absent caloric response on the affected side), Meniere’s disease (variable caloric responses during different stages), and acoustic neuroma (progressive unilateral caloric weakness). It is also used to document recovery — comparing canal paresis before and after vestibular rehabilitation gives an objective measure of compensation. Without a caloric test, a “normal” VNG does not fully rule out unilateral peripheral hypofunction.
Where I see this in clinic
At Prime ENT Center in Hardoi, the caloric test is part of every full VNG workup. It is particularly useful when a patient presents with months of residual dizziness after a presumed vestibular neuritis episode. The caloric result tells me how much function the affected ear has recovered. If canal paresis remains above 35 to 40%, I push strongly for vestibular rehabilitation rather than medication, because the brain is still compensating for a real peripheral deficit. When caloric responses are symmetric and normal, the dizziness is more likely central or functional in origin.
Related terms
VNG — the full test battery that includes the caloric test. Nystagmus — the eye movement the caloric test measures. Vestibular neuritis — the condition most reliably identified by an asymmetric caloric result. Endolymph — the fluid whose thermal convection drives the caloric response.
Medical Disclaimer: This glossary entry is for educational purposes only. Consult Dr. Prateek Porwal directly. WhatsApp: 7393062200.