Duane Syndrome Treatment & Management

Standard therapies

Standard management of Duane syndrome (DS) may involve surgery. The goal of surgery is the elimination or improvement of an unacceptable head turn, the elimination or reduction of significant misalignment of the eyes, the reduction of severe retraction, and the improvement of upshoots and downshoots.

Surgery does not eliminate the fundamental abnormality of innervation and no surgical technique has been completely successful in eliminating the abnormal eye movements. Simple horizontal muscle recession procedures, vertical transposition of the rectus muscle, or combinations of the 2 may be successful in improving or eliminating head turns and misalignment of the eyes. ^[21] The choice of procedure must be individualized.

Treatment and interventions

Any treatment is aimed at correcting a notable face turn or strabismus. Special seating may be needed in school to accommodate a child's head turn. Special rear-view mirrors help during driving.

A prism can be placed on the patient's glasses to correct for the face turn (though this is not commonly used).

Vision therapy can be used to treat secondary convergence insufficiency.

Surgery

The success rate in eliminating an abnormal head position is 79-100%. Results are stable for at least 8.75 years after surgery. Surgery does not improve motility. Surgery does not improve stereo or fusion. A risk for diplopia may be present with or without surgery.

The goal of surgery is to correct the face turn, decrease upshoots and downshoots, eliminate globe retraction, and align the eyes in primary position.

Surgery can be done any time, but it usually is deferred until the child can walk.

Consider the patient's motor development (eg, ability to walk or catch a ball).

Types of surgery are as follows:

• Duane syndrome type 1: Recession of the medial rectus (no effect on abduction), posterior fixation suturing on the normal medial rectus (may diminish adduction innervation slightly to the involved eye, decreasing the esodeviation), or resection involving the lateral rectus (but may turn type 1 into a severe type 2).
• Duane syndrome type 2: Recession of the lateral and medial rectus muscles in the involved eye (may need to recess the contralateral lateral rectus if deviation or retraction is severe), or medial rectus recession on the affected side. ^[22]
• Duane syndrome type 3: Recession of the medial and lateral rectus muscles for retraction or an upshoot or downshoot (best for severe cases), Y split of the lateral rectus can reduce retraction upshoot or downshoot, or posterior fixation suturing on the lateral rectus reduces upshoot and downshoot.
• Duane syndrome type 4: Recession of both lateral rectus muscles (larger amount on the involved side than on the uninvolved side), or surgery designed for the unique patient with rare types.

Strabismus surgery can be performed if the patient has a clinically significant anomalous head position.

The results of surgical treatment of the retraction syndrome often have been disappointing. For this reason, surgical intervention is not performed when binocular vision is present with the eyes in primary position or if vision can be maintained with a slight head turn. However, the aberrant innervation in Duane syndrome produces different manifestations, any one of which may require surgery. The clinically significant manifestations include a face turn with strabismus in primary position, an upshoot or downshoot during adduction, vertical deviation in primary position, retraction during adduction, and enophthalmos.

Indications

Although none of the findings listed above is an absolute indication for surgery, the need for surgery depends on the severity of the manifestations and the degree to which patients believe that they are disfigured or functionally compromised (as can be the case with a large face turn). The most common indication for surgical treatment is an unacceptable face turn. The face turn is a secondary manifestation of strabismus in primary position and develops to permit fusion. If it is sufficiently large, the face turn may be disfiguring and functionally debilitating.

Patients who have Duane syndrome with exotropia in primary position usually have a face turn away from the affected eye. Most commonly, esodeviation in primary position leads to a face turn toward the side of the affected eye. This face turn usually is most pronounced with distant fixation. The face turn and measured deviation with near fixation may be minimal, but this situation is not a contraindication to surgery because a procedure designed to fully correct the face turn at a distance generally does not produce secondary overcorrection at near fixation.

On occasion, fusion is impossible in a patient with Duane syndrome, usually because bilateral involvement or a vertical deviation prevents fusion with any head posture. In these cases, the strabismus itself rather than the secondary head posture can be the main indication for surgical correction.

When the affected eye is adducted, an upshoot, downshoot, or retraction can be sufficiently disturbing to the patient or the parents of the patient to warrant surgical treatment. The retraction may be accentuated by the face turn that is seen with the most common esotropic form of Duane syndrome; this places the affected eye in an adducted position. In severe cases, clinically significant enophthalmos and pseudoptosis is present even in primary position. A reduction of 50% or more of the width of the palpebral fissure during adduction compared with primary position has been suggested as an indication for surgical treatment of the retraction.

Contraindications

Many patients with Duane syndrome are orthophoric in primary position or have only an insignificant face turn. In these cases, surgery is not indicated unless another manifestation of Duane syndrome, such as an upshoot or a downshoot, is causing some hardship. The fact that a patient seeks evaluation does not necessarily indicate a desire for surgical correction. Often, it is not the manifestations of the condition themselves that have motivated the consultation, but rather, a concern that they indicate some ominous underlying intracranial disease, especially in parents who bring their child with Duane syndrome to be examined.

If discussion with the patient or the patient's parents reveals that fear of life-threatening disease rather than a manifestation of Duane syndrome is their chief concern, then explanation and reassurance may be all that is needed.

Because fusion can usually be achieved by means of a face turn, most children with Duane syndrome have normal binocular function and stereopsis. Therefore, in distinction to congenital esotropia, for which the goal is to restore ocular alignment as early as possible, the goal in Duane syndrome should be to avoid disrupting normal binocular development. Therefore, a young age is a relative contraindication for surgery.

Severe cases may warrant early treatment, but it usually is preferable to delay surgery until patients are aged 4-5 years. At this age, patient cooperation facilitates detailed examination, and their visual system is relatively mature and less susceptible to damage from a temporary disruption of binocularity than before, as can occur postoperatively if an unfavorable response to surgery occurs.

Procedures

Recession of the medial rectus muscle in the involved eye aligns the eye but does not improve abduction beyond the primary position. In rare cases, large weakening procedures performed on the medial rectus lead to consecutive exotropia because of poorly understood mechanisms. Small medial rectus recession in the opposite eye helps the involved eye in primary position by application of the Hering law.

Resection of the lateral rectus muscle is avoided because it increases retraction and does not improve abduction. Recession of the ipsilateral medial rectus muscle is the mainstay of surgical treatment of Duane syndrome. In patients with esotropia in primary position, this procedure improves the face turn and the esotropia by weakening the antagonist of an effectively paretic lateral rectus muscle.

Medial rectus recession alone may improve the enophthalmos and vertical overshoots in adduction, in part by limiting adduction of the eye. However, additional measures usually are needed to adequately manage these problems if they are severe. To effectively reduce or eliminate the face turn, recession must be larger than that typically performed on a medial rectus muscle, often in the range of 8-10 mm, as measured from the original insertion.

Standard recession or a hang-back technique may be used; this can decrease the difficulty of the procedure when a large recession is needed. When clinically significant mechanical restriction due to contracture or fibrosis of the medial rectus muscle is present, a relatively small recession usually is sufficient. A large recession easily can cripple a fibrotic muscle, which often has contractile properties that are almost as severely compromised as its elastic properties.

For adults with mechanical restriction of the medial rectus muscle, techniques for adjustable-suture recession are helpful for finding the best compromise between adequate relief of the face turn and crippled adduction.

Recession of the contralateral medial rectus muscle in addition to the ipsilateral medial rectus muscle may be performed in cases in which the patient has primary position esotropia greater than 20 diopters and marked co-contraction of the lateral rectus muscle, as shown by limited adduction, massive retraction, or reduced adduction saccadic velocities.

Recessing the contralateral medial rectus muscle may allow for decreased recession of the ipsilateral medial rectus muscle. However, millimeter for millimeter, this procedure is less effective than it is in concomitant esotropia because it is an attempt to treat the large secondary deviation. The ipsilateral medial rectus recession still must be sufficient to permit abduction of the ipsilateral eye to at least midline; otherwise, the addition of a contralateral medial rectus recession, regardless of size, cannot correct the face turn. Recession of the contralateral medial rectus muscle may reduce the long-term risk for contracture of the ipsilateral medial rectus muscle by reducing its tonic innervation (Hering law).

Transposition of the vertical rectus muscles to a position adjacent to the lateral rectus, with or without recession of the ipsilateral medial rectus, has been suggested as a means of correcting the primary position esotropia, of improving abduction, and of enlarging the field of single binocular vision.

This procedure may provide better abduction than that possible with medial rectus recession alone. However, it is more difficult to perform than the other procedure; it may exacerbate retraction, upshoot, or downshoot; it can create new vertical deviations; and, particularly in adults in whom medial rectus recession is performed concurrently, it poses some risk for anterior segment ischemia. This procedure probably should be considered only as primary treatment of patients with no abduction at all, for those with minimal retraction, and for those with no upshoot or downshoot.

Exodeviation in primary position with a face turn away from the side of the affected eye is an uncommon presentation of Duane syndrome. In this case, the face turn is treated with recession of the ipsilateral lateral rectus muscle. In patients who have both primary position exotropia and a marked upshoot or downshoot, a lateral rectus recession usually is combined with an additional measure—either a Y-splitting procedure or a posterior fixation suture—to minimize sideslip of the lateral rectus muscle across the globe.

Recession of the lateral rectus is effective in reducing the upshoot or downshoot during adduction when it is due to sideslip of a tight lateral rectus, particularly if it is combined with recession of the medial rectus. Recession of the lateral rectus muscle alone improves the retraction with adduction somewhat. However, large recessions (10-12 mm) of both the medial and lateral rectus muscles of the ipsilateral eye are effective, particularly when enophthalmos in primary position is a major complaint. As with medial rectus recessions, recessions of the lateral rectus muscles should be decreased when restriction of the lateral rectus muscle is clinically significant.

Co-contraction of the medial and lateral rectus muscles on attempted adduction can cause a striking upshoot or downshoot of the eye. This effect is attributed to sideslip of a tight lateral rectus over the globe (mechanical factors) in most cases.

The Y-splitting procedure effectively results in a broad lateral rectus insertion that stabilizes its position and prevents it from flipping superiorly or inferiorly over the globe, eliminating or greatly reducing the upshoot or downshoot of the affected eye in attempted adduction. The Y-splitting procedure may be combined with a moderate recession of the lateral rectus muscle, particularly if associated primary position exotropia exists.

Placement of a posterior fixation suture on the lateral rectus muscle can effectively prevent slippage of the muscle belly over the globe. This may be used as an alternative procedure to treat upshoots and downshoots. As with the Y-splitting procedure, posterior fixation suturing can be combined with a lateral rectus recession when appropriate.

Besides the mechanical factors discussed above, innervational factors, presumably aberrant co-contraction of the vertical rectus or inferior oblique muscles, may contribute to an upshoot or a downshoot in some patients with Duane syndrome. When vertical deviation in primary position is clinically significant, surgery on the horizontal rectus muscle alone generally does not correct the problem adequately, and recession of the appropriate vertical rectus muscle is needed. The upshoot in adduction that often is seen in Duane syndrome bears some resemblance to inferior oblique overaction, but inferior oblique weakening procedures usually are ineffectual in correcting the problem.

Expected results

Horizontal muscle recession reportedly eliminates the face turn in 79% of patients and substantially reduces the face turn in most of remaining patients. In a patient with esotropic Duane syndrome, recession of the ipsilateral medial rectus muscle usually provides a modest improvement in abduction if some abduction past the midline was present preoperatively; however, this improvement often comes at the expense of some reduction of adduction. The field of single binocular vision is shifted to include primary position but remains relatively unchanged in size.

On the contrary, if the patient does not have abduction past the midline before surgery, medial rectus recession that is sufficiently large to eliminate the primary position esotropia and face turn substantially limit adduction while providing little or no improvement in abduction.

The size of the field of single binocular vision may be reduced under the circumstances just described, though the addition of a contralateral medial rectus recession, possibly with a Faden procedure, may reduce or eliminate the reduction. Vertical rectus transposition may provide improved abduction and enlarge the field of single binocular vision, particularly in patients with problems with the latter. However, no studies have been conducted to directly compare the efficacy of transposition with that of unilateral or bilateral medial rectus recession.

When they are due to mechanical factors, upshoots and downshoots usually can be satisfactorily reduced or eliminated by performing Y-splitting, posterior fixation, or large recessions of both ipsilateral horizontal rectus muscles. In contrast, when the upshoot or downshoot is due to innervational factors, appropriate recession of a vertical rectus muscle eliminates the vertical deviation in primary position, but some vertical deviation usually remains when the eye is adducted. Large recessions of both horizontal rectus muscles usually provide satisfactory correction of enophthalmos in primary position, but some retraction in adduction remains.

Undercorrection of the primary position esotropia and face turn probably is the most common adverse outcome after surgical treatment of Duane syndrome, especially when surgeons use amounts of recession typical of their experience in treating concomitant esotropia.

Undercorrection may be obvious in the immediate postoperative period, or the face turn may reappear years after what initially appeared to be a good result. The face turn presumably is due to contracture of the ipsilateral medial rectus muscle.

Undercorrection can be managed by means of vertical rectus transposition or by means of repeat recession of the medial rectus muscle, if the initial recession was relatively small (< 8 mm). Repeat recession of the medial rectus is necessary if passive duction testing still indicates restriction.

With the large recessions necessary to treat Duane syndrome, overcorrection occasionally occurs. Treatment of this secondary exotropia consists of advancement of the recessed medial rectus muscle or recession of the lateral rectus muscle, particularly if passive ductions indicate tightness of the lateral rectus muscles.

New vertical deviations may result from vertical rectus transposition. This condition is treated with (1) dissection (which involves considerable scar tissue) and recession of the appropriate transposed vertical rectus muscle in the ipsilateral eye, particularly if vertical passive ductions are positive, or (2) recession of the appropriate vertical rectus muscle in the contralateral eye.