Brown's syndrome is characterized by limited elevation in adduction, but fairly good elevation of the eye in abduction. Brown's syndrome, previously referred to as "superior oblique tendon sheath syndrome," because Brown postulated a taut tendon sheath as an etiology, is well recognized in both congenital and acquired forms. It is now understood that the tendon sheath is not the cause of the restriction.1 Current thinking postulates congenital Brown's syndrome to be secondary to a taut, inelastic tendon or to limitation of movement of the tendon through the trochlea due to adhesions in the region of a narrowed trochlea.2,3 The syndrome may present in congenital, acquired, permanent, or intermittent forms.
The differential diagnosis includes paralysis of the inferior oblique muscle and orbital trauma.4 A forced duction test should be performed for the diagnosis of Brown's syndrome. A positive forced duction test that shows more evidence of restriction when the eye is retropulsed, putting the superior oblique (SO) muscle on stretch, clearly differentiates Brown's syndrome from paralysis of the inferior oblique muscle.4
If binocular vision is present and there is no abnormal head position, no treatment is necessary. In patients with a minimal restriction and no significant face turn, conservative management is adequate.4 In general, if the involved eye is hypotropic in primary position, with a significant chin elevation, or if there is a significant anomalous head posture, surgery should be considered for Brown's syndrome in an attempt to restore binocular function in primary position.4-6
Surgical treatment of Brown's syndrome is based on weakening of the SO muscle.4,5 Lengthening the SO tendon is another procedure of choice.6 Controlled elongation of the SO tendon can be achieved by applying an "expander."
In this study, the long-term clinical results of the SO silicone tendon expander procedure in a consecutive series of patients with Brown's syndrome are reported.
PATIENTS AND METHODS
Records of 22 eyes of 16 patients with the diagnosis of Brown's syndrome were reviewed between January 1995 and January 2002. The follow-up period was 58.4 months on average (range, 44 to 124 months). The etiology, age at operation, sex, length of the expander, depression quantity in adduction in preoperative and postoperative examinations, deviation angle in primary position in preoperative and postoperative examinations, complications that required a second operation, and follow-up time were recorded.
Preoperative examination included a detailed ocular examination, evaluation Diversions and ductions in the diagnostic positions of gaze, and evaluation of primary position deviation at distance and at near.
Criteria for exclusion were previous SO muscle surgery and previous or concurrent surgery on another extraocular muscle. Brown's syndrome was rated as -4 (marked underaction) to +4 (marked overaction) using the system described by Doughty et al.7
If unilateral Brown's syndrome was evident, surgery included a unilateral SO tendon expander procedure. If bilateral Brown's syndrome was evident, surgery included a bilateral SO tendon expander procedure. All operations were performed by the same surgeon.
The aim of the surgery was to provide binocularity of vision as well as to prevent the physical abnormalities associated with long-term abnormal head position. The surgical criteria were as follows: (1) evident hypotropia of the affected eye in primary position; (2) compensatory head tilt; (3) cosmetically unacceptable limited elevation in adduction.
A forced duction test is performed before the operation, and the diagnosis of Brown's syndrome is confirmed. The operation begins with a temporal conjunctival incision. By placing the conjunctival incision temporal to the superior rectus muscle, then reflecting the incision nasally, the surgeon can keep the floor of the nasal SO tendon capsule and the intermuscular septum intact and prevent adhesion of the silicone implant to the sclera. The SO tendon is cut at approximately 4 mm away from the nasal border of the superior rectus muscle. Care is taken to avoid traumatizing the SO tendon sheath and the intramuscular septum in this step. After dissection of the SO tendon sheath, the tendon is clearly seen. The part of the sheath that touches the sclera is not dissected. A segment of a silicone no. 240 retinal band is inserted between the cut ends of the SO muscle tendon. The length of silicone (5, 6, or 7 mm) is determined by the degree of SO overaction.
Information on patients, including age, etiology, amount of silicone expander applied, and findings on preoperative and postoperative ophthalmologic examinations are presented in Table 1.
Nine of the patients were female, and seven were male. Brown's syndrome was congenital in 11 patients and acquired in 5. A bilateral SO tendon expander procedure was performed on 6 of the 16 patients.
The mean age of patients at surgery was 9.7 years (range, 3.5 to 49 years).
The average follow-up period was 58.4 months.
The silicone expanders were applied as follows: 5 mm in 8 eyes, 6 mm in 10 eyes, and 7 mm in 4 eyes.
Preoperative limitation of elevation in adduction measured -2 in 4 eyes (18.2%), -3 in 14 eyes (63.6%), and -4 in 4 eyes (18.2%). Postoperative limitation of elevation in adduction measured -1 in four eyes (18.2%), -2 in one eye (4.5%), and -3 in two eyes (9.1%).
Two eyes had SO palsy. One of them had -2 depression in adduction (patient 10), and the other eye had -3 (patient 16).
The average of "depression in adduction" was -3.0 preoperatively and -0.3 postoperatively. The preoperative average value for "hypotropia in primary position" was 13.15 prism-diopters (pd). This value was 2.56 pd postoperatively (Fig. 1).
Temporary postoperative complications included inflammation in four eyes (18.2%), granuloma in two eyes (9.1%), and irritation in six eyes (27.2%). These complications were successfully treated with local corticosteroids and oral nonsteroidal anti-inflammatory drugs (Table 2).
The other complications that required surgical intervention were extrusion in one eye (4.5%) [patient 2], undercorrection in one eye (4.5%) [patient 4] , depression limitation in abduction in one eye (4.5%) [patient 9], and SO palsy in two eyes (9.0%) [patients 10 and 16]. In one eye (patient 4) that had undercorrection, the silicone band was removed, and the patient recovered completely. After removal of the silicone expander, the eye that had limitation of elevation in adduction (patient 9) recovered. Recession with an anterior transposition procedure was performed on the inferior oblique muscle of patient 10. The implanted silicone band of one patient (patient 16) was removed (Table 2). Complete improvement occurred 2 to 4 months after reoperation.
Slight esotropia in one case (patient 8) and exotropia in three cases (patients 4, 7, and 15) developed in the postoperative period. Patient 8 recovered from esotropia spontaneously. Patient 15 recovered from exotropia, whereas in patients 4 and 7, exotropia persisted. Diplopia, phoria, and cosmetic problems were not observed in patients with exotropia or esotropia. All other patients were orthophoric in primary position. Head tilt improved in all cases. Cyclotorsional symptoms and downgaze restriction were not seen in any case.
The etiology of Brown's syndrome is multifactorial and includes the following: (1) anomalies of die tendon or trochlea; (2) tightness of the tendon; (3) dyskinesia of the SO tendon of the trochlea; (4) dysgenesis of the SO muscle; (5) secondary defects of the trochlea and SO tendon because of infection or trauma; (6) SO anomalies secondary to anomalies of the inferior oblique muscle itself or of the surrounding area; (7) dysfunction after surgery on the SO tendon; (8) paradoxical innervation; and (9) secondary development of Brown's syndrome because of inferior oblique muscle palsy.4
Taking into account the theories about the cause of Brown's syndrome, many surgical techniques have been proposed to treat the disease.
Recession of the SO muscle is performed to treat Brown's syndrome. The problem with this procedure, however, is that it changes the basic functions of the SO muscle. A recession collapses the broad posterior insertion of the SO tendon and creates a new focal insertion. At this new insertion site, the SO muscle no longer functions as a depressor and abductor, but acts as an elevator and a slight adductor.8 This change in the mechanics of insertion is clinically significant because postoperative limitation of depression has been associated with the recession procedure.8,9
Z-tenotomy lengthens the tendon by partialwidth marginal tenotomies that overlap in the center of the muscle.10 Unfortunately, the cross fibers of the SO tendon are weak and diaphanous; thus, a Ztenotomy often results in an inadvertent complete tenotomy.8,11
With the split lengthening procedure, the SO tendon is split in half for a specified length, the tendon halves are removed from the main tendon, and the two halves are sutured together to lengthen the tendon.12 This procedure can produce a graded lengthening of the tendon; however, it is technically difficult to perform.8
Berke described nasal tenotomy performed through a superior nasal incision.13 Parks recommended performing SO tenotomy nasal to the superior rectus through a superior temporal conjunctival incision.13 With this technique, subsequent SO palsy and inferior oblique overaction can occur.4 In fact, consecutive SO palsy is so prevalent after tenotomy for Brown's syndrome that Eustis and Parks and colleagues suggested performing an ipsilateral inferior oblique recession at the same time as the tenotomy.5,14
Posterior tenectomy is designed to weaken the abduction and depressor functions of the SO muscle while maintaining its incyclotorsion function.15 This procedure consists of a wedge resection of the posterior two-thirds of the SO tendon insertion. Because the anterior tendon fibers are left intact, incyclotorsion function is preserved. This procedure has produced variable results, with a high incidence of undercorrection.16
A technical difficulty associated with both SO recession and posterior tenectomy is isolation of all of the posterior tendon fibers. The temporal side of the SO tendon is extremely broad, extending posteriorly to within 6 mm of the optic nerve. Exposing this broad posterior insertion can be very difficult.
In addition to these procedures, to achieve a controlled elongation of the SO tendon, Wright developed a procedure called the "superior oblique tendon expander."17 This technique may be superior to the other techniques because it causes a quantitative relaxation in the functions of the SO tendon without impairing its functions. This is due to the broad insertion of the muscle that enables it to perform three functions. The tendon fibrils in front of the equator are responsible for the incyclotorsion, and the posterior fibrils are responsible for the depression and adduction.17
Wright reported his long-term results with the silicone tendon expander in patients with severe Brown's syndrome.18 Fifteen patients with severe Brown's syndrome underwent surgery. Of these 15 patients, 14 showed improved motility, with 10 patients demonstrating essentially normal versions. In one patient who did not show improvement, Brown's syndrome was not caused by the SO tendon.18 In our patients, there were no cyclotorsional symptoms after surgery. The functions of the SO were maintained in the eyes postoperatively. The results of our study are concordant with the features of this procedure.
Stager et al. reported that placement of a 5- to 8-mm silicone expander in the tenotomized SO muscle tendon is effective in correcting Brown's syndrome, with a low rate of reoperation.19 Initial undercorrection should not discourage the surgeon because improvement may continue for up to 3 years. This technique reduces the need for either simultaneous or subsequent inferior oblique muscle weakening and represents an advance in the treatment of Brown's syndrome.19 In our study, the average limitation of elevation in adduction decreased to -0.3 after surgery whereas it was -3.0 preoperatively. The results 5 years postoperatively were better than those 6 months postoperatively. Our study supports the finding of late improvement.
Various complications can also occur with this technique, as with all other extraocular muscle procedures. A restrictive downgaze deficit and paretic overcorrection are possible complications of the SO tendon silicone expander operation. Wilson et al. pointed out that diplopia in the reading position developed in two patients with unilateral Brown's syndrome after a SO tendon silicone expander procedure.20 In both cases, forced ductions were positive, indicating a restrictive downgaze deficit. Surgical exploration showed adhesions that prevented the normal sliding of the SO tendon beneath the superior rectus muscle. At reoperation, these authors found adherences between the tendon and the medial margin of the superior rectus muscle. Forced ductions became normal, and downgaze improved after removal of the silicone band.20 In our study, the improvement was less than expected postoperatively in one case (patient 4). Abduction limitation in downgaze and diplopia occurred in one case (patient 9) . However, complete recovery was obtained 2 to 4 months after the removal of the silicone band in these cases. In the early postoperative period, paretic hypercorrection developed in two cases (patients 10 and 16). Improvement was obtained with removal of the expander in one case (patient 16); recession with anterior transposition was performed on the inferior oblique muscle in the other case (patient 10).
Seawright and Gole reported that the SO tendon expander technique should be strongly considered for the treatment of SO overaction associated with "A-pattern" or hypotropia in primary position, because it has a high success rate, excellent longterm outcomes, and a low incidence of postoperative complications.21 Pollard and Greenberg emphasized that the SO tendon expander procedure also works well for unilateral SO overaction caused by inferior oblique palsy.22
Awad et al. performed an SO tendon lengthening procedure, using a 10- to 12-mm-long silicone band on each patient. All patients had hypotropia of 20 pd or greater in primary position. All patients experienced improvement in their severe Brown's syndrome. Postoperative hypotropia in primary position was less than 8 pd in all patients. No patient required further surgery, and no extrusions of the implants were noted.23 In our study, we did not implant expanders as long as the expanders used by Awad et al. Yet, in the long term, satisfactory results have been achieved in our study. Regarding further surgery and extrusion, our results were not as successful as those of Awad et al. One patient had extrusion that required repair, and band extraction had to be applied in three patients.
Pollard and Greenberg reported that in 137 operations on 71 patients, 3 patients had sterile orbital cellulitis successfully treated with steroids. Also, one patient acquired a Brown's syndrome-like condition postoperatively. In these four patients, the subTenon capsule space had been inadvertently entered during surgery. Although this procedure has a very high success rate, special care should be taken with this surgery to avoid entering the sub-Tenon capsule space.22 In our study, we were careful to avoid unnecessary disruption of the intermuscular septum along the nasal border of the superior rectus muscle. Also, the intermuscular septum beneath the SO tendon was preserved to prevent direct contact of the silicone with sclera. Proper technique, with maintenance of the tendon capsule, is critical to the successful outcome of the procedure.
The long-term results with the SO silicone tendon expander in patients with Brown's syndrome are promising. Upward gaze in adduction was obtained in all cases; orthophoria was present in primary position, and the abnormal head position disappeared as well. According to the results of this study, the SO tendon expander procedure is a challenging surgical intervention for the treatment of patients with Brown's syndrome with vertical deviation in primary position.
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