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Nystagmus can be clinically investigated by using a number of [[non-invasive (medical)|non-invasive]] standard tests. The simplest one is the [[caloric reflex test]], in which one [[ear canal]] is irrigated with warm or cold water or air. The temperature gradient provokes the stimulation of the [[horizontal semicircular canal]] and the consequent nystagmus. Nystagmus is often very commonly present with [[Chiari malformation]]. The resulting movement of the eyes may be recorded and quantified by a special device called an [[electronystagmograph]] (ENG), a form of [[electrooculography]] (an electrical method of measuring eye movements using external [[electrodes]]),<ref>{{cite journal | vauthors = Markley BA | title = Introduction to electronystagmography for END technologists | journal = American Journal of Electroneurodiagnostic Technology | volume = 47 | issue = 3 | pages = 178–89 | date = September 2007 | pmid = 17982846 | doi = 10.1080/1086508X.2007.11079629 | s2cid = 40334544 }}</ref> or an even less invasive device called a [[Videonystagmography|videonystagmograph]] (VNG),<ref>{{cite journal | vauthors = Mosca F, Sicignano S, Leone CA | title = Benign positional paroxysmal vertigo: videonystagmographic study using rotatory test | journal = Acta Otorhinolaryngologica Italica | volume = 23 | issue = 2 | pages = 67–72 | date = April 2003 | pmid = 14526552 |citeseerx=10.1.1.525.9140 }}</ref> a form of [[video-oculography]] (VOG) (a video-based method of measuring eye movements using external small cameras built into head masks), administered by an [[audiologist]]. Special swinging chairs with electrical controls can be used to induce rotatory nystagmus.<ref>{{cite journal | vauthors = Eggert T | title = Eye movement recordings: methods | journal = Developments in Ophthalmology | volume = 40 | pages = 15–34 | year = 2007 | pmid = 17314477 | doi = 10.1159/000100347 | isbn = 978-3-8055-8251-3 }}</ref> Over the past forty years, objective eye-movement-recording techniques have been applied to the study of nystagmus, and the results have led to greater accuracy of measurement and understanding of the condition. [[Orthoptist]]s may also use an [[optokinetic drum]], or [[electrooculography]] or [[Frenzel goggles]] to assess a patient's eye movements. Nystagmus can be caused by subsequent [[Foveal|foveation]] of moving objects, [[pathology]], sustained rotation or [[substance abuse|substance use]]. Nystagmus is not to be confused with other superficially similar-appearing disorders of eye movements ([[Saccade|saccadic]] oscillations) such as [[opsoclonus]] or [[ocular flutter]] that are composed purely of fast-phase (saccadic) eye movements, while nystagmus is characterized by the combination of a smooth pursuit, which usually acts to take the eye off the point of focus, interspersed with the saccadic movement that serves to bring the eye back on target. Without the use of objective recording techniques, it may be very difficult to distinguish among these conditions. In [[medicine]], the presence of nystagmus can be [[benign]], or it can indicate an underlying visual or [[neurology|neurological problem]].<ref name="pmid12438459">{{cite journal | vauthors = Serra A, Leigh RJ | title = Diagnostic value of nystagmus: spontaneous and induced ocular oscillations | journal = Journal of Neurology, Neurosurgery, and Psychiatry | volume = 73 | issue = 6 | pages = 615–8 | date = December 2002 | pmid = 12438459 | pmc = 1757336 | doi = 10.1136/jnnp.73.6.615 }}</ref> ===Pathological nystagmus=== Pathological nystagmus is characterized by "excessive drifts of stationary retinal images that degrades vision and may produce illusory motion of the seen world: oscillopsia (an exception is congenital nystagmus)".<ref name="Differences Between Physiologic and Pathologic Nystagmus">{{cite web|url=http://content.lib.utah.edu/cdm/ref/collection/EHSL-NOVEL/id/1855|title=Differences Between Physiologic and Pathologic Nystagmus|publisher=Spencer S. Eccles Health Sciences Library|access-date=22 November 2016}}</ref> Bechterew's phenomenon was discovered by [[Vladimir Bekhterev]] in 1883 in animal experiments.<ref>{{Cite journal |last=Bechterew |first=W. |date=December 1883 |title=Ergebnisse der Durchschneidung des N. acusticus, nebst Erörterung der Bedeutung der semicirculären Canäle für das Körpergleichgewicht |url=http://link.springer.com/10.1007/BF01674334 |journal=Pflüger, Archiv für die Gesammte Physiologie des Menschen und der Thiere |language=de |volume=30 |issue=1 |pages=312–347 |doi=10.1007/BF01674334 |issn=0031-6768}}</ref> Specifically, if one side of the vestibular system is damaged, then due to the lack of vestibular signal from that side, the animal behaves with nystagmus and vertigo. After a while, due to [[vestibular compensation]], nystagmus and vertigo stops. However, if then the other vestibular system is damaged, then nystagmus and vertigo occurs in the opposite direction. This is an early evidence of sensorimotor adaptation in the brain. It is rarely reported in humans.<ref>{{Cite journal |last1=Kim |first1=Yehree |last2=Jin |first2=Siyeon |last3=Kim |first3=Ji-Soo |last4=Koo |first4=Ja-Won |date=2022-03-28 |title=Bechterew's Phenomenon in Bilateral Sequential Vestibular Neuritis: A Report of Two Cases |journal=Frontiers in Neurology |volume=13 |pages=844676 |doi=10.3389/fneur.2022.844676 |doi-access=free |issn=1664-2295 |pmc=8996110 |pmid=35418928}}</ref> When nystagmus occurs without fulfilling its normal function, it is pathologic (deviating from the healthy or normal condition). Pathological nystagmus is the result of damage to one or more components of the [[vestibular system]], including the [[semicircular canal]]s, [[otolith]] organs, and the [[cerebellum|vestibulocerebellum]].{{contradict-inline|date=April 2014}} Pathological nystagmus generally causes a degree of [[vision impairment]], although the severity of such impairment varies widely. Also, many [[Blindness|blind]] people have nystagmus, which is one reason that some wear dark glasses.<ref>{{cite journal |title=Neurological Basis for Eye Movements of the Blind |date=2013 |journal=PLOS ONE |pmc=3575504 |volume=8 |issue=2 |pages=e56556 |doi=10.1371/journal.pone.0056556 |doi-access=free |pmid=23441203 |bibcode=2013PLoSO...856556S | vauthors = Schneider RM, Thurtell MJ, Eisele S, Lincoff N, Bala E, Leigh RJ }}</ref> ====Variations==== *'''Central nystagmus''' occurs as a result of either normal or abnormal processes not related to the vestibular organ. For example, lesions of the midbrain or cerebellum can result in up- and down-beat nystagmus. **'''Gaze induced nystagmus''' occurs or is exacerbated as a result of changing one's gaze toward or away from a particular side which has an affected central apparatus.<ref name="Godl_GEN&Rebound">{{cite web|url=https://collections.lib.utah.edu/ark:/87278/s6089dz6|title=Gaze-evoked and rebound nystagmus in a cerebellar syndrome| vauthors = Gold D |website=Neuro-Ophthalmology Virtual Education Library (NOVEL): Daniel Gold Collection|publisher=Spencer S. Eccles Health Sciences Library|access-date=9 September 2019|ref=Gold_GEN&Rebound}}</ref> *'''Peripheral nystagmus''' occurs as a result of either normal or diseased functional states of the vestibular system and may combine a rotational component with vertical or horizontal eye movements and may be ''spontaneous'', ''positional'', or ''evoked''. **'''Positional nystagmus''' occurs when a person's head is in a specific position.<ref name="pmid16705203">{{cite journal | vauthors = Anagnostou E, Mandellos D, Limbitaki G, Papadimitriou A, Anastasopoulos D | title = Positional nystagmus and vertigo due to a solitary brachium conjunctivum plaque | journal = Journal of Neurology, Neurosurgery, and Psychiatry | volume = 77 | issue = 6 | pages = 790–2 | date = June 2006 | pmid = 16705203 | pmc = 2077463 | doi = 10.1136/jnnp.2005.084624 }}</ref> An example of disease state in which this occurs is [[benign paroxysmal positional vertigo]] (BPPV). **'''Post rotational nystagmus''' occurs after an imbalance is created between a normal side and a diseased side by stimulation of the vestibular system by rapid shaking or rotation of the head. **'''Spontaneous nystagmus''' is nystagmus that occurs randomly, regardless of the position of the patient's head. ===Physiological nystagmus=== [[File:Lawrence 1960 13.8.png|thumb|right|A diagram of the [[caloric reflex test]], which tests the [[vestibulo-ocular reflex]] (VOR) by irrigating the ear canal with warm or cold water to induce physiological nystagmus.]] Physiological nystagmus is a form of involuntary [[Eye movement (sensory)|eye movement]] that is part of the [[vestibulo-ocular reflex]] (VOR), characterized by alternating [[smooth pursuit]] in one direction and [[saccadic movement]] in the other direction. ====Variations==== The direction of nystagmus is defined by the direction of its quick phase (e.g. a '''right-beating nystagmus''' is characterized by a rightward-moving quick phase, and a '''left-beating nystagmus''' by a leftward-moving quick phase). The [[oscillations]] may occur in the vertical,<ref name="pmid15872015">{{cite journal | vauthors = Pierrot-Deseilligny C, Milea D | title = Vertical nystagmus: clinical facts and hypotheses | journal = Brain | volume = 128 | issue = Pt 6 | pages = 1237–1246 | date = June 2005 | pmid = 15872015 | doi = 10.1093/brain/awh532 | doi-access = free }}</ref> horizontal or [[torsional]] planes, or in any combination. The resulting nystagmus is often named as a gross description of the movement, e.g. '''downbeat nystagmus''', '''upbeat nystagmus''', '''seesaw nystagmus''', '''periodic alternating nystagmus'''. These descriptive names can be misleading, however, as many were assigned historically, solely on the basis of subjective clinical examination, which is not sufficient to determine the eyes' true trajectory. * '''Optokinetic''' (''syn. ''opticokinetic) '''nystagmus''': a nystagmus induced by looking at moving visual stimuli, such as moving horizontal or vertical lines, and/or stripes. For example, if one fixates on a stripe of a rotating drum with alternating black and white, the gaze retreats to fixate on a new stripe as the drum moves. This is first a rotation with the same angular velocity, then returns in a [[saccade]] in the opposite direction. The process proceeds indefinitely. This is optokinetic nystagmus, and is a source for understanding the [[fixation reflex]].<ref>{{cite web |title=Testing for Optokinetic Nystigmus |url={{Google books|pEQhV88LTJYC|page=109|plainurl=y}} |pages=109–111 }} in {{cite book |doi=10.1016/B978-1-4377-1397-8.00008-3 |chapter=Examining the Visual System |title=Pediatric Clinical Skills |year=2011 | vauthors = Laroche GR |pages=101–121 |isbn=978-1-4377-1397-8 | veditors = Goldbloom RB }}</ref> * '''Postrotatory nystagmus''': if one spins in a chair continuously and stops suddenly, the fast phase of nystagmus is in the opposite direction of rotation, known as the "post-rotatory nystagmus", while slow phase is in the direction of rotation.<ref>{{cite journal | vauthors = Simón V, Llopis M, Bartual J | title = Physiological Postrotatory Nystagmus | journal = Applied Neurophysiology | volume = 38 | issue = 3 | pages = 161–171 | date = 1975 | pmid = 1232915 | doi = 10.1159/000102658 }}</ref> </textarea><div class="templatesUsed"></div><p id="mw-returnto">Return to <a href="/wiki/Nystagmus" title="Nystagmus">Nystagmus</a>.</p> <noscript><img src="https://login.wikimedia.org/wiki/Special:CentralAutoLogin/start?type=1x1&useformat=desktop" alt="" width="1" height="1" style="border: none; position: absolute;"></noscript> <div class="printfooter" data-nosnippet="">Retrieved from "<a dir="ltr" href="https://en.wikipedia.org/wiki/Nystagmus">https://en.wikipedia.org/wiki/Nystagmus</a>"</div></div> <div id="catlinks" class="catlinks catlinks-allhidden" data-mw="interface"></div> </div> </main> </div> <div class="mw-footer-container"> <footer id="footer" class="mw-footer" > <ul id="footer-info"> </ul> <ul id="footer-places"> <li id="footer-places-privacy"><a href="https://foundation.wikimedia.org/wiki/Special:MyLanguage/Policy:Privacy_policy">Privacy policy</a></li> <li id="footer-places-about"><a href="/wiki/Wikipedia:About">About Wikipedia</a></li> <li id="footer-places-disclaimers"><a href="/wiki/Wikipedia:General_disclaimer">Disclaimers</a></li> <li id="footer-places-contact"><a href="//en.wikipedia.org/wiki/Wikipedia:Contact_us">Contact Wikipedia</a></li> <li id="footer-places-wm-codeofconduct"><a href="https://foundation.wikimedia.org/wiki/Special:MyLanguage/Policy:Universal_Code_of_Conduct">Code of Conduct</a></li> <li id="footer-places-developers"><a href="https://developer.wikimedia.org">Developers</a></li> <li id="footer-places-statslink"><a href="https://stats.wikimedia.org/#/en.wikipedia.org">Statistics</a></li> <li id="footer-places-cookiestatement"><a href="https://foundation.wikimedia.org/wiki/Special:MyLanguage/Policy:Cookie_statement">Cookie statement</a></li> <li id="footer-places-mobileview"><a href="//en.m.wikipedia.org/w/index.php?title=Nystagmus&action=edit&section=9&mobileaction=toggle_view_mobile" class="noprint stopMobileRedirectToggle">Mobile view</a></li> </ul> <ul id="footer-icons" class="noprint"> <li id="footer-copyrightico"><a href="https://wikimediafoundation.org/" class="cdx-button cdx-button--fake-button cdx-button--size-large cdx-button--fake-button--enabled"><img src="/static/images/footer/wikimedia-button.svg" width="84" height="29" alt="Wikimedia Foundation" loading="lazy"></a></li> <li id="footer-poweredbyico"><a href="https://www.mediawiki.org/" class="cdx-button cdx-button--fake-button cdx-button--size-large cdx-button--fake-button--enabled"><img src="/w/resources/assets/poweredby_mediawiki.svg" alt="Powered by MediaWiki" width="88" height="31" loading="lazy"></a></li> </ul> </footer> </div> </div> </div> <div class="vector-settings" id="p-dock-bottom"> <ul></ul> </div><script>(RLQ=window.RLQ||[]).push(function(){mw.config.set({"wgHostname":"mw-web.codfw.canary-556c5f94cd-kvn2f","wgBackendResponseTime":250,"wgPageParseReport":{"limitreport":{"cputime":"0.065","walltime":"0.084","ppvisitednodes":{"value":418,"limit":1000000},"postexpandincludesize":{"value":17740,"limit":2097152},"templateargumentsize":{"value":6556,"limit":2097152},"expansiondepth":{"value":9,"limit":100},"expensivefunctioncount":{"value":0,"limit":500},"unstrip-depth":{"value":0,"limit":20},"unstrip-size":{"value":469,"limit":5000000},"entityaccesscount":{"value":0,"limit":400},"timingprofile":["100.00% 56.311 1 -total"," 99.84% 56.220 2 Template:Blocked_text"," 40.52% 22.820 2 Template:Replace"," 38.88% 21.893 1 Template:Colocationwebhost"," 35.32% 19.887 1 Template:Hidden"," 15.75% 8.871 1 Template:Hidden_begin"," 13.86% 7.802 1 Template:Tlx"," 2.47% 1.391 1 MediaWiki:Wikimedia-globalblocking-blockedtext-mistake"," 2.04% 1.150 1 MediaWiki:Wikimedia-globalblocking-blockedtext-mistake-email-steward"," 1.98% 1.116 1 Template:Hidden_end"]},"scribunto":{"limitreport-timeusage":{"value":"0.012","limit":"10.000"},"limitreport-memusage":{"value":1043262,"limit":52428800}},"cachereport":{"origin":"mw-web.codfw.canary-556c5f94cd-kvn2f","timestamp":"20241201011240","ttl":2592000,"transientcontent":false}}});});</script> </body> </html>