medicine Medicine is the science and practice of caring for a patient, managing the diagnosis, prognosis, prevention, treatment, palliation of their injury or disease, and promoting their health. Medicine encompasses a variety of health care pr ...

, the caloric reflex test (sometimes termed vestibular caloric stimulation) is a test of the vestibulo-ocular reflex that involves irrigating cold or warm water or air into the

external auditory canal The ear canal (external acoustic meatus, external auditory meatus, EAM) is a pathway running from the outer ear to the middle ear. The adult human ear canal extends from the pinna to the eardrum and is about in length and in diameter. Stru ...

. This method was developed by Robert Bárány, who won a

Nobel prize The Nobel Prizes ( ; sv, Nobelpriset ; no, Nobelprisen ) are five separate prizes that, according to Alfred Nobel's will of 1895, are awarded to "those who, during the preceding year, have conferred the greatest benefit to humankind." Alfr ...

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. 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 vestibular ...

(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 pain A phantom limb is the sensation that an amputated or missing limb is still attached. Approximately 80 to 100% of individuals with an amputation experience sensations in their amputated limb. However, only a small percentage will experience pai ...

s in

amputee Amputation is the removal of a limb 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 carried out on indiv ...

s and paraplegics. 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 observ ...

, hemianesthesia, and other consequences of right hemispheric damage.

Technique and results

Ice cold or warm water or air is irrigated into the

, 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. I ...

of the nearby lateral

semicircular canal In mathematics (and more specifically geometry), a semicircle is a one-dimensional locus of points that forms half of a circle. The full arc of a semicircle always measures 180° (equivalently, radians, or a half-turn). It has only one line o ...

. 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. Infants can be born with it but more commonly acquire it in infancy or later in life. In many cases it may result in reduced or limited vision. Due to the invol ...

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

ear, with horizontal nystagmus to the

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

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.

References

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

Utility

Technique and results

See also

References