What Is Internuclear Ophthalmoplegia?

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With internuclear ophthalmoplegia (INO), proper side-to-side eye movement can become impaired. This is an eye movement disorder that affects the cranial nerve fibers that usually work together to allow the eyes to gaze in the same direction.

In cases of internuclear ophthalmoplegia, while it's still possible to move the eyes up and down, one or both eyes become unable to turn inward. When just one eye is affected, it can shake and appear to gaze straight ahead while the other turns sideways as it normally would.

Practitioner guides young woman's gaze

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Types of Internuclear Ophthalmoplegia

There are a few types of internuclear ophthalmoplegia. These include:

  • Unilateral cases in which only one eye is involved
  • Bilateral cases in which both eyes are impacted
  • Bilateral wall-eyed cases in which both eyes turn out

Internuclear Ophthalmoplegia Symptoms

Those with internuclear ophthalmoplegia typically have a variety of eye-related symptoms, including:

  • The person can be unable to turn the affected eye toward the nose when looking side to side (although the eye can sometimes turn inward when focusing on something up close).
  • Double vision can occur when looking to the side but may not be an issue when gazing straight ahead.
  • Involuntary eye shaking, known as nystagmus, may occur.
  • Vision may be blurry.
  • Eye movement may misalign vertically.
  • Dizziness may occur when looking to the side.

Causes

In cases of internuclear ophthalmoplegia, there is damage to the nerve fibers that control the side-to-side movements of the eyes. The nerves involved here include:

  • The third cranial nerve (oculomotor nerve): Controls many of your eye movements and movement of the eyelids
  • The fourth cranial nerve (trochlear nerve): Controls eye movement down and away from the nose
  • The sixth cranial nerve (abducens nerve): Controls the movement of the eye outward

While there can be a variety of factors that could potentially lead to internuclear ophthalmoplegia, there are two conditions that most commonly are the source. These include:

  • Having had a stroke: A stroke (blockage of a blood vessel or bleeding in the brain) tends to affect one eye. An infarction (death of tissue from lack of blood supply) accounts for about 38% of internuclear ophthalmoplegia cases.
  • Having multiple sclerosis: This disease attacks the myelin sheath, which protects nerve cells. It tends to affect both eyes in younger people. INO is seen in about 34% of cases of multiple sclerosis.

Other causes that can also bring on internuclear ophthalmoplegia include the following:

  • Lyme disease (an infection spread by tick bite)
  • Tumor
  • Head injury
  • Certain medications such as opioids (strong pain relievers), phenothiazines (antipsychotic agents), and tricyclic medication (antidepressants).
  • Nutritional deficiency such as lack of enough thiamine (B1), producing neurological symptoms (Wernicke encephalopathy)
  • Other infection

Diagnosis

To diagnose internuclear ophthalmoplegia, the doctor will examine your ability to move your eyes in concert.

They will also perform imaging exams such as a computed tomography (CT) scan and MRI magnetic resonance imaging (MRI) of the brain to determine where any damage may be found. In cases of multiple sclerosis, the MRI will be done with contrast to look for demyelination.

In most cases, in determining if this is indeed a case of internuclear ophthalmoplegia, an MRI is considered preferable to a CT scan.

Treatment

Determining how to best handle internuclear ophthalmoplegia depends on what the cause is. For example, internuclear ophthalmoplegia due to infection or inflammation may not be treated the same way as if it arose from multiple sclerosis or a stroke.

For cases arising from infection or inflammation, high doses of corticosteroids are often given. For patients with multiple sclerosis, improvement may be seen by treatment with a potassium channel blocker known as Ampyra (dalfampridine), often prescribed to improve a disturbance in gait.

Prognosis

In most cases, those with internuclear ophthalmoplegia can expect a good prognosis. This depends on the cause of the internuclear ophthalmoplegia and what treatment you receive.

In particular, those with internuclear ophthalmoplegia caused by lack of blood supply to the area or damage to the protective covering of the nerve usually recover. Your practitioner should give you an idea of what to expect from your treatment and the timeline to recovery.

Summary

Those with internuclear ophthalmoplegia have trouble with one or both of their eyes when trying to move them from side to side, although up and down movement may be no problem. This may affect just one or both eyes.

This is most commonly caused by a stroke or by multiple sclerosis, although other conditions such as infection, injury, or tumors can also be factors. Treatment for internuclear ophthalmoplegia depends on the source of the problem.

A Word From Verywell

If you have internuclear ophthalmoplegia, it can be troubling to suddenly not be able to move one or perhaps both of your eyes horizontally. The good news is that treatment can ultimately help resolve this in many cases. Talk with your doctor to find the right approach in your particular case and what you can do to help speed recovery.

4 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. University of Kentucky Healthcare. Internuclear ophthalmoplegia.

  2. Lee HN, Subrayan V. I think I have double vision? Or not? Internuclear ophthalmoplegia following right lacunar infarct. Med J Malaysia. 2021;76(6):950-952. PMID: 34806694.

  3. Nij Bijvank JA, van Rijn LJ, Balk LJ, Tan HS, Uitdehaag BMJ, Petzold A. Diagnosing and quantifying a common deficit in multiple sclerosis: internuclear ophthalmoplegiaNeurology. 2019;92(20):e2299-e2308. doi:10.1212/WNL.0000000000007499

  4. American Academy of Ophthalmology. Internuclear ophthalmoplegia.