View source for Caloric reflex test

{{Short description|Test of the vestibulo-ocular reflex}}
{{cs1 config|name-list-style=vanc}}{{redirect|Nystagmus test|the field sobriety test|Horizontal gaze nystagmus test}}
{{Infobox diagnostic |
  Name        = Caloric reflex test, vestibulo-ocular reflex|
  Image       = File:Lawrence 1960 13.8.png|
  Caption     = '''Caloric test'''. '' Cold water introduced into right external meatus showing effects opposite to that produced by introduction of hot water. (Lawrence et al. 1960)''|
  Width       = 400px |
  ICD10       = |
  ICD9        = {{ICD9proc|95.44}} |
  MeshID      = |
  MedlinePlus = 003429 |
  OtherCodes  = |
}}
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]], 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]]. 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 pain]]s in [[amputee]]s<ref>{{cite journal |vauthors=André JM, Martinet N, Paysant J, Beis JM, Le Chapelain L |title=Temporary phantom limbs evoked by vestibular caloric stimulation in amputees |journal=Neuropsychiatry Neuropsychol Behav Neurol |volume=14 |issue=3 |pages=190–96 |year=2001 |pmid=11513103 }}</ref> and [[paraplegic]]s.<ref>{{cite journal |vauthors=Le Chapelain L, Beis JM, Paysant J, André JM |title=Vestibular caloric stimulation evokes phantom limb illusions in patients with paraplegia |journal=Spinal Cord |volume=39 |issue=2 |pages=85–87 |date=February 2001 |pmid=11402363 |doi=10.1038/sj.sc.3101093 |doi-access=free }}</ref> It can also induce a temporary remission of [[anosognosia]], the visual and personal aspects of [[hemispatial neglect]], [[hemianesthesia]], and other consequences of right hemispheric damage.<ref>{{cite book | last1 = Robertson | first1 = Ian H. | last2 = Marshall | first2 = John C. | title = Unilateral neglect: clinical and experimental studies | year = 1993 | pages = 111–113 | publisher = Psychology Press | url = https://books.google.com/books?id=fA2Em0VSUwAC&pg=PA111 | accessdate = 2010-06-04 | isbn = 978-0-86377-208-5}}</ref>

==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]] of the nearby lateral [[semicircular canal]]. Hot and cold water produce currents in opposite directions and therefore a horizontal [[nystagmus]] in opposite directions.<ref name="Cold caloric test">{{cite book | title=Neuroscience| last=Purves| first=D| year=2004| publisher=Sinauer|display-authors=et al}}</ref>
In patients with an intact brainstem: 
*If the water is warm (44&nbsp;°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 [[Eye|eyes]] will turn toward the [[contralateral]] ear, with horizontal [[Pathologic nystagmus|nystagmus]] (quick horizontal eye movements) to the [[ipsilateral]] ear.
*If the water is cold, relative to [[body temperature]] (30&nbsp;°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.<ref>{{EMedicine|oph|339|Nystagmus, Acquired}}</ref><ref name=narenthiran>Narenthiran G. [http://www.annals-neurosurgery.org/quiz/nsq2/#a3 Neurosurgery Quiz.] Annals of Neurosurgery. Accessed on: August 17, 2006.</ref>

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.<ref>{{cite journal |vauthors=Mueller-Jensen A, Neunzig HP, Emskötter T |title=Outcome prediction in comatose patients: significance of reflex eye movement analysis |journal=J. Neurol. Neurosurg. Psychiatry |volume=50 |issue=4 |pages=389–92 |date=April 1987 |pmid=3585347 |pmc=1031870 |doi=10.1136/jnnp.50.4.389 }}</ref>

While large interindividual differences exist, females exhibit a slightly higher average caloric excitability than males.<ref name="DOI10.1111/nyas.15310">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 {{DOI|10.1111/nyas.15310}}.</ref>

==See also==
* [[Balance disorder]]
* [[Inner ear]]

==References==
{{reflist|2}}

{{Operations and other procedures on the ear}}

[[Category:Physical examination]]
[[Category:Ear procedures]]
[[Category:Medical mnemonics]]