Duane Syndrome with Exotropia

Primary gaze position exotropia is rare in children with Duane syndrome. It is a progressive condition that becomes symptomatic in older adults when the degree of exotropia cannot be comfortably compensated by a face turn. In the setting of a large-angle exotropia, Duane syndrome often goes unrecognized because the adduction limitation may be attributed to a secondary lateral rectus muscle contracture. The clue to the diagnosis lies in the seemingly paradoxical finding of limited abduction in a patient with large-angle exotropia. This scenario exemplifies the importance of distinguishing the position of the globe (which may merely reflect muscle tightness) from the contractility of the muscles. Surgery usually consists of large (as much as 15 mm from the insertion) unilateral or bilateral lateral rectus recessions.38 The usual dose–response curve of millimeters of surgery to diopters of correction does not apply to Duane syndrome due to the combination of contracture and cocontraction. Patients must be forewarned that, although the position of the eye will be transferred to primary gaze, the eye will be unable to move laterally following surgery. Due to the propensity of the lateral rectus muscle to undergo progressive contracture in all exotropic patients, recurrences and undercorrections are common.

There are several options in the surgical management of upshoot or downshoot on adduction. The lateral and medial rectus muscles can both be recessed, decreasing the amount of force on the eye in adduction, allowing the muscle to stay on the main arc of the eye.574 The distal lateral rectus muscle can be longitudinally split, with the upper and lower segments reattached above and below the horizontal main arc of the eye, making it impossible for the globe to slip over or under the lateral muscle when it cocontracts.302 Alternatively, a posterior fixation suture of the lateral rectus muscle may be used to prevent the eye from slipping above or below the cocontracting horizontal rectus muscles.574 Lateral rectus muscle fixation to the orbital wall has been used to treat Duane syndrome with exotropia and effectively eliminates upshoots and downshoots.69,564

Bilateral Duane Syndrome

Surgical repair of bilateral Duane syndrome with esotropia is especially problematic because of the presence of bilateral cocontraction. In this setting, even moderate (5 mm) bimedial recessions may produce a medial rectus “fixation duress” in the fixating eye while at the same time unleashing the cocontracting lateral rectus muscle in the nonfixating eye, leading to a large consecutive exotropia.251 It is usually necessary to

decrease the size of the medial rectus recession from those provided by standard dose–response formulas. Large lateral rectus recessions for Duane syndrome with exotropia can simultaneously treat upshoots and downshoots.

Management of Sixth Nerve Palsy

Children with sixth nerve palsy from head trauma should be observed for 6 months prior to surgical intervention because most recover spontaneously. Sixth nerve palsy in children is associated with a high rate of permanent strabismus and amblyopia.20 For children in the amblyogenic age range, we utilize part-time occlusion of the fixating (usually nonparetic) eye to prevent amblyopia or treat it if it has already developed. This therapy also stimulates abduction of the paretic eye, thereby minimizing the chance of contracture formation. Patching the unaffected eye also stimulates maximal inhibition of the medial rectus muscle to establish the most appropriate head position possible, thus minimizing the potential for a secondary medial rectus contracture to develop.502 Prisms are rarely helpful in the recovery phase due to the horizontal incomitancy of the deviation. The indications for botulinum injection for acute sixth nerve palsy in children are controversial.363 We reserve medial rectus botulinum injection for children with a severe palsy who would have to assume an uncomfortably large face turn to fixate with the paretic eye. It has not been found to be efficacious in children with sixth nerve palsy secondary to brain tumors.272 Its long-term superiority over simple observation has not been documented.

Residual esodeviations in children with sixth nerve palsy can result from incomplete neural recovery, from a medial rectus contracture, or both. Children who show incomplete recovery after 6 months with residual esodeviations in primary gaze are generally treated with strabismus surgery. Surgical treatment in sixth nerve palsy is predicated on the degree of lateral rectus function. Visible abduction past the midline demonstrates the presence of residual lateral rectus function and suggests that a recess–resect procedure will be sufficient to restore ocular alignment. As in Duane syndrome, it is often helpful to perform an additional medial rectus recession and/or a medial rectus posterior fixation suture of the contralateral medial rectus muscle to create a fixation duress to “drive the palsy.” This procedure improves abduction of the paretic eye and leads to a larger postoperative field of single binocular vision.

Absence of abduction past midline indicates either a lateral rectus paralysis or severe medial rectus contracture with some lateral rectus function. In this circumstance, the surgical decision is predicated on the clinical estimation or