In medicine, 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. 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 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 (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 pains 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, hemianesthesia, and other consequences of right hemispheric damage.

Technique and results

Ice cold or warm water or air is irrigated 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 of the nearby lateral semicircular canal. Hot and cold water produce currents in opposite directions and therefore a horizontal nystagmus 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 nystagmus (quick horizontal eye movements) to the ipsilateral ear. *If the water is cold, relative to body 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 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