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Nystagmus (ReelDx)

VIDEO-CASE-PRESENTATION-REEL-DX

Nystagmus Patient will present with →  rapid and repetitive movement of both eyes side to side

Nystagmus is an involuntary, rapid and repetitive movement of the eyes. Usually, the movement is side-to-side (horizontal nystagmus), but it can also be up and down (vertical nystagmus) or circular (rotary nystagmus). The movement can vary between slow and fast, and it usually involves both eyes.

  • Down/upbeat: CNS dysfunction
  • Vestibular (horizontal): labyrinth or vestibular nerve dysfunction
  • Gaze-evoked: most common and often benign

There are two types of nystagmus: congenital and acquired:

  1. Congenital nystagmus develops in infancy, usually between six weeks and three months of age. Sensory nystagmus also occurs early in life and is related to poor vision caused by a variety of eye conditions, including cataract (cloudiness of the eye's lens), strabismus (eye misalignment) and optic nerve hypoplasia. As they get older, children with nystagmus don't see the world as shaky, but they will probably develop less clear vision.
  2. Acquired nystagmus occurs later in life and has a variety of causes, including an association with serious medical conditions. Unlike children with nystagmus, adults who acquire nystagmus may see images as shaky.

Nystagmus is very noticeable but rarely recognized.

Nystagmus can be clinically investigated by using a number of 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 special devices called electronystagmograph (ENG), a form of electrooculography (an electrical method of measuring eye movements using external electrodes), or even less invasive devices called videonystagmograph (VNG), 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 can be used to induce rotatory nystagmus.

Orthoptists may also use an optokinetic drum, or electrooculography to assess a patient's eye movements.

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, levetiracetam, 3,4-diaminopyridine, 4-aminopyridine, and acetazolamide.

Several therapeutic approaches, such as contact lenses, drugs, surgery, and low vision rehabilitation have also been proposed. For example it has been proposed that mini-telescopic eyeglasses suppress nystagmus.

Surgical treatment of Congenital Nystagmus is aimed at improving the abnormal head posture, simulating artificial divergence or weakening the horizontal recti muscles. Clinical trials of a surgery to treat nystagmus (known as tenotomy) concluded in 2001. Tenotomy is now being performed regularly at numerous centres 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.

Acupuncture has conflicting evidence as to having beneficial effects on the symptoms of nystagmus. Benefits have been seen in treatments where acupuncture points of the neck were used, specifically points on the sternocleidomastoid muscle.

Benefits of acupuncture for treatment of nystagmus include a reduction in frequency and decreased slow phase velocities which led to an increase in foveation duration periods both during and after treatment. By the standards of Evidence-based medicine, the quality of these studies can be considered poor.

Physical therapy or Occupational therapy is also used to treat nystagmus. Treatment consist of learning compensatory strategies to take over for the impaired system.

Question 1
A patient presents with a 3-day history of vertigo associated with turning over in bed, which lasts for several minutes. There are no other symptoms of the ear. Dix–Hallpike testing shows rotary nystagmus, which diminishes with repeated testing. Which of the following is the most likely diagnosis?
A
central nervous system (CNS) lesion
Hint:
Central lesions often have dissociation of the vertigo and nystagmus. The nystagmus in this condition is often vertical and without fatigability with repeated testing.
B
positional vertigo
C
Labyrinthitis
D
Meniere disease
E
vestibular neuronitis
Question 1 Explanation: 
This patient has positional vertigo, which is assumed to be caused by movement of a small canalith within the inner ear. This is a benign process that is often self-limited. The Dix–Hallpike is positional testing that confirms this type of vertigo. Central lesions often have dissociation of the vertigo and nystagmus. The nystagmus in this condition is often vertical and without fatigability with repeated testing. The other three options will all have vertigo that is not altered by position and have additional ear symptoms such as tinnitus or hearing loss. In benign paroxysmal positional vertigo, positional exercises are helpful in quickening its resolution. Canalith repositioning procedures are effective at resolving the vertigo in about 80% of cases with just one outpatient treatment.
Question 2
A 39-year-old woman presents to the ED with agitation, tremors, visual hallucinations, fever, and tachycardia. The eye examination reveals nystagmus and a sixth cranial nerve palsy. Which of the following conditions best describes this clinical scenario?  
A
Korsakoff psychosis
B
Wernicke encephalopathy
C
acute dystonia
D
acute cocaine toxicity
E
trigeminal neuralgia
Question 2 Explanation: 
Wernicke encephalopathy is a potentially fatal neurologic disorder found in alcoholics with poor nutritional status that is caused by chronic vitamin B6 deficiency. Alcoholism interferes with gastrointestinal absorption of vitamin B6 and impairs conversion of vitamin B6 to its active metabolite. In many patients, concomitant liver disease impairs storage of vitamin B6. The administration of glucose to an alcoholic patient with an inadequate supply of thiamine may precipitate this disorder. Clinical features include the triad of abnormal mental status, ophthalmoplegia, and gait ataxia. Patients are often disoriented, forgetful, and unable to recognize familiar objects. With prompt therapy, the ophthalmoplegia usually resolves within hours and the coma resolves in hours to days, but the memory deficit may never resolve. Thiamine 100 mg administered intravenously is the treatment of choice. Thiamine 100 mg intravenous administration is continued daily until the patient has achieved proper oral nutritional status. It is essential that thiamine be given prior to the administration of glucose.
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