Duane retraction syndrome 1
Overview
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.
Causes
DS 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.[2] Alexandrakis G & Saunders RA [4] 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 abnormalities 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
Treatment
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).