What is Internuclear Ophthalmoplegia?
Internuclear ophthalmoplegia is a condition affecting eye movement that happens due to damage in a part of the brain called the medial longitudinal fasciculus. This issue is identified by the inability to move the eye on the same side as the damage towards the nose, combined with involuntary back-and-forth movement of the eye on the opposite side. The medial longitudinal fasciculus, which is integral to coordinating the movements of both eyes, was first discovered back in the 1870s. However, internuclear ophthalmoplegia as a condition was not defined until 1903.
What Causes Internuclear Ophthalmoplegia?
Internuclear ophthalmoplegia is a condition that happens when there’s damage to a part of the brain called the medial longitudinal fasciculus (MLF). The MLF is like a communication highway in the brain that sends important information needed for coordinating different types of eye movements.
This information highway runs close to the middle of the brain and passes through a region called the brainstem, which is located at the base of the brain. More specifically, the MLF runs in front of two important areas of the brain, the cerebral aqueduct in the midbrain and the fourth ventricle located in the pons and medulla.
The different types of eye movements that are coordinated by the MLF include saccades (quick voluntary shifts of attention from one object to another), smooth pursuit (keeping an eye on a moving object while the head remains still), and the vestibulocochlear reflex (stabilizing the eyes during head movements).
The MLF forms a network of communication between all the parts of the brain that control eye movements. If there’s any damage to the MLF, it can cause problems with side-to-side eye movements. This can make tasks like reading or tracking a moving object very challenging.
Risk Factors and Frequency for Internuclear Ophthalmoplegia
Internuclear ophthalmoplegia is a condition that can be caused by various factors and occurs in different age groups. Around one-third of these cases occur in older individuals due to infarctions, typically seen on one side. Another third is related to demyelinating disorders such as multiple sclerosis (MS), usually affecting both sides in young adults and adolescents. In fact, about 23% of people with MS experience this condition. Other causes range from trauma and infections, such as HIV and herpes zoster, to tumors and internal bleeding in the brainstem.
- About 1/3 of internuclear ophthalmoplegia cases are due to infarctions and often affect older individuals.
- A similar proportion is caused by demyelinating disorders like MS, typically in young adults and adolescents.
- Approximately 23% of those with MS experience internuclear ophthalmoplegia.
- Other reasons include trauma, certain infections (HIV, syphilis, herpes zoster), tumors (medulloblastoma, glioma), and brainstem bleeding.
- The condition affects males and females almost equally.
- About half of all cases are resolved within a year.
- It is rare in children, but important causes include tumors such as medulloblastoma and pontine gliomas, in addition to trauma, vasculitis, infarctions, and hemorrhage.
Signs and Symptoms of Internuclear Ophthalmoplegia
Internuclear ophthalmoplegia is a condition that affects the eye, causing varying severity of symptoms including blurry vision, double vision or dizziness when looking to the side. Some patients may also experience vertical double vision due to a misalignment of the eyes. This condition involves the disruption of the natural balance between the eyes and the inner ear, which results in skewed vision.
The key sign of internuclear ophthalmoplegia is difficulty moving the eye towards the nose, which can range from mild to severe. This is often accompanied by an involuntary movement of the eye when looking sideways. Some patients may be able to focus on a nearby target, which helps doctors confirm the diagnosis and determine the exact site of the damage. Doctors also look out for other signs related to the brain to help confirm diagnosis.
Lesions affecting both the part of the brain that controls horizontal gaze and the part that receives signals from the inner ear can cause “one and a half syndrome”. This condition results in losing all horizontal eye movements except for looking to the side. Unilateral internuclear ophthalmoplegia may also be associated with a condition causing misalignment of the eyes. A rare disorder called wall-eyed bilateral internuclear ophthalmoplegia (WEBINO), is when both eyes have difficulty moving towards the nose, causing the eyes to look slightly outward.
Testing for Internuclear Ophthalmoplegia
For many patients suffering from internuclear ophthalmoplegia (a condition that affects eye movement), the diagnosis can often be determined through a physical examination by a healthcare provider. However, additional tests, such as neuroimaging, which helps to visualize the brain and nervous system, can also be used to uncover the root cause of the condition.
An MRI (Magnetic Resonance Imaging) scan can be particularly useful in these cases – it can reveal a visible abnormal area in up to 75% of patients. Specifically, for lesions triggered by a process known as demyelination (where the protective coating of nerve cells is damaged), proton density imaging, a type of MRI technique, is often the best choice.
Other supplementary tests, including blood tests and studies of the cerebrospinal fluid (fluid present in your brain and spine), can also be carried out. These can help to identify less common causes of the condition.
Treatment Options for Internuclear Ophthalmoplegia
The treatment of certain conditions depends on their root cause. Conditions such as acute strokes need patients to be admitted to the hospital for a check-up by a neurologist. Other conditions such as multiple sclerosis, infections, and systemic lupus erythematosus demand personalized care from a doctor.
Most patients who suffer from demyelination (a disease that damages the protective covering of nerve fibers), infections, and traumatic injuries generally make a full recovery. However, patients with issues in their blood vessels in the brain don’t recover as well. If internuclear ophthalmoplegia (a condition causing eye movement limitation) happens alone, patients likely have a better chance at recovery than if it’s accompanied by other neurological symptoms. Some research also shows that when there’s a visible lesion causing internuclear ophthalmoplegia, recovery can be more challenging.
Most patients with long-term internuclear ophthalmoplegia only have minor symptoms. If someone has double vision, a symptom of this condition, treatments such as botulinum toxin injections or Fresnel prisms may help. For patients with wall-eyed bilateral internuclear ophthalmoplegia (affecting eye movement in both eyes), doctors may suggest surgery to correct the misalignment.
What else can Internuclear Ophthalmoplegia be?
When trying to determine a patient’s illness, doctors may have to rule out other conditions with similar symptoms. In this case, the primary possibilities include:
- VI nerve palsy
- Lateral gaze palsy
- One-and-half syndrome
What to expect with Internuclear Ophthalmoplegia
The outlook for recovery depends on what is causing the ophthalmoplegia, a condition where some or all the eye’s movement muscles are weak or paralyzed. Cases caused by damage to the protective covering of nerve fibers in the brain (a process known as brainstem demyelination) or physical injury don’t usually have a positive outlook.
Possible Complications When Diagnosed with Internuclear Ophthalmoplegia
The problems resulting from ophthalmoplegia, a condition affecting eye movement, are mainly related to vision loss. However, more serious issues that can emerge are associated with malfunction of the brainstem. These can include aspiration pneumonia (a lung infection from inhaling food or drink), deep vein thrombosis (a blood clot in a deep vein), respiratory arrest (sudden stopping of breathing), bedsores (skin and underlying tissue damage from prolonged pressure), and other infections.
Complications of Ophthalmoplegia:
- Vision related issues
- Aspiration pneumonia
- Deep vein thrombosis
- Respiratory arrest
- Bedsores
- Other infections
Preventing Internuclear Ophthalmoplegia
It’s important for patients to understand what is causing their ophthalmoplegia, a medical condition that affects the ability to control eye movements. The doctor should let the patient know about their situation and how it might progress over time. It’s also necessary for caregivers to learn the significance of gentle handling and providing proper nourishment. This can be instrumental in managing the condition and making the patient more comfortable.
