Nystagmus or eye tremors: Optokinetic, Vestibular and Rotary

Nystagmus is a medical term used to describe oscillating, rhythmic and uncontrollable eye movements.

You can see the pupil, which jumps in one direction and then involuntarily and with the same frequency, the movement resembles that of a pendulum.

The movement can be of the following type:

• induced
• provokes
• spontaneous.

The possible direction of movement of the eyes is:

• lateral (horizontal nystagmus),
• up and down (vertical nystagmus),
• vortical.

Nystagmus often occurs when an object becomes peripherally visible or when objects are viewed moving at a very high speed.

In most cases, nystagmus occurs during childhood or adolescence, but can also develop in adulthood.
Experts say that about one child in a thousand has this nystagmus.

The rhythm of eye movements can still be divided into fast or slow.

1. The slow phase is physiologically or pathologically caused by a vestibular stimulus.
2. The fast phase is a rapid movement induced by the oculomotor system that controls eye movements.

Types of nystagmus

Pathological nystagmus
Pathological nystagmus occurs during the rotation of the trunk in relation to the head, which remains stationary in space. In this case, the disorder originates from the cervical spine.

This cervical nystagmus can be caused by:

• vascular compression of the vertebral arteries,
• proprioception (perception of the position of the body in space) through the cervical joints,
• Dysfunction of the upper cervical spine

Physiological nystagmus: Physiological nystagmus maintains a clear view during autorotation.
In many cases, for example during locomotion, the head movements are small and the vestibulo-ocular reflex is able to produce compensatory movements of the eyes

There are several types of physiological nystagmus:

• Optokinetic nystagmus is a physiological reaction of the eye muscles that occurs when moving objects are viewed (for example, looking out of a train window).
  The eye makes a slow movement to follow the object and then jumps back to capture another object.
  It is a physiological nystagmus that occurs in the first years of life, in some cases a few weeks after birth.
• Vestibular nystagmus (connected to the inner ear). The vestibular system works together with the eye movement system. If the ear receives special stimuli (such as the passive rotation of the head), the eyes move rhythmically and consequently the nystagmus occurs.
  If the communication between the two systems is not adequate, nystagmus can be observed.
  Vestibular nystagmus consists of involuntary eye movements caused by disorders of the inner ear (for example, tinnitus or deafness).
  This nystagmus is divided into:
  1. Central vestibular nystagmus, in this case, eye movement can occur in one or both directions.
  2. Peripheral-vestibular nystagmus, eye movement always occurs in the same direction.

Classification of nystagmus

Nystagmus can be congenital (congenital) or acquired due to an accident or disease.

Congenital nystagmus

Infantile nystagmus syndrome
Occurrence: 0-6 months
of life At this age, the following forms of nystagmus are possible:

1. Cogan congenital idiopathic or motor nystagmus (CIN)
   The newborn has nystagmus in all directions of vision, but the eyes and motor development are clinically normal.
   This diagnosis is made only if all neurological and ocular abnormalities have been excluded.
2. Sensory nystagmus according to Cogan
   Concomitant symptom of congenital bilateral visual impairment with reduced visual acuity.

A child with sensory or oculomotor deficits of the eyes does not necessarily have to suffer from nystagmus.

Acquired nystagmus

Acquired nystagmus can be caused by:

• disease (multiple sclerosis, brain tumor, diabetogenic neuropathy),
• accident (craniocerebral trauma),
• neurological problem (side effect on medication).

Hyperventilation, flickering light in front of the eyes, nicotine and vibrations can cause nystagmus in rare cases.
Some cases of acquired nystagmus may be treated by medication or surgery.

Spasm Nutans: This syndrome is characterized by the appearance of nystagmus, head swings and abnormal positions of the head (stiff neck).

Gaze-evoked nystagmus: This nystagmus occurs when the eyes are held away from the midline of the body.
This form arises from a disorder of the brainstem or from sedatives.
Nystagmus can get worse if the person is tired or stressed, or if he or she looks to the side (also called rebound nystagmus).

Convergence and retraction nystagmus: It is a provoked nystagmus that occurs with a violation of the midbrain (for example, in Parinaud’s syndrome or pinealom).

The eyeballs

• converge simultaneously to the center
• and then return to their starting position.

Convergence and retraction nystagmus occurs when the patient tries to perform an upward movement of the eyeballs that is obstructed or paralyzed.Opsoclonus: Opsoclonus is not a true nystagmus, but rather a high-frequency tremor with low amplitude and involuntary. It is often referred to as “dancing eyes and dancing feet” due to its connection to acute cerebellar ataxia of childhood.

Opsoclonus can be the sign of neuroblastoma.

Classification of nystagmus based on the situation

• Monocular (unilateral) or bilateral nystagmus. May affect one or both eyes.
• Willful nystagmus: Some people can trigger deliberate nystagmus. Fine, fast and horizontal movements can be generated and maintained for a short time.
• Miner’s nystagmus: This form of nystagmus occurs in people who work in the dark for long periods of time.
• Rocking nystagmus: in this case, the eyes perform opposite movements, while one goes up, the other goes down.
• Spontaneous or induced nystagmus: This form of nystagmus occurs randomly independently of the head posture.
• Manifest nystagmus: It is always present while latent nystagmus occurs when the eye is covered.
• Manifest latent nystagmus: Always present, but may intensify when the eye is covered.
• Fixation nystagmus: Occurs only when the eyes fix an object.
• Dissociated nystagmus: The manifestation in one eye is not synchronized with the other eye.

Classification of nystagmus based on movements

• Jerk or jerky nystagmus: The eyes move slowly in one direction and then quickly return to the starting position.
• Pendulum nystagmus: The speed of eye movements is the same in both directions.
• Sakkadic or biphasic nystagmus: Depending on the direction, the speed is different. The fast component (fast phase) defines the designation of the direction of the nystagmus (a saccadic nystagmus to the right has a slow phase to the left and the fast phase to the right).
• Lateral nystagmus: The eyes move in horizontal jerk motion (from side to side).
• Rotary or torsional Nystagmus: The eyes move around the visual axis.
• Postrotatory nystagmus: This is a form of vestibular nystagmus that occurs when the whole body is rotated and then stops.
  For example, you can observe it in a patient on a rotating swivel chair, which then suddenly stops.
• Geotropic nystagmus worsens when rotating to the sick side.
• Apogeotropic nystagmus worsens when the head is turned to the healthy side.

Symmetrical vertical nystagmus

• Vertically upward swinging nystagmus:
  Description – It is a nystagmus in saccades, in which the fast phase is directed upwards.
  It appears in the primary position of the eye and increases when looking downwards.
  Related disease – it is often seen as a side effect of anticonvulsant drugs, but it can also be seen in cerebellar disease and cerebellum-bridge angle abnormalities.
• Vertically Downward Swinging Nystagmus:
  Description – This saccadic-like nystagmus has a rapid downward phase that is present in the primary position and worsens when looking down.
  Related diseases – there are several causes, including:
• anomaly at the craniocervical junction (for example, Arnold-Chiari syndrome),
• Cerebellar degeneration
• drug intoxication (especially with lithium, phenytoin, carbamazepine and barbiturates),
• Wernicke’s encephalopathy,
• demyelination,
• Encephalitis of the brainstem and hydrocephalus.

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