medicine Medicine is the science and Praxis (process), practice of caring for patients, managing the Medical diagnosis, diagnosis, prognosis, Preventive medicine, prevention, therapy, treatment, Palliative care, palliation of their injury or disease, ...

, the caloric reflex test (sometimes termed vestibular caloric stimulation) is a test of the

vestibulo-ocular reflex The vestibulo-ocular reflex (VOR) is a reflex that acts to stabilize Gaze (physiology), gaze during head movement, with eye movement due to activation of the vestibular system, it is also known as the cervico-ocular reflex. The reflex acts to im ...

that involves irrigating cold or warm water or air into the external auditory canal. This method was developed by Robert Bárány, who won a

Nobel Prize The Nobel Prizes ( ; ; ) are awards administered by the Nobel Foundation and granted in accordance with the principle of "for the greatest benefit to humankind". The prizes were first awarded in 1901, marking the fifth anniversary of Alfred N ...

in 1914 for this discovery.

Utility

The test is commonly used by physicians, audiologists and other trained professionals to validate a diagnosis of asymmetric function in the peripheral

vestibular system The vestibular system, in vertebrates, is a sensory system that creates the sense of balance and spatial orientation for the purpose of coordinating motor coordination, movement with balance. Together with the cochlea, a part of the auditory sys ...

. Calorics are usually a subtest of the

electronystagmography Electronystagmography (ENG) is a diagnostic test to record involuntary movements of the eye caused by a condition known as nystagmus. It can also be used to diagnose the cause of vertigo, dizziness or balance dysfunction by testing the vestibul ...

(ENG) battery of tests. It is one of several tests which can be used to test for

brain stem The brainstem (or brain stem) is the posterior stalk-like part of the brain that connects the cerebrum with the spinal cord. In the human brain the brainstem is composed of the midbrain, the pons, and the medulla oblongata. The midbrain is co ...

death. One novel use of this test has been to provide temporary pain relief from phantom limb pains in

amputee Amputation is the removal of a limb or other body part by trauma, medical illness, or surgery. As a surgical measure, it is used to control pain or a disease process in the affected limb, such as malignancy or gangrene. In some cases, it is ...

s and

paraplegic Paraplegia, or paraparesis, is an impairment in motor or sensory function of the lower extremities. The word comes from Ionic Greek () "half-stricken". It is usually caused by spinal cord injury or a congenital condition that affects the neura ...

s. It can also induce a temporary remission of anosognosia, the visual and personal aspects of

hemispatial neglect Hemispatial neglect is a neuropsychological condition in which, after damage to one hemisphere of the brain (e.g. after a stroke), a deficit in attention and awareness towards the side of space opposite brain damage (contralesional space) is obs ...

, hemianesthesia, and other consequences of right hemispheric damage.

Technique and results

Ice cold or warm water or air is introduced into the external auditory canal, usually using a syringe. The temperature difference between the body and the injected water creates a convective current in the

endolymph Endolymph is the fluid contained in the membranous labyrinth of the inner ear. The major cation in endolymph is potassium, with the values of sodium and potassium concentration in the endolymph being 0.91 mM and 154 mM, respectively. ...

of the nearby lateral

semicircular canal The semicircular canals are three semicircular interconnected tubes located in the innermost part of each ear, the inner ear. The three canals are the lateral, anterior and posterior semicircular canals. They are the part of the bony labyrinth, ...

. Hot and cold water produce currents in opposite directions and therefore a horizontal

nystagmus Nystagmus is a condition of involuntary (or voluntary, in some cases) Eye movement (sensory), eye movement. People can be born with it but more commonly acquire it in infancy or later in life. In many cases it may result in visual impairment, re ...

in opposite directions. In patients with an intact brainstem: *If the water is warm (44 °C or above) endolymph in the ipsilateral horizontal canal rises, causing an increased rate of firing in the vestibular afferent nerve. This situation mimics a head turn to the ipsilateral side. Both

eyes An eye is a sensory organ that allows an organism to perceive visual information. It detects light and converts it into electro-chemical impulses in neurons (neurones). It is part of an organism's visual system. In higher organisms, the ey ...

will turn toward the

contralateral Standard anatomical terms of location are used to describe unambiguously the anatomy of humans and other animals. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position prov ...

ear, with horizontal

(quick horizontal eye movements) to the ipsilateral ear. *If the water is cold, relative to

body temperature Thermoregulation is the ability of an organism to keep its body temperature within certain boundaries, even when the surrounding temperature is very different. A thermoconforming organism, by contrast, simply adopts the surrounding temperature ...

(30 °C or below), the endolymph falls within the semicircular canal, decreasing the rate of vestibular afferent firing. This situation mimics a head turn to the contralateral side. The eyes then turn toward the ipsilateral ear, with horizontal nystagmus to the contralateral ear.Narenthiran G
Neurosurgery Quiz.
Annals of Neurosurgery. Accessed on: August 17, 2006. Absent reactive eye movement suggests vestibular weakness of the horizontal semicircular canal of the side being stimulated. In comatose patients with cerebral damage, the fast phase of nystagmus will be absent as this is controlled by the cerebrum. As a result, using cold water irrigation will result in deviation of the eyes toward the ear being irrigated. If both phases are absent, this suggests the patient's brainstem reflexes are also damaged and carries a very poor prognosis. While large interindividual differences exist, females exhibit a slightly higher average caloric excitability than males.J. Gerb, Sandra Becker‐Bense, Doreen Huppert, Konstanze Dunker, Valerie Schöb, Denis Grabova, Karoline Steinmetz, Ralf Strobl, Andreas Zwergal: ''Sex differences in caloric nystagmus intensity: Should reference values be updated?.'' In: ''PubMed.'' 2025 .

References

{{Operations and other procedures on the ear Physical examination Ear procedures Medical mnemonics

Utility

Technique and results

See also

References