Pathologic nystagmus

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Nystagmus
190px
Horizontal optokinetic nystagmus, a normal (physiological) form of nystagmus.
ICD-10 H55., H81.4.
ICD-9 379.50, 794.14
DiseasesDB 23470
MeSH D009759

Pathologic nystagmus is a form of involuntary 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 canals, otolith organs, and the vestibulocerebellum.

Pathological nystagmus generally causes a degree of vision impairment, although the severity of such impairment varies widely. Also, many blind people have nystagmus, which is one reason that some wear dark glasses.[1]

Prevalence

Nystagmus is a relatively common clinical condition, affecting one in every 5,000 to 10,000 individuals.[citation needed] One survey in Oxfordshire, England, reported that one in every 670 children has manifesting nystagmus by the age of two.[2] 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.[3]

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.[4] 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 drugs (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:

X-linked infantile nystagmus is associated with mutations of the gene FRMD7, which is located on the X chromosome.[5][6]

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).[7][8] CSNB-2 involves mutations of CACNA1F, a voltage-gated calcium channel that, when mutated, does not conduct ions.[9]

Acquired

Diseases

Some of the diseases that present nystagmus as a pathological sign:

Toxic/metabolic

Nystagmus from toxic or metabolic reasons could be the result of the following:

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.:

Other causes

Diagnosis

Nystagmus is very noticeable but little recognized. Nystagmus can be clinically investigated by using a number of non-invasive standard tests. The simplest one is Caloric reflex test, in which one 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),[13] or even less invasive devices called videonystagmograph (VNG),[14] 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.[15]

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[16], levetiracetam, 3,4-diaminopyridine, 4-aminopyridine, and acetazolamide.[17] Several therapeutic approaches, such as contact lenses,[18] drugs, surgery, and low vision 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.

Current UK Research Projects

See also

References

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External links

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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

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  1. ↑ "nystagmus". Retrieved 2007-06-07. 
  2. ↑ "American Nystagmus Network-About Nystagmus". Retrieved 2007-06-07. 
  3. ↑ Sarvananthan, N.; Surendran, M.; Roberts, E.; Jain, S.; Thomas, S.; Shah, N.; Proudlock, F.; Thompson, J.; McLean, R. (2009). "The prevalence of nystagmus: the Leicestershire nystagmus survey". Investigative ophthalmology & visual science. 50 (11): 5201–5206. doi:10.1167/iovs.09-3486. PMID 19458336.  edit
  4. ↑ Lua error in package.lua at line 80: module 'Module:Citation/CS1/Suggestions' not found.
  5. ↑ Self, J.; Lotery, A. (2007). "A review of the molecular genetics of congenital Idiopathic Nystagmus (CIN)". Ophthalmic genetics. 28 (4): 187–191. doi:10.1080/13816810701651233. PMID 18161616.  edit
  6. ↑ Li N, Wang L, Cui L; et al. (2008). "Five novel mutations of the FRMD7 gene in Chinese families with X-linked infantile nystagmus". Mol. Vis. 14: 733–8. PMC 2324116 Freely accessible. PMID 18431453. 
  7. ↑ Poopalasundaram, S.; Erskine, L.; Cheetham, M.; Hardcastle, A. (2005). "Focus on molecules: nyctalopin". Experimental eye research. 81 (6): 627–628. doi:10.1016/j.exer.2005.07.017. PMID 16157331.  edit
  8. ↑ Leroy, B.; Budde, B.; Wittmer, M.; De Baere, E.; Berger, W.; Zeitz, C. (2009). "A common NYX mutation in Flemish patients with X linked CSNB". The British journal of ophthalmology. 93 (5): 692–696. doi:10.1136/bjo.2008.143727. PMID 18617546.  edit
  9. ↑ Peloquin, J.; Rehak, R.; Doering, C.; McRory, J. (2007). "Functional analysis of congenital stationary night blindness type-2 CACNA1F mutations F742C, G1007R, and R1049W". Neuroscience. 150 (2): 335–345. doi:10.1016/j.neuroscience.2007.09.021. PMID 17949918.  edit
  10. ↑ Dorigueto RS, Ganança MM, Ganança FF (2005). "The number of procedures required to eliminate positioning nystagmus in benign paroxysmal positional vertigo". Rev Bras Otorrinolaringol (Engl Ed). 71 (6): 769–75. PMID 16878247. 
  11. ↑ Christmas, David M. B. "‘Brain shivers’: from chat room to clinic ". The Psychiatrist (2005) 29: 219-221. doi: 10.1192/pb.29.6.219
  12. ↑ Lua error in package.lua at line 80: module 'Module:Citation/CS1/Suggestions' not found.
  13. ↑ Markley, BA (2007). "Introduction to electronystagmography for END technologists". American journal of electroneurodiagnostic technology. 47 (3): 178–89. PMID 17982846.  edit
  14. ↑ Mosca, F; Sicignano, S; Leone, CA (2003). "Benign positional paroxysmal vertigo: videonystagmographic study using rotatory test". Acta otorhinolaryngologica Italica : organo ufficiale della Societa italiana di otorinolaringologia e chirurgia cervico-facciale. 23 (2): 67–72. PMID 14526552.  edit
  15. ↑ Eggert, T. (2007). "Eye movement recordings: methods". Developments in ophthalmology. 40: 15–34. doi:10.1159/0000100347. PMID 17314477.  edit
  16. ↑ Memantine/Gabapentin for the treatment of congenital nystagmus. PMID: 17764629
  17. ↑ Groves, Nancy. Many options to treat nystagmus, more in development. Ophthalmology Times, March 15, 2006. [1]
  18. ↑ Lua error in package.lua at line 80: module 'Module:Citation/CS1/Suggestions' not found.
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