View source for Pathologic nystagmus

{{Merge from|physiologic nystagmus|date=May 2010}}
{{SignSymptom infobox |
  Name           = Nystagmus |
  Image          = Optokinetic nystagmus.gif|
  Caption        = Horizontal [[optokinetic nystagmus]], a normal ([[physiological]]) form of nystagmus.|
  DiseasesDB     = 23470 |
  ICD10          = {{ICD10|H|55||h|55}}, {{ICD10|H|81.4||h|80}} |
  ICD9           = {{ICD9|379.50}}, {{ICD9|794.14}} |
  ICDO           = |
  OMIM           = |
  MedlinePlus    = |
  eMedicineSubj  = |
  eMedicineTopic = |
  MeshID         = D009759 |
}}
'''Pathologic nystagmus''' is a form of involuntary [[Eye movement (sensory)|eye movement]]. It is characterized by alternating [[smooth pursuit]] in one direction and [[saccadic movement]] in the other direction.

When nystagmus occurs without filling 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]].

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 web |url=http://www.drhull.com/EncyMaster/N/nystagmus.html |title=nystagmus |accessdate = 2007-06-07 |work=}}</ref>

==Prevalence==
Nystagmus is a relatively common clinical condition, affecting one in every 5,000 to 10,000 individuals.{{Citation needed|date=February 2007}} One survey in Oxfordshire, England, reported that one in every 670 children has manifesting nystagmus by the age of two.<ref>{{cite web |url=http://www.nystagmus.org/aboutn.html |title=American Nystagmus Network-About Nystagmus |accessdate = 2007-06-07 |work=}}</ref> Authors of another study in the United Kingdom estimated an incidence of 24 in 10,000, noting an apparently higher rate amongst white Europeans than in individuals of Asian origin.<ref>{{Cite pmid|19458336}}</ref>

==Variations==
*'''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 |author=Anagnostou E, Mandellos D, Limbitaki G, Papadimitriou A, Anastasopoulos D |title=Positional nystagmus and vertigo due to a solitary brachium conjunctivum plaque |journal=J. Neurol. Neurosurg. Psychiatr. |volume=77 |issue=6 |pages=790–2 |year=2006 |month=June |pmid=16705203 |doi=10.1136/jnnp.2005.084624 |url=http://jnnp.bmj.com/cgi/pmidlookup?view=long&pmid=16705203 |pmc=2077463}}</ref>  An example of disease state in which this occurs is [[Benign paroxysmal positional vertigo]] (BPPV).
**'''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 vestibular apparatus.
**'''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.
*'''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.

==Causes==
The cause for pathological nystagmus may be [[congenital]], [[idiopathic]], or secondary to a pre-existing [[neurological disorder]]. It also may be induced temporarily by disorientation (such as on roller coaster rides) or by certain [[psychoactive drug|drug]]s ([[alcohol]] and other [[central nervous system]] depressants, inhalant drugs, and the dis-associative anesthetics [PCP]).
===Congenital===
Congenital nystagmus occurs more frequently than acquired nystagmus.  It can be insular or accompany other disorders (such as micro-ophthalmic anomalies or [[Down's Syndrome]]).  Congenital nystagmus itself is usually mild and non-progressive. The affected persons are not normally aware of their spontaneous eye movements, but vision can be impaired depending on the severity of the movements.

Types of congenital nystagmus include the following:
*Infantile:
:*[[Idiopathic]]
:*[[Albinism]]
:*[[Aniridia]]
:*[[Leber's congenital amaurosis]]
:*Bilateral [[optic nerve hypoplasia]]
:*Bilateral congenital [[cataracts]]
:*[[Rod monochromatism]]
:*[[Optic nerve]] or [[macula]]r disease
:*[[Persistent tunica vasculosa lentis]]
:* Visuo-motor syndrome of functional monophthalmos
*[[Noonan syndrome]]
*Latent nystagmus
*Nystagmus blockage syndrome

X-linked infantile nystagmus is associated with mutations of the gene [[FRMD7]], which is located on the [[X chromosome]].<ref>{{Cite pmid|18161616}}</ref><ref name="pmid18431453">{{cite journal |author=Li N, Wang L, Cui L, ''et al.'' |title=Five novel mutations of the FRMD7 gene in Chinese families with X-linked infantile nystagmus |journal=Mol. Vis. |volume=14 |issue= |pages=733–8 |year=2008 |pmid=18431453 |doi= |url= |pmc=2324116}}</ref>

Congenital nystagmus is also associated with two X-linked eye diseases known as complete congenital stationary night blindness (CSNB) and incomplete CSNB (iCSNB or CSNB-2), which are caused by mutations of one of two genes located on the X chromosome. In CSNB, mutations are found in NYX (nyctalopin).<ref>{{Cite pmid|16157331}}</ref><ref>{{Cite pmid|18617546}}</ref> CSNB-2 involves mutations of CACNA1F, a [[voltage-gated calcium channel]] that, when mutated, does not conduct ions.<ref>{{Cite pmid|17949918}}</ref>

===Acquired===
====Diseases====
Some of the diseases that present nystagmus as a pathological sign:
*[[Benign Paroxysmal Positional Vertigo]] <ref name="pmid16878247">{{cite journal |author=Dorigueto RS, Ganança MM, Ganança FF |title=The number of procedures required to eliminate positioning nystagmus in benign paroxysmal positional vertigo |journal=Rev Bras Otorrinolaringol (Engl Ed) |volume=71 |issue=6 |pages=769–75 |year=2005 |pmid=16878247 |doi= |url=http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0034-72992005000600014&lng=en&nrm=iso&tlng=en}}</ref>
*[[Head trauma]]
*[[Stroke]] (the most common cause in older people)
*[[Ménière's disease]] and other [[balance disorder]]s
*[[Multiple sclerosis]]
*[[Brain tumor]]s ([[Medulloblastoma]], [[Astrocytoma]], or other tumors in the [[posterior fossa]].
*[[Wernicke-Korsakoff syndrome]]
*[[Encephalopathy]]
*[[Lateral medullary syndrome]]
*[[Aniridia]]
*[[Optic nerve hypoplasia]]
*[[Albinism]]
*[[Pelizaeus-Merzbacher disease]]
*[[Superior canal dehiscence syndrome]]
*[[Tullio phenomenon]]
*[[Horner's Syndrome]]
*[[Whipple's disease]]

====Toxic/metabolic====
Nystagmus from toxic or metabolic reasons could be the result of the following:
*Alcohol intoxication
*[[Lithium pharmacology|Lithium]]
*[[Barbiturates]]
*[[Selective serotonin reuptake inhibitor|SSRIs]]
*[[Phenytoin]] (Dilantin)
*[[Salicylates]]
*[[Benzodiazepines]]
*[[Lysergic acid diethylamide]] (LSD)
*[[Phencyclidine]] (PCP)
*[[Ketamine]]
*Other anticonvulsants or sedatives
*[[Methylenedioxymethamphetamine]]
*[[Wernicke's encephalopathy]]
*[[Thiamine]] deficiency

====Central nervous system disorders====
If the pathologic nystagmus is based in the [[central nervous system]] (CNS), such as with a [[cerebellum|cerebellar]] problem, the nystagmus can be in any direction ''including'' horizontal. Purely vertical nystagmus is usually central in origin.

Causes include e.g.:
*[[Thalamus|Thalamic]] hemorrhage
*[[Tumor]]
*[[Stroke]]
*Trauma
*[[Multiple sclerosis]]
*[[Cerebellar ataxia]]
*[[Brain_zaps#.22Brain_zaps.22_and_.22electric_shock_sensations.22|Withdrawal from certain antidepressants]]<ref>Christmas, David M. B. "‘Brain shivers’: from chat room to clinic ". The Psychiatrist (2005) 29: 219-221. doi: 10.1192/pb.29.6.219</ref>

====Other causes====
*Vestibular Pathology ([[Ménière's disease]], SCDS ([[superior canal dehiscence syndrome]]), [[BPPV]], [[Labyrinthitis]])
*[[Trochlear nerve]] malfunction<ref name=Lindgren>{{cite book|
title=Kliniska färdigheter: Informationsutbytet mellan patient och läkare
|last=Lindgren|first=Stefan|isbn=91-44-37271-X|language=Swedish
|location=Lund|publisher=Studentlitteratur|year=1993|
unused_data=ISBN status=May be invalid - please double check}}</ref>
*Non-physiologic

==Diagnosis==
Nystagmus is very noticeable but little recognized. Nystagmus can be clinically investigated by using a number of [[non-invasive (medical)|non-invasive]] standard tests. The simplest one is [[Caloric reflex test]], in which one [[ear|external auditory meatus]] is irrigated with warm or cold water. The temperature gradient provokes the stimulation of the [[vestibulocochlear nerve]] and the consequent nystagmus.

The resulting movement of the eyes may be recorded and quantified by special devices called [[electronystagmograph]] (ENG), a form of [[electrooculography]] (an electrical method of measuring eye movements using external [[electrodes]]),<ref>{{Cite pmid|17982846}}</ref> or even less invasive devices called [[videonystagmograph]] (VNG),<ref>{{Cite pmid|14526552}}</ref> a form of [[video-oculography]] (VOG) (a video-based method of measuring eye movements using external small cameras built into head masks) by an [[audiologist]]. Special swinging chairs with electrical controls are also used in this test to induce rotatory nystagmus.<ref>{{Cite pmid|17314477}}</ref>

==Treatment==
Congenital nystagmus has traditionally been viewed as non-treatable, but medications have been discovered in recent years that show promise in some patients.  In 1980, researchers discovered that a drug called [[baclofen]] could effectively stop periodic alternating nystagmus.  Subsequently, [[gabapentin]], an anticonvulsant, was found to cause improvement in about half the patients who received it to relieve symptoms of nystagmus. Other drugs found to be effective against nystagmus in some patients include [[memantine]]<ref>Memantine/Gabapentin for the treatment of congenital nystagmus. [http://www.ncbi.nlm.nih.gov/pubmed/17764629 PMID: 17764629]</ref>, [[levetiracetam]], 3,4-diaminopyridine, [[4-Aminopyridine|4-aminopyridine]], and [[acetazolamide]].<ref name=Groves2006>Groves, Nancy.

Many options to treat nystagmus, more in development. ''Ophthalmology Times'', March 15, 2006. [http://www.ophthalmologytimes.com/ophthalmologytimes/article/articleDetail.jsp?id=313686&ref=25]</ref> Several therapeutic approaches, such as [[contact lenses]],<ref name="pmid14742616">{{cite journal |author=Biousse V, Tusa RJ, Russell B, ''et al.'' |title=The use of contact lenses to treat visually symptomatic congenital nystagmus |journal=J. Neurol. Neurosurg. Psychiatr. |volume=75 |issue=2 |pages=314–6 |year=2004 |month=February |pmid=14742616 |doi= 10.1136/jnnp.2003.010678|url=http://jnnp.bmj.com/cgi/pmidlookup?view=long&pmid=14742616 |pmc=1738913}}</ref> drugs, [[surgery]], and [[low vision]] [[Rehabilitation (neuropsychology)|rehabilitation]] have also been proposed.

Clinical trials of a surgery to treat nystagmus (known as tenotomy) concluded in 2001. Tenotomy is being performed regularly at the University of Pittsburgh Children's Hospital and by a handful of surgeons around the world. The surgery developed by Louis F. Dell'Osso Ph.D aims to reduce the eye shaking (oscillations), which in turn tends to improve visual acuity.

==Research==

Several universities are researching nystagmus and are looking for volunteers to take part in research activities.

[http://www.nystagmusnet.org/Research.htm Current UK Research Projects]

==See also==
* [[Opsoclonus]]
* [[Optokinetic nystagmus]]
* [[Orthoptist]]
* [[Physiologic nystagmus]]

==References==
{{Reflist}}

==External links==
{{Wiktionary|Nystagmus}}
* [http://www.nystagmus.org American Nystagmus Network] &mdash; US-based support organisation
* [http://www.nystagmusnet.org Nystagmus Network UK] &mdash; UK-based support organisation
* [http://www.nystagmus.co.uk nystagmus.co.uk] &mdash; a teenager's experiences of nystagmus and a friendly forum
* [http://www.theshiftyeyesblog.com The Shifty Eyes Blog] &mdash; a blog about life with nystagmus
* [http://www.nystagmusblog.co.uk Nystagmus Blog] &mdash; A blog about Nystagmus, A parent’s perspective
*[http://www.ncbi.nlm.nih.gov/bookshelf/br.fcgi?book=gene&part=xl-nystag  GeneReview/NIH/UW entry on FRMD7-Related Infantile Nystagmus]

{{Eye pathology}}

[[Category:Medical signs]]
[[Category:Vision]]

[[Category:Diseases of the eye and adnexa]]

[[ar:رأرأة]]
[[az:Nistaqm]]
[[bs:Nistagmus]]
[[ca:Nistagme]]
[[cs:Nystagmus]]
[[de:Nystagmus]]
[[et:Silmatõmblus]]
[[es:Nistagmo]]
[[fr:Nystagmus]]
[[hr:Patološki nistagmus]]
[[it:Nistagmo]]
[[he:ניסטגמוס]]
[[nl:Nystagmus (aandoening)]]
[[ja:眼球振盪]]
[[no:Nystagmus]]
[[pl:Oczopląs]]
[[pt:Nistagmo]]
[[ru:Нистагм]]
[[simple:Nystagmus]]
[[sh:Nistagmus]]
[[fi:Nystagmus]]
[[sv:Nystagmus]]
[[Category:2Fix]]