Sixth Nerve Palsy

What is sixth nerve palsy?

Sixth nerve palsy is a condition where damage to a specific nerve disrupts eye movement and alignment. It’s usually one-sided (unilateral) and affects one eye only, but it can sometimes affect both eyes (bilateral). It’s also known as abducens (pronounced “ab-DEW-sens”) nerve palsy.

Your 12 cranial nerves connect to your brain directly and come in pairs, each having a left and right side. Your sixth cranial nerve pair, also known as the abducens nerve, connects to the lateral rectus muscle on each of your eyes.

Your lateral rectus muscles pull outward. They help your left eye look left and your right eye look right. Sixth nerve palsy disrupts signals traveling through the nerve, causing weakness or paralysis in the lateral rectus muscle.

How common is sixth nerve palsy?

Sixth nerve palsy is rare. Worldwide, there are between 370,000 and 900,000 new cases annually. In the U.S., there are between 15,000 and 37,000 new cases annually.

Anyone can develop sixth nerve palsy, but the odds increase significantly at age 50 and keep rising as you age. Available research indicates the risk of developing it is highest between ages 60 and 75.

What are the symptoms of sixth nerve palsy?

The symptoms of sixth nerve palsy happen because you can’t move or align your eyes properly. Some symptoms are possible with just sixth nerve palsy, while others may occur with conditions that can cause or contribute to sixth nerve palsy.

The main symptoms of sixth nerve palsy include:

• Eye misalignment (strabismus). If an affected eye can’t turn outward properly, it may cause a misalignment that’s visible to others. The misalignment may make an affected eye point inward (esotropia).
• Double vision (diplopia). This will get worse when you look at objects farther away or try to look to the affected side. It’ll improve when you look to the unaffected side (if you only have it in one eye).
• Changing position to see better. People with sixth nerve palsy may move their head or body when they can’t turn one or both eyes a certain way. Doing that may help them avoid double vision from eye misalignment.
• Nausea and vomiting. These can happen because of double vision and vision distortions. They can also happen because of conditions that can contribute to or cause sixth nerve palsy.
• Pain. Straining your eyes for extended times or having long-term vision disruptions can cause eye pain and headaches.

What causes sixth nerve palsy?

Sixth nerve palsy can happen with any condition or event that can damage your abducens nerve. And sections of it travel through your brain, so conditions that affect the brain itself can also affect the abducens nerve.

Many cases of sixth nerve palsy are idiopathic, meaning they happen for unknown reasons. But the majority of cases do have causes experts can find and diagnose. Those causes include:

• Injury.
• Infections.
• Circulatory problems.
• Systemic, inflammatory and metabolic conditions.
• Blood disorders, cancers and tumors.
• Other neurological conditions.
• Medical procedures.

Injury

Like the brain tissue surrounding it, the abducens nerve is vulnerable to damage from a head injury. Examples include:

• Concussions and traumatic brain injuries (TBIs).
• Skull fractures.
• Penetrating head injuries (like from sharp objects or projectiles).

Infections

Viruses, bacteria and other microbial invaders can attack your nervous system, including the abducens nerve. Examples include:

• Herpes zoster virus (the virus that causes shingles).
• Epstein-Barr virus (the virus that causes mononucleosis, or “mono”).
• Meningitis.
• Cytomegalovirus (CMV).
• Lyme disease.
• Syphilis.
• Fungal or parasitic infections.
• Ear infections (otitis media) when they spread or are severe.
• Orbital cellulitis (infection and inflammation of tissue around your eye).

Circulatory problems

Disruptions in blood flow and circulation inside your brain can affect the abducens nerve. Without blood flow, a problem called ischemia (pronounced “iss-KEY-me-uh”) develops. That’s when cells malfunction when they aren’t getting enough blood flow. The affected cells die if ischemia is severe and/or lasts too long.

Circulatory conditions and events that can cause sixth nerve palsy include:

• Lack of blood flow through the small blood vessels that supply the abducens nerve (microvascular ischemia).
• Strokes and transient ischemia attacks (TIAs).
• Brain aneurysms.
• Brain bleeds (intracranial hemorrhages).

Systemic, inflammatory and metabolic conditions

Conditions that affect multiple body systems can also cause or contribute to sixth nerve palsy. Examples include:

• Type 2 diabetes.
• Cardiovascular disease.
• High blood pressure (hypertension).
• Wernicke-Korsakoff syndrome.
• Multiple sclerosis (MS).
• Lupus (systemic lupus erythematosus).
• Amyloidosis.
• Sarcoidosis.
• Thyroid diseases.

Blood disorders, cancers and tumors

Conditions that affect your blood can cause increased pressure inside your skull, which can cause surrounding brain tissue to press on and damage the abducens nerve. And other growths inside your brain can press on the abducens nerve. Examples include:

• Leukemia.
• Lymphoma.
• Brain tumors (including cancerous and benign tumors).
• Cancers that metastasize to the brain.

Other neurological conditions

Many other neurological (nervous system-related) conditions can cause or contribute to sixth nerve palsy. Examples include:

• Migraines and cluster headaches.
• Idiopathic intracranial hypertension (high pressure inside your skull with an unknown cause).
• Hydrocephalus.
• Chiari malformation.
• Arteriovenous malformation (AVM).
• Cerebrospinal fluid (CSF) leak.

Medical procedures

Certain medical procedures or treatments can affect or damage the abducens nerve. Some examples include:

• Spinal tap (lumbar puncture). This can sometimes cause sixth nerve palsy if it leads to a drop in pressure inside your skull. Ordinarily, your brain “floats” in the surrounding cerebrospinal fluid (CSF). When CSF levels drop, your brain may sag downward, putting pressure on tissue at the bottom of your brain, including the abducens nerve.
• Epidural anesthesia. This can cause sixth nerve palsy for similar reasons to a spinal tap.
• Vaccines. In rare cases, certain vaccines can give you milder symptoms of the conditions they prevent. Fortunately, sixth nerve palsy is temporary and mild when this is the cause.
• Brain surgery or procedures like radiation therapy. These may damage the nerve when they affect nearby areas of brain tissue.

What are the risk factors for sixth nerve palsy?

Some people may have a higher risk of developing sixth nerve palsy. In many cases, a cause like those listed above may not be the main cause, but it might make it easier for something else to cause sixth nerve palsy. Examples include:

• Metabolic conditions like Type 2 diabetes.
• Circulatory conditions like high blood pressure (hypertension).
• Inflammatory or autoimmune conditions like multiple sclerosis.

What are the complications of sixth nerve palsy?

The complications of sixth nerve palsy depend strongly on the underlying cause and treatments used for this condition. Because these can vary widely, your healthcare provider is the best source of information about the possible or likely complications in your case and what you can do to avoid or minimize them.

One key complication providers will try to avoid in children is amblyopia (lazy eye). It happens when a child’s brain starts relying more and more on one eye and ignoring input from the other. The unused eye’s alignment will “drift” out of position and worsen.

How is sixth nerve palsy diagnosed?

A health care provider, such as an ophthalmologist, neurologist or neuro-ophthalmologist, can diagnose sixth nerve palsy using a combination of methods. Those include:

• Visual testing. A healthcare provider or eye care specialist will test your ability to move your eyes in certain ways to make sure the sixth nerve is the only one affected. That’s because sixth nerve palsy can happen in combination with palsy of other nearby nerves, especially ones that also control eye movement.
• Lab tests. These are a key way to determine if you have a metabolic condition, blood disorder, infection or other condition that lab tests can detect. Testing of your blood glucose or A1C levels is extremely likely. Tests may also examine other blood components like platelets, immune cells or antibody levels that might indicate an autoimmune disease.
• Magnetic resonance imaging (MRI). An MRI scan is essential to diagnosing sixth nerve palsy, especially in people under age 50. This test provides highly detailed images of the tissues inside your head, including the abducens nerve and surrounding brain tissue. It can help find or rule out very serious or dangerous conditions like strokes, cancer or tumors, etc.

How is sixth nerve palsy treated?

The treatments for sixth nerve palsy vary widely, and they usually fall into one of two categories:

• Stop whatever is causing the palsy.
• Treat the effects of the palsy and try to reverse them when possible and necessary.

The main factor is what’s causing it, but other factors play a role, too. Treating the underlying condition is usually enough for sixth nerve palsy to go away on its own. Because so many factors can determine the best treatment for sixth nerve palsy, your healthcare provider is the best source of information about the best treatment options. They can tailor the information to fit your specific situation and needs.

For many people, little or no treatment is necessary. If your case doesn’t appear to need treatment early on, your healthcare provider or eye specialist will schedule follow-up visits to monitor your condition. Treating the palsy will only happen if it becomes necessary. However, treating the effects of the palsy is still likely to happen.

Treating the palsy’s effects is a little more straightforward and usually involves minimizing or stopping the symptoms. Some of the treatments that help the effects of sixth nerve palsy include:

• Wearing an eye patch or filter. Covering one eye helps with double-vision by blocking input to one eye. Your provider might recommend wearing an eye patch some of the time or all the time, depending on your case. Wearable filters (these often come as attachments you can wear on eyeglasses) that screen out light work similarly.
• OnabotulinumtoxinA injection. OnabotulinumtoxinA can temporarily block signals traveling through treated nerves. Injecting it near certain nerves can help with eye misalignment.
• Strabismus surgery. Several surgical procedures can help with sixth nerve palsy. Some help improve control of the lateral rectus muscle when it’s weaker. Others take part of a muscle from the other side of your eye (which relies on a different nerve for signaling) and reattach it to work like the lateral rectus muscle.
• Prism correction. These can be small, layered attachments worn on the lenses of your eyeglasses, or your eyeglasses’ lenses can be made with prism built into the prescription. A prism effect bends light, and if bent to the correct angle, it can make it easier for your eye to align and see.

Complications/side effects of surgery

Strabismus surgery can sometimes undercorrect or overcorrect for sixth nerve palsy. In cases like this, the difference is often treatable with prism correction, which can make up for an undercorrection or reverse an overcorrection.

How soon after treatment will I feel better?

The recovery time after treatment varies. Your healthcare provider can tell you more about what you should expect in your particular case.

Some treatments work immediately and offer relief from symptoms. Patching is an example of this, as it stops double vision by blocking vision in one eye. Prism correction may also provide quick improvements, but it may take days or weeks — depending on the degree of correction — to fully adjust to the change.

Can sixth nerve palsy be prevented?

Sixth nerve palsy happens unpredictably. The conditions that can cause it don’t always do so, and it often happens for unknown reasons. That means it’s not preventable. You can reduce your risk of developing it from certain causes, though. Examples include:

• Wearing safety equipment as needed. Head injuries, especially concussions and traumatic brain injuries, can lead to sixth nerve palsy. Wearing safety equipment — especially helmets, head-protecting gear and safety restraints like seatbelts — is crucial to preventing this condition.
• Managing your chronic conditions. Some conditions like Type 2 diabetes and high blood pressure are manageable. Your healthcare provider can offer guidance and treatment options, if necessary.
• Don’t ignore infections. See a healthcare provider if you have symptoms of an infection that don’t improve after a few days. Bacterial infections need antibiotics to prevent the infection from getting worse or spreading. But it’s important to remember that antibiotics do nothing for viruses, which should go away on their own or with supportive treatment.

What can I expect if I have sixth nerve palsy?

Sixth nerve palsy isn’t usually dangerous, but it’s still disruptive. It can interfere with school, work, hobbies, social activities and more. It can also feel unpleasant. You might experience dizziness, nausea, headaches and more.

If you experience symptoms of sixth nerve palsy, especially an inability to turn your eyes outward (or in any forward-facing direction), you should talk to a healthcare provider. Most of the time, sixth nerve palsy is a minor concern. But sometimes it happens because of a much more dangerous condition. The best way to increase your odds of a good outcome is to get a diagnosis and treatment sooner rather than later.

How long does sixth nerve palsy last?

Sixth nerve palsy can have a variable duration. Some causes, like migraines, may last only hours. Other causes may last longer, between three and six months. In some cases, it’s a permanent condition. Your healthcare provider is the best person to tell you what’s likely in your case and what you can do to limit how long the condition affects you, or how to adapt to its effects.

What’s the outlook for this condition?

The outlook for sixth nerve palsy is good overall. For most people, it’s a temporary condition that’ll go away on its own or with treatment of the underlying cause(s).

In some cases, though, sixth nerve palsy happens because of more serious conditions. That’s more likely when it happens in someone under age 50, and/or if it affects both eyes. Regardless, it’s always a good idea to get medical care if you have the symptoms of sixth nerve palsy. Earlier diagnosis and treatment can make a difference between a full recovery and long-term (or even permanent) effects.

How do I take care of myself?

If you have sixth nerve palsy, your healthcare provider will guide you on managing it and the condition(s) that cause it (if any are identifiable). It’s important to follow their guidance, particularly when it comes to managing the symptoms. Wearing eye patches, filters or other corrective items is important because it can help you recover faster and minimize unpleasant symptoms.

When should I see my healthcare provider, or when should I seek care?

You should also see your provider as recommended for follow-up visits so they can track any changes and modify your treatment if necessary. Sixth nerve palsy isn’t an emergency, but it is a condition that you should get diagnosed and treated without delay.

What questions should I ask my doctor?

Some questions you may want to ask your healthcare provider include:

• What’s causing my sixth nerve palsy, and are any of the identifiable causes or contributing factors treatable?
• Is it affecting any other cranial nerves or nearby tissues?
• What symptoms should I expect?
• What can I do to minimize my symptoms?
• Are there treatments that might reduce the severity of my current symptoms or speed up my recovery?
• What can I do to prevent a recurrence (keep it from coming back)?

A note from Cleveland Clinic

Sixth nerve palsy is a condition that can disrupt your life, but it’s usually treatable and temporary. However, it’s important to get diagnosed and treated sooner rather than later. Talk to a healthcare provider if you have trouble moving your eyes outward (or in any direction). Doing that can improve the odds of a positive outcome. That way, you can look forward to more important things, rather than have your gaze limited by the effects of this condition.