What are the other Names for this Condition? (Also known as/Synonyms)

• Duane Anomaly
• Duane Retraction Syndrome (DRS)
• Stilling-Turk-Duane Syndrome

What is Duane Syndrome? (Definition/Background Information)

• Duane Syndrome is a disorder of eye movement. This condition prevents outward movement of the eye (toward the ear), and in some cases may also limit inward eye movement (toward the nose). As the eye moves inward, the eyelids partially close and the eyeball pulls back (retracts) into its socket
• Usually only one eye is affected. Some people with Duane Syndrome develop amblyopia ("lazy eye"), a condition that causes vision loss in the affected eye. Most cases occur without other signs and symptoms
• There are three forms of Duane Syndrome, designated types 1, 2, and 3. The types vary in which eye movements are most severely restricted (inward, outward, or both)
• All three types are characterized by retraction of the eyeball as the eye moves inward and are inherited in an autosomal dominant fashion

(Source: Duane Syndrome; Genetic and Rare Diseases Information Center (GARD) of National Center for Advancing Translational Sciences (NCATS), USA.)

Who gets Duane Syndrome? (Age and Sex Distribution)

• Duane Syndrome is a rare congenital disorder. The presentation of symptoms may occur at birth
• Both males and females may be affected
• Worldwide, individuals of all racial and ethnic groups may be affected

What are the Risk Factors for Duane Syndrome? (Predisposing Factors)

• A positive family history may be an important risk factor, since Duane Syndrome is an inherited condition
• Currently, no other risk factors have been clearly identified for Duane Syndrome

It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases one’s chances of getting a condition compared to an individual without the risk factors. Some risk factors are more important than others.

Also, not having a risk factor does not mean that an individual will not get the condition. It is always important to discuss the effect of risk factors with your healthcare provider.

What are the Causes of Duane Syndrome? (Etiology)

• Given the evidence that Duane Syndrome (DS) results from an absence of the abducens nerve (cranial nerve VI) and aberrant innervation, and that it is associated with other anomalies in some cases, it is thought to result from a disturbance of normal embryonic development by either a genetic or an environmental factor at the time when the cranial nerves and ocular muscles are developing (between the third and sixth week of pregnancy)
• Genetic studies of two large families with DS inherited autosomal dominantly (without associated abnormalities) established that mutations in the CHN1 gene were found to be the cause in these and several other families
• Duane-radial ray syndrome (DRRS), inherited in an autosomal dominant manner, has been shown to be caused by mutations in the SALL4 gene. However, no SALL4 gene mutations were found in 25 sporadic cases of isolated DS (occurring in one individual in a family with no additional abnormalities)
• DS can also be found as part of another complex autosomal recessive disorder (that can include deafness, facial weakness, vascular malformations and leaning difficulties) due to mutations in the HOXA1 gene
• In addition, chromosome studies of individuals with DS and other abnormalities have, in rare cases, shown abnormalities that suggest other locations for genes responsible for causing DS
• The majority of cases of Duane Syndrome are sporadic (occurring in individuals with no history of the condition in the family)
• About 10% of affected individuals appear to have other affected family members. Both autosomal dominant (most commonly) and autosomal recessive forms of Duane Syndrome have been documented. In some families with dominant Duane Syndrome, it has appeared to "skip a generation" (showing reduced penetrance) and it has also been shown to range in severity within the same family (showing variable expressivity)
• Most familial cases are not associated with other anomalies. Given the large percentage of sporadic cases, it seems likely that both genetic and environmental factors play a role in the development of Duane Syndrome amongst affected individuals

(Source: Duane Syndrome; Genetic and Rare Diseases Information Center (GARD) of National Center for Advancing Translational Sciences (NCATS), USA.)

What are the Signs and Symptoms of Duane Syndrome?

Duane Syndrome (DS) is present at birth and is characterized by limitation of horizontal eye movement (a limited ability to move the eye inward toward the nose (adduction), outward toward the ear (abduction), or in both directions). In addition, during adduction, the eyeball pulls in and the eye opening (palpebral fissure) narrows. In some cases, when the eye attempts to look inward, it moves upward or downward.

Duane Syndrome has 3 sub-types, which vary depending on which type of eye movement is most restricted.

• In Duane Syndrome type 1, abduction is limited, but adduction is normal or close to normal. The eye opening narrows and the eyeball retracts into the orbit during adduction, and the reverse occurs during abduction
• In Duane Syndrome type 2, adduction is limited, and abduction is normal or only slightly limited
• In Duane Syndrome type 3, both adduction and abduction are limited

The eyeball retracts during adduction in types 2 and 3. Each of these three types has been further classified into three subgroups designated A, B, and C to describe the eyes when looking straight.

Duane Syndrome is an isolated finding in approximately 70% of cases but may be associated with other abnormalities. Major anomalies that may be associated with DS may affect the skeletal system, ears, eyes, nervous system, and/or the kidneys and urinary tract.

Based on the frequency of symptoms observed, the following information may be noted:

Very frequently present symptoms in 80-99% of the cases:

• Oculomotor nerve palsy
• Short palpebral fissure
• Strabismus

Frequently present symptoms in 30-79% of the cases:

• Abnormal vertebral segmentation and fusion    
• Anteverted nares 
• Blepharophimosis 
• Deeply set eye   
• Low posterior hairline  
• Sensorineural hearing impairment

Occasionally present symptoms in 5-29% of the cases:

• Abnormal form of the vertebral bodies
• Abnormality of cardiovascular system morphology 
• Abnormality of the pupil 
• Absent radius
• Amblyopia 
• Aniridia
• Anorectal anomaly
• Aplasia/hypoplasia of the thumb 
• Blepharospasm
• Brachydactyly   
• Camptodactyly
• Central heterochromia                   
• Chorioretinal coloboma 
• Ectopic kidney 
• Everted lower lip vermilion 
• External ear malformation 
• Facial asymmetry
• Hypopigmented skin patches 
• Hypoplasia of the radius
• Hypoplastic iris stroma
• Iris coloboma 
• Irregular hyperpigmentation 
• Microcephaly 
• Microcornea
• Micrognathia 
• Narrow internal auditory canal
• Nystagmus
• Optic disc hypoplasia
• Patchy hypopigmentation of hair
• Plagiocephaly
• Preauricular skin tag
• Ptosis
• Seizures
• Short neck
• Skeletal muscle atrophy
• Spina bifida occulta 
• Stenosis of the external auditory canal
• Talipes equinovarus 
• Triphalangeal thumb 
• Webbed neck 
• Wide nasal bridge

(Source: Duane Syndrome; Genetic and Rare Diseases Information Center (GARD) of National Center for Advancing Translational Sciences (NCATS), USA.)

How is Duane Syndrome Diagnosed?

Duane Syndrome is diagnosed on the basis of the following information:

• Complete physical examination
• Thorough medical history evaluation
• Assessment of signs and symptoms
• Laboratory tests
• Imaging studies
• Biopsy studies, if necessary

Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis.

What are the possible Complications of Duane Syndrome?

The complications of Duane Syndrome may include:

• Severe deformities
• Walking difficulties
• Neurological impairment

Complications may occur with or without treatment, and in some cases, due to treatment also.

How is Duane Syndrome Treated?

The treatment of Duane Syndrome may involve surgery. The goal of surgery is to eliminate or improve head turn, eliminate or reduce significant misalignment of the eyes, reduce severe retraction (when they eyeball pulls into the socket as the eye moves toward the nose), and improve upshoots and downshoots (when the eye deviates upward or downward with certain eye movements).

No specific surgical technique has been completely successful in eliminating the abnormal eye movements. However, some procedures, used either alone or in combination, may be successful in improving or eliminating head turns and misalignment of the eyes. The choice of procedure varies among affected individuals. The success rate for surgery in eliminating an abnormal head position is estimated to be 79-100%.

The management of Duane Syndrome without surgery may include:

• Special seating in school to accommodate a child's head turn
• Special rear-view mirrors to help during driving
• A prism placed on the individual's glasses to correct for the face turn (though this is not commonly used)
• Vision therapy to treat secondary convergence insufficiency (inability of the eyes to turn towards each other or sustain this position)

(Source: Duane Syndrome; Genetic and Rare Diseases Information Center (GARD) of National Center for Advancing Translational Sciences (NCATS), USA.)

How can Duane Syndrome be Prevented?

Currently, Duane Syndrome may not be preventable, since it is a genetic disorder.

• Genetic testing of the expecting parents (and related family members) and prenatal diagnosis (molecular testing of the fetus during pregnancy) may help in understanding the risks better during pregnancy
• If there is a family history of the condition, then genetic counseling will help assess risks, before planning for a child
• Active research is currently being performed to explore the possibilities for treatment and prevention of inherited and acquired genetic disorders

Regular medical screening at periodic intervals with tests and physical examinations are recommended.

What is the Prognosis of Duane Syndrome? (Outcomes/Resolutions)

• The prognosis of Duane Syndrome is dependent upon the severity of the signs and symptoms and associated complications, if any
• Individuals with mild conditions have better prognosis than those with severe symptoms and complications
• Typically, the prognosis may be assessed on a case-by-case basis

Additional and Relevant Useful Information for Duane Syndrome:

Duane Syndrome may be known by the acronym DRS (Duane Retraction Syndrome)

The following DoveMed website link is a useful resource for additional information:

http://www.dovemed.com/diseases-conditions/rare-disorders/