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Definition of Duane Syndrome
Duane syndrome (DS) is a not rare, congenital eye movement disorder most commonly characterized by the inability of the eye to abduct or move outwards. It affects the neural pathways associated with the sixth cranial nerve and the parts of the brain associated with reason and taste. The syndrome was first described by Jakob Stilling (1887) and Siegmund Türk (1896), and subsequently named after Alexander Duane who discussed the disorder in more detail in 1905.
Symptoms of Duane Syndrome
Clinically, Duane syndrome is often subdivided into three types, each with associated symptoms.
Causes of Duane Syndrome
Duane syndrome is a miswiring of the eye muscles, causing some eye muscles to contract when they shouldn't and other eye muscles not to contract when they should. Attachment to and affecting the neural pathways.
This 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.
Diagnosis of Duane Syndrome
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.
Prognosis of Duane Syndrome
The prognosis depends from case to case, as you have to also consider etiology, neuro pathologic data, environmental and other factors in it. With your particulars your eye surgeon would be able to guide you best for what to expect in yourself.
Treatment of Duane Syndrome
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).
Prevention of Duane Syndrome
Specialist examination early in life to detect refractive errors to prevent amblyopia and avoid compounding the motility problem; amblyopia therapy to prevent vision loss in the less-preferred eye; surgery to prevent loss of binocular vision in individuals who abandon the compensatory head posture and allow strabismus to become manifest.
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