Calorics

Calorics, or caloric stimulation, are a vestibular function test used to evaluate the horizontal semicircular canals and the vestibulo-ocular pathways. By delivering temperature-contrast stimuli to the inner ear, calorics provoke endolymph flow that can produce nystagmus and vertigo in individuals with intact pathways. The test is a standard component of videonystagmography (VNG) or electronystagmography (ENG) assessments of unilateral vestibular function.

Mechanism and stimuli: The external auditory canal is irrigated with warm and cold water or air. Warm stimuli (approximately 44°C) excite the vestibular system on the irrigated side; cold stimuli (approximately 30°C) inhibit it. The resulting eye movements reflect the vestibular input imbalance and are most evident when the horizontal canal is aligned with gravity.

Procedure and interpretation: The head is raised about 30 degrees to align the horizontal canal with gravity. Each ear is stimulated with warm and cold stimuli for about 20–40 seconds. Eye movements are recorded; responses are quantified by slow-phase velocity. Calculations estimate canal paresis (unilateral weakness) and directional preponderance; the cold response typically beats away from the cold ear, warm toward the warm ear.

Clinical use and limitations: Calorics help distinguish peripheral from central vestibular disorders and are used in conditions such as vestibular neuritis and Menière’s disease. Results can be affected by age, tympanic membrane problems, canal plugging, and patient cooperation; central lesions may confound interpretation. It is one component of a broader vestibular assessment.

History: The caloric test was developed in the early 20th century by Robert Barány and remains a foundational vestibular test.