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Duane syndrome (DS) is a rare, congenital eye movement disorder most commonly characterized by the inability of the eye to turn out. The syndrome was first described by Jakob Stilling (1887) and Siegmund Türk (1896), and subsequently named for Alexander Duane who discussed the disorder in more detail in 1905
Other names for this condition include: Duane's Retraction Syndrome (or DR syndrome), Eye Retraction Syndrome, Retraction Syndrome, Congenital retraction syndrome and Stilling-Turk-Duane Syndrome.
As described by Duane, the characteristic features of the syndrome are:
In about 80 per cent of cases, only one eye is affected, most often the left. However, in some cases, both eyes are affected, with one eye usually more affected than the other.
Causes state that:
In most cases, the abducens nucleus and nerve are absent or hypoplastic, and the lateral rectus muscle is innervated by a branch of the oculomotor nerve. However, there may be contributing mechanical abnormalitiesThis view is supported by the earlier work of Hotchkiss et al who reported on the autopsy findings of two patients with Duanes syndrome. In both cases the sixth cranial nerve nucleus was absent, as was the sixth nerve, and the lateral rectus muscle was innervated by the inferior division of the third or oculomotor cranial nerve. This misdirection of nerve fibres results in opposing muscles being innervated by the same nerve. Thus, on attempted abduction, stimulation of the lateral rectus via the oculomotor nerve will be accompanied by stimulation of the opposing medial rectus via the same nerve; a muscle which works to adduct the eye. Thus, co-contraction of the muscles takes place, limiting the amount of movement achievable and also resulting in retraction of the eye into the socket.
The mechanical factors noted by Miller and Clark above are generally regarded as arising secondary to loss of innervation. During corrective surgery fibrous attachments have been found connecting the horizontal recti and the orbital walls and fibrosis of the lateral rectus has been confirmed by biopsy. This fibrosis can result in the lateral rectus being 'tight' and acting as a tether or leash. Co-contraction of the medial and lateral recti allows the globe to slip up or down under the tight lateral rectus producing the up and down shoots characteristic of the condition.
Most patients are diagnosed by the age of 10 years and DS is more common in girls (60 percent of the cases) than boys (40 percent of the cases). A recent french study  reports the following findings:
The incidence of this syndrome in the population of strabismic patients was 1.9%. The number of women affected was 83 (53.5%). The syndrome was unilateral in 121 cases (78.1%). The left eye (71.9%) was affected more frequently than the right.Around 10-20% of cases are familial; these are more likely to be bilateral than non-familial Duane syndrome. Duane syndrome has no particular race predilection. While usually isolated to the eye abnormalities, Duane syndrome can be associated with extraocular problems (so-called "Duane's Plus"), including cervical spine abnormalities (Klippel-Feil syndrome), Goldenhar syndrome, autism, heterochromia,and thalidomide-induced embryopathy.
Brown classified the condition using the following three sub-types, based upon clinical observations:
Huber's classification system was based upon electromyographical examinations:
Disorders similar in presentation to Duane syndrome can be acquired as a result of trauma, or following localised infection of the orbit leading to inflammation and consequent mechanical restrictions of eye movement. In such cases a full case history will usually help in distinguishing between these conditions. In the clinical setting, the principal difficulties in differential diagnosis arise as a consequence of the very early age at which patients with this condition first present. The clinician must be persistent in examining abduction and adduction, and in looking for any associated palpebral fissure changes or head postures, when attempting to determine whether what often presents as a common childhood squint is in fact Duane syndrome. Fissure changes, and the other associated characteristics of Duane's such as up or down shoots and globe retraction, are also vital when deciding whether any abduction limitation is the result of Duane's and not a consequence of VI or abducens cranial nerve palsy.
The majority of patients remain symptom free and able to maintain binocularity with only a slight face turn. Amblyopia is uncommon and, where present, rarely dense. This can be treated with occlusion, and any refractive error can also be corrected.
Duane syndrome cannot be cured, as the "missing" cranial nerve cannot be replaced and, traditionally there has been no expectation that surgery will result in any increase in the range of eye movement. Surgical intervention, therefore, has only been recommended where the patient is unable to maintain binocularity, where they are experiencing symptoms, or where they are forced to adopt a cosmetically unsightly or uncomfortable head posture in order to maintain binocularity. The aims of surgery are to place the eye in a more central position and, thus, place the field of binocularity more centrally also, and to overcome or reduce the need for the adoption of an abnormal head posture. Occasionally surgery is not needed during childhood, but becomes appropriate later in life, as head position changes (presumably due to progressive muscle contracture).
In types A and B the most commonly adopted approach remains the recession of the medial recti of the affected eye, or of both eyes where the condition is bilateral. In type C, recession of the lateral recti is the method of choice.
Dr. Arthur Rosenbaum at UCLA has championed the use of Vertical Rectus Transposition sugery.  He reports significant increases in lateral eye movements in many cases. The VRT realigned muscles work with the good medial muscle to provide a "tripod" of musculature for the eye; the newly moved muscles provide torque and tension against the medial muscle, which is what allows for the central alignment. And, because they are "working" muscles, they also may allow for some range of lateral movement in their new positions. Morad et al  report the use of a similar approach in Duane's Type C.
Prominent down- or upshoots (such as that pictured above) may be treated with a special form of muscle surgery, a "Y-splitting" procedure, often combined with a recession.
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Duane_syndrome". A list of authors is available in Wikipedia.|