Duane’s retrobulbar syndrome
What is Duane syndrome?
Duane syndrome, also known as Duane Retraction Syndrome (DRS), is a group of abnormalities in the extraocular muscles that cause abnormal eye movements.
What is normal eye movement like?
The six extraocular muscles that control eye movement are attached to the outside of the eye wall. For each eye, two muscles turn the eye horizontally. The external rectus muscle pulls the eye outward toward the ear, and the internal rectus muscle pulls the eye inward toward the nose. The other four muscles turn the eye upward or downward at an angle. Each extraocular muscle receives its motor commands from the cranial nerves sent by the brain.
What is the cause of Duane’s syndrome?
Duane syndrome is due to a misalignment of the innervation of the extraocular muscles. This “error” may occur around the sixth week of gestation and is due to underdevelopment of the nucleus or a tiny part of the brainstem that controls the abducens of the extraocular muscles.
In Duane’s syndrome, the sixth cranial nerve, which controls the external rectus muscle (the muscle that turns the eye outward), does not develop properly. It is not clear why this nerve is not developing. Thus, the problem is not primarily with the external rectus muscle itself, but with the nerve that transmits electrical impulses to the muscle. There are also irregular nerve impulses from a branch of the third cranial nerve, which controls the medial rectus muscle (the muscle that turns the eye inward). This is the reason why both left and right gaze are abnormal.
Who is at risk for Duane syndrome?
Girls are more likely to develop Duane syndrome than boys. In addition, the left eye is more likely to be involved than the right eye. The cause of this condition is not known. About 20% of people with Duane syndrome have involvement of both eyes. There is no particular race or ethnicity that is more susceptible.
What are the other features of Duane syndrome?
Strabismus – the eyes are not properly positioned, always pointing in different directions.
Head position – the patient often maintains an abnormal head position or face turn to keep the eye in a positive position.
Amblyopia – a loss of vision in the affected eye.
Narrowing of the lid fissure – the affected eye looks smaller than the contralateral eye.
Upward or downward projection – the eye is sometimes deflected upward or downward during certain eye movement states.
Is Duane syndrome congenital (present at birth)?
Duane regression syndrome is present at birth, even though it may not be detected in infancy. The abnormal head position and strabismus are often seen in old photographs taken in early childhood.
Is Duane syndrome hereditary?
In 90% of cases, there is no family history of Duane syndrome. 10% of patients will have another family member involved, and these patients are prone to bilateral eye involvement. Currently, there are no trials to determine if a patient has a genetic form.
Are there different types of Duane syndrome?
The primary characteristic of Duane syndrome is often the inability to rotate the affected eye externally (type 1), internally (type 2), or both (type 3). type 1 is the most common type of Duane syndrome.
Do people with Duane’s syndrome have other eye problems?
Problems with the sixth cranial nerve are usually isolated conditions, and the child is usually completely normal in all other respects. With careful follow-up, the long-term prognosis for vision is usually very good.
Occasionally, Duane syndrome can be combined with other ocular problems, including abnormalities of other cranial nerves, nystagmus (an involuntary back and forth movement of the eye), cataracts, optic nerve abnormalities, microphthalmia (abnormally small eyes), and crocodile tears.
Do patients with Duane syndrome have medical problems outside of the eye?
Problems with the cranial nerves are usually a separate condition, other than that, the child is completely normal. However, some patients with Duane syndrome have other problems, such as hearing impairment, Goldenhar syndrome, and abnormalities of the spine and muscle cones. Intrauterine exposure to thalidomide also increases the chances of Duane syndrome.
When does Duane syndrome require treatment?
For most patients, Duane syndrome does not require surgical treatment. Any of the following 4 items are indications for surgical treatment of Duane syndrome
・ Reduction of strabismus
・ Elimination of head position that interferes with social interaction
・ Elimination of significant upward or downward projection
・ Elimination of inversion of the eye that affects appearance
The goal of treatment is to restore a satisfactory orthoanterior eye position, eliminate abnormal head position and prevent amblyopia. In most cases, surgery of the extraocular muscles is required. Because the function of the involved nerve and muscle cannot be restored, other extraocular muscles are adjusted to compensate and to obtain a better eye position.
To what extent can surgery treat Duane’s syndrome?
Surgery cannot repair the misaligned innervated nerve. By moving the extraocular muscles, surgery can compensate for the misaligned nerve (the result). Because surgery does not “really” fix the problem, it cannot restore normal eye movement, but it can (and usually does) significantly improve the condition. The full effect of the surgery may take a few weeks to manifest. Unexpected results or inadequate correction are less likely to occur. Cutting-edge treatments for Duane syndrome are currently being performed by doctors such as Dr. Hunter at Harvard University Children’s Hospital.