Pathologic nystagmus

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Symptom/Sign: Nystagmus
Classifications and external resources
ICD-10 H55.
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. Sometimes it is the other way around — many blind people have nystagmus, which is one reason that some wear dark glasses.[1]

Contents

[edit] 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 identified one in every 670 children by the age of two as manifesting nystagmus. [2]

[edit] 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 persons head is in a specific position.[3] 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 Head Shake nystagmus occurs after an imbalance is created between a normal side and a diseased side by stimulation of the vestibular system by rapid shaking 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 results in up and down-beat nystagmus.

[edit] Causes

The cause for pathological nystagmus may be congenital, idiopathic, secondary to a pre-existing neurological disorder or may be induced temporarily by disorientation (such as on roller coaster rides) or certain drugs (alcohol and other central nervous system depressants and stimulants, such as lithium salts, phenytoin and ecstasy).

[edit] 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). 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.

  • Infantile:
  • Latent nystagmus
  • Nystagmus blockage syndrome

X-linked infantile nystagmus is associated with FRMD7.[4]

[edit] Acquired

[edit] Diseases

Some of the diseases which present nystagmus as a pathological sign are:

[edit] Toxic/metabolic

Nystagmus from toxic or metabolic reasons could be the result of e.g.:

[edit] 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.:

Cerebella Ataxia

[edit] Other causes

[edit] Diagnosis

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 nerve and 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.

[edit] 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[7], levetiracetam, 3,4-diaminopyridine, 4-aminopyridine, and acetazolamide.[8] Several therapeutic approaches, such as contact lenses,[9] 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.

[edit] Research

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

Current UK Research Projects

[edit] See also

[edit] References

  1. ^ nystagmus. Retrieved on 2007-06-07.
  2. ^ American Nystagmus Network-About Nystagmus. Retrieved on 2007-06-07.
  3. ^ Anagnostou E, Mandellos D, Limbitaki G, Papadimitriou A, Anastasopoulos D (June 2006). "Positional nystagmus and vertigo due to a solitary brachium conjunctivum plaque". J. Neurol. Neurosurg. Psychiatr. 77 (6): 790–2. doi:10.1136/jnnp.2005.084624. PMID 16705203. 
  4. ^ 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. PMID 18431453. 
  5. ^ 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. 
  6. ^ Lindgren, Stefan (1993). Kliniska färdigheter: Informationsutbytet mellan patient och läkare (in Swedish). Lund: Studentlitteratur. ISBN 91-44-37271-X. 
  7. ^ Memantine/Gabapentin for the treatment of congenital nystagmus. PMID: 17764629
  8. ^ Groves, Nancy. Many options to treat nystagmus, more in development. Ophthalmology Times, March 15, 2006. [1]
  9. ^ Biousse V, Tusa RJ, Russell B, et al (February 2004). "The use of contact lenses to treat visually symptomatic congenital nystagmus". J. Neurol. Neurosurg. Psychiatr. 75 (2): 314–6. PMID 14742616. 

[edit] External Links

Look up Nystagmus in Wiktionary, the free dictionary.

[edit] See also

v • d • e
Eye disease - pathology of the eye (primarily H00-H59, 360-379)
Eyelid, lacrimal system and orbit
Conjunctiva
Sclera and cornea
Iris and ciliary body
Lens
Choroid and retina
Optic nerve and visual pathways
Ocular muscles,
binocular movement,
accommodation and refraction
Visual disturbances and blindness
Pupil
Infectious diseases
Other
See also congenital