Obnuclear oculomotor disorders

Friendly eye movements

Friendly eye movements are binocular movements, in which the eyes move synchronously and symmetrically in the same direction. There are 3 main types of movements: saccadic, smooth search, non-optical reflex. The saccadic and search movements are controlled at the brain and stem levels. Supranuclear disorders cause a paresis of the eye, characterized by a lack of diplopia and normal vestibulo-ocular reflexes (for example, oculocephalic movements and thermal stimulation).

Saccadic movements

At the heart of saccadic (jerky, intermittent) movements is the rapid location of the object on the fovea or the movement of the eyes from one object to another. This can be done arbitrarily or reflexively, which is initiated by the appearance of an object on the periphery of the field of view. Arbitrary saccades speed of localization of the mobile object are similar to the artillery system.

The conductive path of horizontal saccades begins in the premotor cortex (frontal eye fields). Hence, the fibers pass and contralateral center of horizontal eye movements in the stem paramedian reticular formation, therefore each frontal lobe initiates contralateral saccades. Irritative lesions can cause a deviation of the eye in the opposite direction.

Smooth Search Traffic

During search movements, fixation is retained on the site localized by the saccadic system. The stimulus is the movement of the image near the fovea. The movements are slow and smooth.

Conductive path begins in the pericristal cortex of the occipital lobe. The fibers end in the ipsilateral center of horizontal eye movements in the SPRF. Accordingly, each occipital lobe controls the search on the ipsilateral side.

Non-optical reflexes

The function of the neoptic (vestibular) reflexes is the preservation of the position of the eye with changes in the position of the head and body.

The conducting path starts from the labyrinths and proprioreceivers of the cervical muscles that transmit information about the movements of the head and neck. Afferent fibers form synapses in the vestibular nuclei and pass to the center of horizontal eye movements in the SPRF.

Paresis of horizontal view

Clinical Anatomy

Horizontal eye movements are generated by the center of horizontal movements in the SPRF. Fibers connect it with the ipsilateral nucleus of the VI pair of cranial nerves, carrying out the removal of the ipsilateral eye. To bring the contralateral eye, fibers from SPRF cross the middle line at the level of the trunk and in the contralateral medial longitudinal bundle reach the medial straight nucleus in the contralateral complex of the third pair of cranial nerves (which also receives an independent descending entrance from the vertex control centers), so stimulation of SPRF to one side causes friendly eye movements in the same direction. It is important to remember that when leaving SPRF, MPP immediately crosses the middle line AND rises to the opposite side. Loss of normal horizontal eye movements occurs when these paths are destroyed.

Symptoms

• The defeat of SPRL causes an ipsilateral paresis of the horizontal gaze (inability to look in the direction of the lesion).
• The defeat of MPP is responsible for the clinical syndrome of internuclear ophthalmoplegia. Left-hand

Causes of internuclear ophthalmoplegia

• demyelination
• cardiovascular disorders
• tumors of the brainstem and fourth ventricle
• injury
• encephalitis
• hydrocephalus
• progressive supranuclear palsy
• medicines
• distant effects of carcinoma

The internuclear ophthalmoplegia is characterized by the following:

• When looking to the right - insufficient reduction of the left and ataxic nystagmus of the right eye.
• The view to the left is normal.
• Convergence is intact with isolated lesions.
• Vertical nystagmus when trying to look up.

Combined defeat of SPRF and MPP on one side causes "syndrome one and a half". Left-sided lesion is characterized by the following:

• Ipsilateral paresis of the eye.
• Ipsilateral internuclear ophthalmoplegia.
• The only remaining movement is the retraction of the contralateral eye, accompanied by an ataxic nystagmus.

Vertical View Parheses

Clinical Anatomy

Vertical eye movements are generated by the center of the vertical gaze, known as the rostral interstitial nucleus of the MOS, which lies in the middle of the brain dorsal to the red nucleus. From the center of the vertical gaze, pulses pass into the nuclei of the eye muscles, controlling the vertical movements of both eyes. Cells that mediate the movements of the eyes up and down are mixed at the center of the vertical gaze, but when it is irritated, selective paralysis of the glance up and down is possible.

Dorsal midbrain Syndrome Parinaud

Symptoms

• The supernumerary paresis looks up.
• Correct position of the eyes in the primary position.
• Normal look down.
• Wide pupils with dissociation of reactions to light and approximation.
• Retraction of the eyelid (Collier symptom).
• Paralysis of convergence.
• Convergence-retraction nystagmus.

Causes

• children - stenosis of the Sylvian aqueduct, meningitis;
• in young people - demyelination, trauma and arteriovenous malformations;
• in the elderly - vascular lesions of the midbrain, volumetric formations of near-conductor gray matter and aneurysms of the posterior cranial fossa.

[1], [2], [3], [4], [5], [6]

Progressing supranuclear palsy

Progressing supranuclear palsy (Sleele-Kiciiardson-Olszewski syndrome) is a severe degenerative disease that develops in old age and is characterized by:

• A supranuclear paralysis of the eye, in which the movements downward are first violated.
• Later, with progression of the disease, movements upward are disturbed.
• Later, horizontal movements are violated, and in the end a full paresis of the eye develops.
• Pseudobulbar paresis.
• Extrapyramidal rigidity, ataxic gait and dementia.