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 pract ...

, 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. Struct ...

. This method was developed by

Robert Bárány Robert Bárány ( hu, Bárány Róbert, ; 22 April 1876 – 8 April 1936) was an Austrian-born otologist. He received the 1914 Nobel Prize in Physiology or Medicine for his work on the physiology and pathology of the vestibular apparatus. Life ...

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

. 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 vestibula ...

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

s in amputees 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 neural ...

s. It can also induce a temporary remission of

anosognosia Anosognosia is a condition in which a person with a disability is cognitively unaware of having it due to an underlying physical or psychological (e.g., PTSD, Stockholm syndrome, schizophrenia, bipolar disorder, dementia) condition. Anosognosia c ...

, 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 obser ...

, 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 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 of ...

. 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

eye Eyes are organs of the visual system. They provide living organisms with vision, the ability to receive and process visual detail, as well as enabling several photo response functions that are independent of vision. Eyes detect light and conv ...

s 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 pro ...

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.

References

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

Utility

Technique and results

See also

References