Duane Syndrome

Duane syndrome — which is also known as Duane’s syndrome or Duane retraction syndrome — is a rare form of strabismus, or misalignment of the eye. Where most forms of strabismus leave side-to-side eye movements intact, in Duane syndrome the “wiring” of the eye muscles gets jumbled, and movement of eye(s) is limited in certain directions. There are three types of Duane syndrome, but the most common is Type I, which interferes with the eye’s ability to move outward (away from the nose). Duane syndrome usually affects just one eye, but it can sometimes involve both. The left eye is more likely to be affected than the right, although doctors still don’t know exactly why.

To better understand Duane syndrome, it’s helpful to understand the basic anatomy of the eye.

• Three of the nerves extending from the brain to the eye muscles, called cranial nerves, control the movements of the eye by transmitting electrical signals.
• The sixth cranial nerve is in charge of the lateral rectus muscle, the muscle that moves the eye outward.
• The third cranial nerve controls the medial rectus muscle, the muscle that pulls the eye inward, as well as other muscles.

There are three types of Duane syndrome. In all three types, the opening of the eye narrows and the eyeball retracts when the eye moves inward.

By far the most common is Type I, in which, in addition to the retraction of the eye:

• There is limited or no ability to move the eye outward
• The eye has little to no difficulty moving inward
• The opening of the eye and widens when the person tries to move the eye outward

In Type II Duane syndrome:

• There is limited or no ability to move the eye inward
• The eye has little to no difficulty moving outward

In Type III Duane syndrome:

• There limited or no ability to move the eye either inward or outward

Because the affected sixth cranial nerve cannot be repaired or replaced, there is no cure for Duane syndrome. However, for people whose lives are significantly disrupted by the condition, surgery can be very helpful in:

• Reducing or stopping the abnormal head posture many develop in an attempt to see better
• Reducing the angle of strabismus

Duane syndrome occurs when the sixth cranial nerve — the nerve originating in the brainstem that controls the movements of the lateral rectus muscle — either doesn’t develop at all, or doesn’t work properly.

If there is no nerve to carry the signal from the brain to the muscle:

• It is like having no wire between the light switch and the light bulb — nothing happens.
• Instead, the nerve that is supposed to control the opposite muscle, the medial rectus muscle, sends an extra branch to activate the lateral rectus muscle.

But with this jumbled wiring:

• The lateral rectus muscle tries to pull the eye outward when the brain is telling the medial rectus muscle pull the eye inward.
• As a result, the two muscles end up in a tug of war that causes the eye to retract partially into the eye socket as the medial rectus muscle overcomes the lateral rectus muscle to pull the eye inward.
• This is why some people call the condition “Duane retraction syndrome,” and retraction of the eye during attempted inward movement is the hallmark of the diagnosis.

In some people, the lateral rectus muscle overcomes the medial rectus muscle in the tug of war, and the eye can move outward but not inward (Duane syndrome Type II). In other cases, neither the lateral nor the medial rectus muscle dominates, and the eye does not move well either inward or outward (Duane syndrome Type III).

Children with Duane syndrome are born with the disorder. However, it might not become readily apparent until the child grows older and starts demonstrating difficulty with vision or an abnormal head turn to the side. Most cases of Duane syndrome are diagnosed by age 10.

Ninety percent of children with Duane syndrome have no family history of the disorder. About 5 percent of people with Duane syndrome have a parent with Duane syndrome (dominant inheritance). Our research team has discovered the CHN1 mutation in patients with dominantly inherited Duane syndrome. There is currently no test available that can detect a genetic marker for the disorder, except for the CHN1 genetic test when Duane syndrome affects more than one generation in a family.

Although Duane syndrome is congenital (present at birth), it may take as long as several years for it to become noticeable: very young children cannot vocalize the fact that they are having trouble with their vision, while older children may have learned to compensate very well for their visual difficulties. In both cases, the symptoms children show can be quite subtle. Most people with Duane syndrome are diagnosed by age 10.

When symptoms are noticeable, they usually include:

• Holding the head in an abnormal posture, turned to the right or left
• Crossing or misalignment of the eyes
• Closing one eye to see better

Older children may be able to describe the problems they are experiencing, such as:

• Double vision
• Neck pain
• Headaches
• Difficulty seeing things on the side of the affected eye

Since these symptoms can also be caused by other eye disorders, it’s important to obtain an evaluation from a qualified eye doctor as soon as possible.

A pediatric eye specialist can diagnose Duane syndrome by:

• Obtaining a complete medical and family history
• Conducting a full medical exam and vision exam
• Measuring the degree of misalignment in the eyes
• Testing the range of movement of both eyes
• Determining whether an abnormal head turn is used in an attempt to see better

In addition, the doctor may recommend referral to a primary care doctor or specialist to check for possible disorders associated with Duane syndrome by examining these areas:

• Spine
• Neck
• Hands
• Hearing
• Palate (the roof of the mouth)

The exact course of treatment will be determined by:

• Age
• Type of Duane syndrome
• Whether there are any related disorders
• Specific symptoms
• Family preferences

Many people with Duane syndrome don't have any symptoms that interfere with their day-to-day lives. There is no obvious misalignment of the eyes, and patients may be able to compensate for their lost or reduced eye movement with just a slight head turn. These people may need nothing more than long-term monitoring by their eye doctor.

Children whose symptoms are more severe — for example, people with a serious degree of eye misalignment, or those who can't see normally without turning their heads to the side — may need eye muscle surgery. Though no surgery can fix the improperly developed cranial nerve that is causing the limited motion in the eye muscle, doctors can use surgery to reposition the other eye muscles — allowing them to work better and keep the eyes in better alignment.

Your treating clinician will work with you to determine the best next steps for your child's particular circumstances.

Boston Children's Hospital is known nationwide for handling the most complex cases of Duane syndrome and related disorders. Our ophthalmologic surgeons specialize in the delicate eye muscle operations that are required to treat the syndrome, including adjustable suture surgery and vertical transposition surgery.

Our ophthalmologists are actively involved in research that is shaping the way eye disorders like Duane syndrome are detected and treated around the world. And, since we are Harvard Medical School’s primary teaching hospital for pediatrics and pediatric ophthalmology, our doctors are also training the next generation of clinicians and clinical scientists.

Our team treats each person with Duane syndrome with a patient-focused, family centered approach, drawing from the extensive multidisciplinary expertise within our Department of Ophthalmology and across the hospital.

Although we are known for our science-driven approach to medicine, we always remember that every patient is, first and foremost, an individual. Our team of professionals will create a customized treatment plan for specific symptoms and circumstances — and we’ll include you and your family at every step of the way.