Ординатура / Офтальмология / Английские материалы / Handbook of Pediatric Strabismus and Amblyopia_Wright, Spiegel, Thompson_2006

the anteriorization procedure has become popular, as results have been good even in cases of severe overaction. Anteriorization works by transposing the inferior oblique insertion from its normal position posterior to the equator of the eye to a position anterior to the equator. When the inferior oblique insertion is anterior to the equator, the inferior oblique muscle no longer acts as an elevator but, instead, pulls the front of the eye down; now, it is actually a depressor. This change is why anteriorization procedures that place the inferior oblique muscle anterior to the inferior rectus insertion can cause the complication of an ipsilateral hypodeviation and limited elevation.4,33 This complication can be avoided by keeping the anterior inferior oblique muscle fibers posterior to the inferior rectus insertion. Keeping the posterior fibers of the inferior oblique muscle at least 3 mm posterior to the inferior rectus insertion is especially important because of the inferior oblique neurovascular bundle.34,35 The neurovascular bundle is a relatively inelastic structure inserting in the posterior aspect of the inferior oblique muscle. If the posterior fibers are anteriorized to the level of the inferior rectus insertion, the neurovascular bundle will tighten and act as a tether holding the eye down. Anteriorizing the posterior fibers produces a J-deformity of the inferior oblique insertion. This author prefers avoiding the J-deformity and has developed a graded anterior transposition procedure that keeps the posterior fibers posterior to the anterior fibers. The graded anterior transposition procedure yields excellent results, even in severe cases, without the complication of limited elevation.9 Because the full anteriorization procedure with a J-deformity causes limited elevation, it is rarely indicated. However, it can be considered if performed bilaterally for severe bilateral inferior oblique overaction with a large DVD.

Brown’s Syndrome

ETIOLOGY

Brown’s syndrome is a restrictive strabismus characterized by limitation of elevation that is worse when the eye is in adduction (Fig. 9-10A). It can be congenital or acquired, with a variety of causes for the restriction of elevation in adduction (see Table 9-7). The term congenital Brown’s syndrome or “true” Brown’s syndrome, is used to refer to Brown’s syndrome caused by a congenitally inelastic superior oblique muscle–tendon complex.36

this occurs because the tight posterior tendon fibers prevent the back of the eye from rotating down; therefore, the front of the eye cannot elevate.36 This restriction is a constant limitation and does not improve or resolve on its own. Typically, on clinical examination, there is minimal to no hypotropia in primary position, minimal to no superior oblique overaction, limited elevation in adduction, and divergence (Y-pattern) in upgaze (Fig. 9-10A).36 There is often some limitation of elevation in abduction, but the key is that the limitation is much worse in adduction.36 Limited elevation in abduction can produce pseudoinferior oblique overaction of the fellow eye because of Hering’s law.36 Intorsion on attempted upgaze has been reported.36 Patients with Brown’s syndrome usually have excellent binocular fusion, as they adopt a compensatory chin elevation and a face turn away from the Brown’s eye to maintain fusion. A patient with a right Brown’s syndrome will have a chin elevation and a face turn to the left.

Standard forced-duction testing shows a restriction to elevation in adduction. If the Brown’s syndrome is caused by a tight superior oblique tendon, then Guyton’s exaggerated forcedduction testing of the superior oblique muscle will reveal a restriction to the eye moving up and in.

ACQUIRED BROWN’S SYNDROME

Causes of acquired Brown’s syndrome include pathology of the superior oblique tendon and trochlea and nonsuperior oblique pathology.36 Causes for trochlear or tendon abnormalities include repeat upper eyelid blepharoplasty, sinusitis with peritrochlear inflammation, rheumatoid arthritis, and a superior nasal mass deflecting the course of the superior oblique tendon (e.g., superior nasal glaucoma implant or superior nasal orbital tumor). Inflammatory Brown’s syndrome may be idiopathic primary trochleitis or secondary to sinusitis. Acquired nonsuperior oblique or trochlear causes of limited elevation in adduction include floor fracture, inferior scarring of the globe, fat adherence after inferior oblique muscle surgery, and strabismus surgery with inferior transposition of horizontal rectus muscles (e.g., infraplacement of a lateral rectus resection and medial rectus recession). Furthermore, many patients will develop an acquired Brown’s syndrome of unknown etiology (Table 9-6).

Idiopathic acquired Brown’s syndrome is often intermittent and sometimes associated with a “click” that is felt by the patient in the superior nasal quadrant when the patient looks up and in. In some cases, the click can be heard with a stethoscope placed in the superior nasal quadrant. The cause of the click and limited elevation is not known, but it may represent inflammation or an abnormality of fascial tissue around the superior oblique tendon. If the cause of an acquired Brown’s syndrome is in question, then orbital imaging studies are indicated. In many cases, acquired Brown’s syndrome will spontaneously resolve over several months to even several years. Surgery should only be considered after the patient has been observed for at least 6 months to 1 year.

Another form of acquired Brown’s syndrome is inflammatory Brown’s syndrome, which is associated with superonasal orbital pain and tenderness. It is hypothesized that trochlear or peritrochlear inflammation is the cause. In some cases, inflammatory Brown’s syndrome is associated with a concurrent sinusitis36 or rheumatoid arthritis (rarely). In the majority of cases, however, the cause of the inflammation is unknown.

The treatment of inflammatory Brown’s syndrome includes a trial of systemic nonsteroidal antiinflammatory agents (e.g., indomethacin 25–50 mg TID) or a local steroid injection in the area of the trochlea. A patient diagnosed with acquired Brown’s syndrome of unknown etiology should undergo workup with orbital imaging, as a variety of local or systemic diseases involving the trochlea may cause a Brown’s syndrome. Medical therapy, not surgery, is the treatment of choice for most cases of inflammatory Brown’s syndrome.

CONGENITAL ELEVATION DEFICIT:

DIFFERENTIAL DIAGNOSIS

Congenital causes for limited elevation include double elevator palsy (see Chapter 10), Brown’s syndrome, inferior oblique paresis, and superior oblique overaction. Double elevator palsy can be distinguished by the presence of similar limitation in abduction and adduction, while primary superior oblique overaction and inferior oblique paresis may be more difficult to differentiate because they have a greater elevation deficit in adduction. See Table 10-6 for a comparison of the clinical findings of superior oblique overaction, Brown’s syndrome, and inferior oblique paresis.

SURGICAL INDICATIONS FOR CONGENITAL

BROWN’S SYNDROME

In general, surgery should be considered for Brown’s syndrome if there is a hypodeviation in primary position that causes a significant chin elevation. Patients with a minimal restriction and no significant face turn can be managed conservatively. Except for a few exceptions, surgery should be reserved for children older than 4 years of age; older children are less likely to develop postoperative suppression and amblyopia. Rarely, one may be forced to operate on a child under 4 years of age if the hypodeviation is large enough to disrupt fusion.

SURGERY FOR CONGENITAL BROWN’S SYNDROME

Management of congenital Brown’s syndrome is based on lengthening the superior oblique tendon.39 Procedures such as tenotomy and tenectomy release the restriction but are not controlled, as the cut ends of the tendon can separate widely and result in a superior oblique paresis. In Brown’s syndrome, the superior oblique muscle is not overacting and, therefore, procedures such as tenotomy or tenectomy often result in a secondary superior oblique paresis. In a study by Eustis et al., 85% of Brown’s patients demonstrated some degree of posttenotomy superior oblique paresis, with one-third requiring a second operation.8 Sprunger et al. reported that 50% of their study patients required further surgery caused by an ipsilateral superior oblique paresis after superior oblique tenotomy.32 To address this problem, Parks has previously suggested performing an ipsilateral inferior oblique recession at the same time as the superior oblique tenotomy. This approach, however, results in prolonged underaction of the inferior oblique and a persistence of Brown’s syndrome.

To achieve a controlled elongation of the superior oblique tendon, this author has developed a procedure called the Wright superior oblique tendon expander (see Chapter 11). A segment of retinal silicone band (usually 6.0 mm long) is carefully sutured between the cut ends of the superior oblique tendon, 3 mm nasal to the superior rectus muscle. The initial conjunctival incision, however, is made temporal to the superior rectus muscle. The temporal incision is stretched nasally to expose the nasal aspect of the superior rectus muscle. This maneuver preserves nasal intermuscular septum so the silicone segment does not scar to

sclera. With the capsule floor intact, the silicone is actually placed within the superior oblique tendon capsule. Parks, this author, and others have obtained excellent results using the superior oblique tendon expander. The expander allows for controlled and reversible elongation of the tendon while maintaining the functional integrity of the superior oblique muscle–tendon complex. In trained hands, complications of the procedure are rare, but these include extrusion of silicone and scarring of the silicone to the sclera, causing postoperative limitation of depression. These complications can be limited by meticulous technique and limiting the maximum length of the silicone segment to 7.0 mm. Many now consider the superior oblique silicone tendon expander the procedure of choice for Brown’s syndrome.

RESULTS OF THE SILICONE TENDON EXPANDER

This author has reported his long-term results using the Wright superior oblique silicone tendon expander on patients with severe Brown’s syndrome (see Fig. 9-10A,B).41 Of 15 patients operated on by the author, preoperative limitation of elevation in adduction measured 3 in 1 patient and 4 in 14 patients. Postoperatively, 14 of the 15 patients showed improved motility with 10 patients demonstrating essentially normal versions. The 1 patient who did not improve after the silicone expander had a nonsuperior oblique tendon cause of Brown’s syndrome. The average final result graded on a scale of 1 to 10 (10 being best) was 8.3. Thirteen (13) of 15 patients (87%) achieved a final result score of 7 or better with a single surgery, and an additional patient was corrected with a second surgery providing an overall success rate of 93%. Ten of the 15 patients had at least 11 months follow-up, with 6 of the 10 patients showing a delayed improvement over a 4- to 6-month period. Five patients had more than 5 years follow-up and 4 (80%) had an excellent long-term outcome (final result, 9–10) with a single operation. All 5 patients had a good outcome (final result, 7–10; mean, 9.2) with 1 patient requiring a second surgery. There were no long-term complications, including no extrusions, no restriction of ocular rotations, and no infections.

Stager et al.34 also reported good long-term results; however, in both papers, Wright and Stager emphasized the importance of surgical technique.34,41 Keep the nasal intermuscular septum and the floor of the superior oblique tendon capsule intact. Also,

perform the tenotomy at least 3 mm nasal to the superior rectus muscle to avoid adhesions to the superior rectus muscle. Finally, use 5 to 6 mm of silicone band segment for Brown’s syndrome. Both papers also commented on late improvement after surgery. Some patients showed a significant undercorrection immediately after surgery, but then improved to have excellent result by weeks, to even months, after surgery. The Wright silicone tendon expander is an effective option for correcting Brown’s syndrome, caused by a stiff or inelastic superior oblique tendon, with excellent long-term outcomes. Proper technique with maintenance of the tendon capsule is critical to the successful outcome of the procedure.43

CANINE TOOTH SYNDROME

Scarring in the area of the superior oblique tendon and trochlea will limit movement of the tendon in both directions, resulting in a Brown’s syndrome with a superior oblique paresis. This disorder has been called “Canine tooth syndrome” or Knapp type 7 classification.2,14,15,18,21,43 In this author’s thesis43 on Brown’s syndrome, three patients were diagnosed as having Canine tooth syndrome with both restrictive elevation in adduction and a superior oblique palsy. All three cases presented with penetrating trauma to the trochlear area, two by metal hooks and one from a dog bite. Management of these cases is difficult, as surgery in the area of the trochlea can lead to further scarring and worsening of the condition. In the acute phase immediately after trauma, local corticosteroid injection might help reduce secondary fibrosis.2 Initial management is conservative observation because spontaneous improvement may occur.18 If the deviation persists after 4 to 6 months, then surgical correction can be considered. In these cases, it is best to correct the strabismus by operating on the extraocular muscles rather than trying to remove fibrosis in the trochlear area.43

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