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Nystagmus and similar-appearing disorders

 

Nystagmus

Nystagmus - a repeated movement of the eyeballs, following one after another. There are two types of nystagmus:

  • pendular oscillations (smooth sinusoidal oscillations);
  • saccadic oscillations (alternating slow phase and a corrective fast phase).

In healthy individuals nystagmus occurs in response to vestibular and optokinetic stimulation. To investigate the cause of nystagmus data is collected the patient's history (information about the reception of drugs, alcohol, etc.) and conducted a full examination of the movements of his eyeballs.

Pathological nystagmus occurs during damage mechanisms of gaze fixation. Vestibular, optokinetic and targeted tracking eye movements system interact in such way as to maintain a stable image on the retina. Neuronal integrator allows keep the visible object in sight. Damage to these systems cause nystagmus.

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Identification of nystagmus is done by tracking the object from the center to the periphery of the with a patient's stationary head.

 

Types of nystagmus

There are four types of nystagmus in neurological patients:

 

Congenital nystagmus

For congenital nystagmus are characteristic long-existing horizontal pendular or saccadic movements of the eyeballs. In some cases, congenital nystagmus accompanied by lesions of the visual pathway and the deterioration of patient's gaze. Mechanism and localization of lesions in congenital nystagmus not known.

 

Labyrinthine-vestibular nystagmus

Damage of the vestibular system causes a slow smooth phase and a corrective fast phase, which together form saccadic nystagmus ("saw tooth" type). This one-way movement of nystagmus slow phase reflects of the vestibular nuclei's tonic neuronal activity instability. Damage to the inner ear's semicircular canals causes a slow deviation of the eyeball toward the damaged semicircular canal, followed by rapid compensatory movement directed in the opposite direction from those of the semicircular canals.

Abnormal are also slow deviation of the eyeballs in the same direction, but according to the rules determined by the direction of nystagmus side quick corrective impulse (fast phase of nystagmus). This imbalance of vestibular tone usually leads to vertigo and oscillopsia (illusory movement of the surrounding objects) in the patient.

Damage of the peripheral regions of the vestibular system usually accompanied by damage to multiple semicircular canals. This causes an imbalance between the signals from the individual semicircular canals of the inner ear. In this case, nystagmus have more often mixed character:

  • in benign positional nystagmus in a patient usually develops vertically mixed-rotational nystagmus;
  • one sided destruction of the labyrinth in the patient appears a mixed horizontal-rotational nystagmus.

Peripheral vestibular nystagmus reduced by fixing the head and enhanced when changes in its position (pan, tilt, rotation).

In cases of the central vestibular relationship's lesions observed central balance disorder between the signals, coming from the different semicircular canals, as well as interrupted ascending vestibular or cerebellar-vestibular connection. Central vestibular nystagmus can visually resemble nystagmus, developing during semicircular canal's lesion, but the more common two-sided vertical (up and down), the rotational or horizontal nystagmus. Central vestibular nystagmus decreases slightly when fixing the patient's head and getting worse by its position change in space (pan, tilt and rotation).

Three types of labyrinthine-vestibular nystagmus are important to establish the location of the lesion - up, down, and horizontal (left, right) nystagmus:

  • Downward nystagmus when patient viewed straight usually observed when looking straight and amplified when looking to the side. Downward nystagmus caused by abnormalities of the posterior fossa, such as Arnold-Chiari malformation and platybasia, as well as multiple sclerosis, atrophy of the cerebellum, hydrocephalus, metabolic disorders, familial periodic ataxia;
  • Upward nystagmus when patient viewed straight is a consequence of the cerebellar vermis anterior division's lesions, as well as a diffuse lesion of the brain stem with Wernicke's encephalopathy, meningitis, or because of the side effects of drugs.
  • Horizontal (left, right) nystagmus in the initial position (when patient viewed straight), observed in case of the peripheral part of the vestibular apparatus lesions, and only occasionally in tumors of the posterior fossa malformation or Arnold-Chiari malformation.

Nystagmus, which occurs during focused eye movements, will detected when the eyeballs deviated from the center. The ability to hold the eyeballs in desired position will attenuated by the neuronal integrator's lesions in the brain stem. Asymmetric, but collaborative horizontal nystagmus with focused eyeballs movement appears in the case of a unilateral lesion of the cerebellum and in tumors of the cerebellopontine angle (acoustic neuroma). Common cause of horizontal nystagmus will also cause by receiving of sedatives and anticonvulsants. Horizontal nystagmus in which the fast phase upon actuation of the eyeball medially is slower than in abduction of the eyeball outwards (dissociated nystagmus), is a hallmark of internuclear ophthalmoplegia.

Converging pulsating nystagmus, that worse when attempting to lift up eyes, characterized by pulsating saccadic movements of the eyeballs toward each other. Usually convergent pulsating nystagmus accompanied by other symptoms of the posterior regions of the midbrain (Parinaud syndrome).

 

Periodic alternating nystagmus

In the case of periodic alternating nystagmus in a patient observed horizontal nystagmus when looking straight, periodically (every 1-2 minutes) changes its direction in the right and left. Can be marked as nystagmus that occurs when focused eye movements and nystagmus downward. This form of the disease (periodic alternating nystagmus) may be a hereditary and occurs in conjunction with craniovertebral anomalies, as well as in multiple sclerosis and poisoning of anticonvulsant. When non-hereditary nature of periodic of alternating nystagmus positive effect gives baclofen prescription to the patient.

 

Dissociated vertical nystagmus

In the case of dissociated vertical nystagmus will observed alternating movement of the eyeballs: while one eyeball moves upwards and inwards, and the other - downwards and outwards. Dissociated vertical nystagmus is indicative lesions of nuclei of the reticular formation of the midbrain, including the interstitial nucleus of Cajal. Dissociated vertical nystagmus occurs in tumors, which are located above the area of the sella turcica (craniopharyngioma), head injury, rarely with cerebral infarction. Dissociated vertical nystagmus is often associated with bitemporal hemianopsia.

 

Disease that resemble nystagmus

Nystagmus may resemble such eye movement disorders, such as:

  • convulsive twitching of the eyeballs with a distinctive square wave (small saccadic movements aside from the fixation point and back);
  • tremor of the eyeballs (horizontal pulsating waves);
  • opsoclonus (frequent saccadic oscillations);
  • myokymia of the superior oblique muscle (monocular rotator-vertical movements);
  • ocular bobbing (rapid deviation of the eyeballs downward with a slow return to top);
  • periodic eye movement in the horizontal direction with a change in the direction of deviation every few seconds.

Blurred vision and eye movement are a danger signal, the recognition of which greatly increases the knowledge of the doctor (neurologist and neurosurgeon) about the state of the patient. A neurologist or neurosurgeon, watchful referring to such visible signals, which can send the eye, not only detects and differentiates them from each other, but also understand their clinical significance.

 

 

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