- Pathologic nystagmus
MeshID = D009759
Pathologic nystagmus is a form of involuntary
eye movement. It is characterized by alternating smooth pursuitin one direction and saccadic movementin 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 canals, otolith organs, and the vestibulocerebellum.
Pathological nystagmus generally causes a degree of
vision impairment, although the severity of such impairment varies widely. Sometimes it is the other way around — many blind people have nystagmus, which is one reason that some wear dark glasses. [cite web |url=http://www.drhull.com/EncyMaster/N/nystagmus.html |title=nystagmus |accessdate = 2007-06-07 |format= |work=]
Nystagmus is a relatively common clinical condition, affecting one in every 5,000 to 10,000 individuals.Fact|date=February 2007 One survey in Oxfordshire, England identified one in every 670 children by the age of two as manifesting nystagmus. [cite web |url=http://www.nystagmus.org/aboutn.html |title=American Nystagmus Network-About Nystagmus |accessdate = 2007-06-07 |format= |work=]
*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 persons head is in a specific position.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] 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.
The cause for pathological nystagmus may be
congenital, idiopathic, secondary to a pre-existing neurological disorderor may be induced temporarily by disorientation (such as on roller coaster rides) or certain drugs ( alcoholand other central nervous systemdepressants and stimulants, such as lithium salts, phenytoinand ecstasy).
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). Congential 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.
Idiopathic:* Albinism:* Aniridia:* Leber's congenital amaurosis:*Bilateral optic nerve hypoplasia:*Bilateral congenital cataracts:* Rod monochromatism:* Optic nerveor macular disease:* Persistent tunica vasculosa lentis
*Nystagmus blockage syndrome
X-linked infantile nystagmus is associated with
FRMD7.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=]
Some of the diseases which present nystagmus as a pathological sign are:
Benign Paroxysmal Positional Vertigocite 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]
Stroke(the most common cause in older people)
Ménière's diseaseand other balance disorders
Lateral medullary syndrome
Optic nerve hypoplasia
Superior canal dehiscence syndrome
Nystagmus from toxic or metabolic reasons could be the result of e.g.:
*Alcohol intoxication (see above)
Lysergic acid diethylamide(LSD)
*Other anticonvulsants or sedatives
Central nervous system disorders
If the pathologic nystagmus is based in the
central nervous system(CNS), such as with a cerebellar problem, the nystagmus can be in any direction "including" horizontal. Purely vertical nystagmus is usually central in origin.
Causes include e.g.:
*Vestibular Pathology (
Ménière's disease, SCDS ( superior canal dehiscence syndrome), BPPV, Labyrinthitis)
Trochlear nervemalfunctioncite book
title=Kliniska färdigheter: Informationsutbytet mellan patient och läkare
Nystagmus is very noticeable, but little recognised. Nystagmus can be clinically investigated by using a number of non-invasive standard tests. The simplest one is
Caloric reflex test. In a caloric reflex test, one external auditory meatus is irrigated with warm or cold water. The temperature gradient provokes the stimulation of the vestibulocochlear nerveand the consequent nystagmus.
The resulting movement of the eyes may be recorded and quantified by special devices called
electronystagmograph(ENG), which is a form of electrooculography(an electrical method of measuring eye movements using external electrodes) or even less invasive devices called videoonystagmograph(VNG), which is a form of videooculography(VOG) (a video-based method of measuring eye movements using external small cameras built into head masks). Special swinging chairs with electrical controls are also used in this test to induce rotatory nystagmus.
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
baclofencould 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[ Memantine/Gabapentin for the treatment of congenital nystagmus. [http://www.ncbi.nlm.nih.gov/pubmed/17764629 PMID: 17764629] ] , levetiracetam, 3,4-diaminopyridine, 4-aminopyridine, and acetazolamide.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] ] Several therapeutic approaches, such as contact lenses,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= |url=http://jnnp.bmj.com/cgi/pmidlookup?view=long&pmid=14742616] drugs, surgery, and low visionrehabilitation 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.
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]
* [http://www.nystagmus.org American Nystagmus Network] — US-based support organisation
* [http://www.nystagmusnet.org Nystagmus Network UK] — UK-based support organisation
* [http://www.nystagmus.co.uk nystagmus.co.uk] — a teenager's experiences of nystagmus and a friendly forum
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