This is a congenital ocular motility disorder. Can you identify, the motility disorder and the underlying syndrome ?
Ans: Duane's syndrome affecting CN 6 on left side Explanation - On left lateral gaze, left eye fails to abduct and the mother reports the problem to be present from as long as she can remember. In addition the taste sensation is impaired and both these symptoms add up to Duane's syndrome. Duane's syndrome in brief Duane's syndrome (DS) is a 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 taste. Other names for this condition include: Duane's Retraction Syndrome (or DR syndrome), Eye Retraction Syndrome, Sausage Eye, Retraction Syndrome, Congenital retraction syndrome and Stilling-Turk-Duane Syndrome. As described by Duane, the characteristic features of the syndrome are: Limitation of abduction (outward movement) of the affected eye. Less marked limitation of adduction (inward movement) of the same eye. Retraction of the eyeball into the socket on adduction, with associated narrowing of the palpebral fissure (eye closing) Widening of the palpebral fissure on attempted abduction. (N.B. Mein and Trimble point out that this is "probably of no significance" as the phenomenon also occurs in other conditions in which abduction is limited). Poor convergence A face turn to the side of the affected eye to compensate for the movement limitations of the eye(s) and to maintain binocular vision. Eye is 45ﾟ to left or right, resulting in "correct movement", but wrong placing of eye. (i.e. when an unaffected eye looks to the right, the affected eye looks straight forward, and when the unaffected eye looks straight forward, the affected eye looks to the left) Cause Alexandrakis G & Saunders RA 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. 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. Differential Diagnosis 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. 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). Ref - Wiki Credit to Dr. lakmalDJ and Dr. EM Mike for solving the challenge.
