^

Health

Internuclear ophthalmoplegia.

, medical expert
Last reviewed: 04.07.2025
Fact-checked
х

All iLive content is medically reviewed or fact checked to ensure as much factual accuracy as possible.

We have strict sourcing guidelines and only link to reputable media sites, academic research institutions and, whenever possible, medically peer reviewed studies. Note that the numbers in parentheses ([1], [2], etc.) are clickable links to these studies.

If you feel that any of our content is inaccurate, out-of-date, or otherwise questionable, please select it and press Ctrl + Enter.

Internuclear ophthalmoplegia is a peculiar disorder of horizontal eye movements that develops when the medial (posterior) longitudinal fasciculus (it provides a "ligament" of the eyeballs during gaze movements) in the middle part of the pons at the level of the nuclei of the III and VI cranial nerves is damaged. There is a violation of the concomitant movements of the eyes when looking to the side and double vision, since impulses to the lateral rectus muscle of the eye pass poorly, and to the medial rectus muscle - normally.

trusted-source[ 1 ], [ 2 ], [ 3 ], [ 4 ], [ 5 ]

The main causes of internuclear ophthalmoplegia are:

  • multiple sclerosis,
  • brainstem infarction,
  • tumors of the brainstem and fourth ventricle,
  • brainstem encephalitis,
  • meningitis (especially tuberculosis)
  • drug intoxication (tricyclic antidepressants, phenothiazines, barbiturates, diphenin),
  • metabolic encephalopathies (hepatic encephalopathy, maple syrup urine disease)
  • systemic lupus erythematosus,
  • traumatic brain injury,
  • degenerative diseases (progressive supranuclear palsy, spinocerebellar degenerations),
  • syphilis,
  • Arnold-Chiari malformation,
  • syringobulbia pseudointernuclear ophthalmoplegia (myasthenia, Wernicke's encephalopathy, Guillain-Barré syndrome, Miller Fisher syndrome, exotropia).

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

I. Anterior internuclear ophthalmoplegia

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

This syndrome occurs with hemorrhages in the brainstem area against the background of arterial hypertension and multiple sclerosis. Divergence of the eyes can be complicated by skew deviation, in which one eye looks up and outward, and the other down and outward. This picture is sometimes complicated by a peculiar vertical nystagmus, which is directed up in one eyeball and down in the other, with cyclic alternation of the direction of nystagmus.

II. Posterior internuclear ophthalmoplegia

If the medial longitudinal fasciculus is damaged below (in the area of the pons), then with lateral gaze movements, a deficiency of the medial rectus muscle of the eye is observed: that is, when looking, for example, to the right, a deficiency of the involved medial rectus muscle on the left is detected (insufficiency of adduction, adduction); when looking to the left, a deficiency of adduction of the right medial rectus muscle is detected. With these gaze movements, abduction is performed normally in any direction (but on the side of abduction, noticeable nystagmus is typically observed); adduction always suffers, no matter which way the gaze is directed; moreover, on the side of adduction, nystagmus is expressed minimally. This bilateral phenomenon, pathognomonic for multiple sclerosis, is sometimes called "internuclear ophthalmoplegia with ataxic nystagmus."

Unilateral internuclear ophthalmoplegia

Unilateral internuclear ophthalmoplegia is usually caused by an occlusive vascular process in the paramedian region of the brainstem, since the vessels here provide a strictly unilateral blood supply to the midline.

Asymmetric internuclear ophthalmoplegia

Asymmetric internuclear ophthalmoplegia may also be seen in multiple sclerosis.

Transient bilateral internuclear ophthalmoplegia

An important, relatively benign, cause of transient bilateral internuclear ophthalmoplegia is the toxic effects of anticonvulsant drugs, especially phenytoin and carbamazepine.

A syndrome of mixed eye movement disorder is known with damage to the pons, when a combination of internuclear ophthalmoplegia in one direction and horizontal gaze paralysis in the other is observed. In this case, one eye is fixed along the midline during all horizontal movements; the other eye may be able to perform only abduction with horizontal nystagmus in the direction of abduction ("one-and-a-half syndrome"). The damage in such cases affects the pontine gaze center plus the internuclear fibers of the ipsilateral medial longitudinal fasciculus and is usually caused by a vascular (more often) or demyelinating disease.

You are reporting a typo in the following text:
Simply click the "Send typo report" button to complete the report. You can also include a comment.