Interernal ophthalmoplegia

Intraocular ophthalmoplegia is a kind of disorder of horizontal eye movements that develops when the medial (posterior) longitudinal fasciculus is damaged (it provides a "bundle" of eyeballs in gaze movements) in the middle part of the variolium bridge at the level of nuclei III and VI with cranial nerves. There is a violation of friendly eye movements when looking to the side and double vision, since the impulses to the lateral rectus muscle pass badly, and to the medial rectus muscle - normal.

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The main causes of internuclear ophthalmoplegia:

• multiple sclerosis,
• cerebral infarction,
• tumors of the brainstem and IV ventricle,
• trunk encephalitis,
• meningitis (especially tuberculosis)
• drug intoxication (tricyclic antidepressants, phenothiazines, barbiturates, diphenin),
• metabolic encephalopathies (hepatic encephalopathy, maple syrup disease)
• systemic lupus erythematosus,
• craniocerebral trauma,
• degenerative diseases (progressive supranuclear palsy, spin-cerebellar degeneration),
• syphilis,
• malformation of Arnold-Chiari,
• syringobulbia pseudo-nuclear ophthalmoplegia (myasthenia gravis, Wernicke's encephalopathy, Guillain-Barre syndrome, Miller Fisher syndrome, exotrophy).

There are two variants of internuclear ophthalmoplegia: anterior and posterior.

I. Front internuclear ophthalmoplegia

With high damage to the medial longitudinal bundle near the nucleus of the third nerve, bilateral involvement of the medial rectus muscles of the eye is observed and the mechanism of convergence is upset; the eyes are in a state of divergence. In fact, there is a paralysis of both medial rectus muscles of the eye.

This syndrome occurs in hemorrhages in the brain stem area against the background of hypertension and multiple sclerosis. The divergence of the eyes can be complicated by oblique deviation (skew deviation), in which one eye looks up and out, and the other - down and out. This picture is sometimes complicated by a kind of vertical nystagmus, which in one eyeball is directed upward, and in the other - downwards with a cyclic alternation of the direction of the nystagmus.

II. Rear internuclear ophthalmoplegia

If the medial longitudinal fasciculus is damaged below (in the region of the variolic bridge), then in the lateral gaze movements there is a deficiency of the medial rectus muscle of the eye: that is, when looking, for example, to the right, there is a deficiency of the involved medial rectus muscle on the left (insufficiency of reduction, adduction); at a sight left there is a failure of reduction of the right medial rectus muscle. With these vzor movements, the abduction (abduction) is performed normally in any direction (but on the abduction side in typical cases noticeable nystagmus is observed); reduction (adduction) always suffers, in whatever direction the gaze is directed; and on the side of casting nystagmus is expressed minimally. This bilateral phenomenon, pathognomonic for multiple sclerosis, is sometimes called "internuclear ophthalmoplegia with atactic nystagmus."

One-sided internuclear ophthalmoplegia

One-sided internuclear ophthalmoplegia is usually caused by an occlusive vascular process in the paramedian region of the brainstem, as the vessels here provide a strictly unilateral hematopoietic supply to the midline.

Asymmetric internuclear ophthalmoplegia

Asymmetric internuclear ophthalmoplegia can also be observed in multiple sclerosis.

Transient bilateral ambulatory ophthalmoplegia

An important, relatively benign, cause of transient bilateral interocular ophthalmoplegia is the toxic effect of anticonvulsants, especially diphenin and carbamazepine.

There is a syndrome of mixed disturbance of eye movements in lesions in the field of the variolium bridge, when a combination of internuclear ophthalmoplegia in one direction and paralysis of the horizontal gaze are observed in the other. In this case, one eye is fixed along the midline during all horizontal movements; the other eye can only perform abduction with a horizontal nystagmus in the direction of abduction ("one and a half syndrome"). Damage in such cases affects the bridge center of the eye plus the internuclear fibers of the ipsilateral medial longitudinal fascicle and is caused, as a rule, by a vascular (more often) or demyelinating disease.