Brown syndrome is an ocular motility disorder characterized by limited active and passive eye elevation in adduction.1 Patients with vertical deviation in primary position, compensatory head position, or significant downshoot in adduction (often termed Brown syndrome “plus”) usually require surgical correction, whereas less severe cases are often observed without surgery.2,3 Surgical options for Brown syndrome involve weakening or elongation of the superior oblique tendon by Z-tenotomy,4 tenectomy,5 silicone band tendon lengthening,3 split tendon lengthening,6 or posterior tenectomy.7 Previous publications concerning Brown syndrome often report vertical misalignment and compensatory head posture; however, horizontal misalignment is less commonly reported. The purpose of this study was to analyze the incidence of horizontal misalignment requiring surgical correction in this syndrome.
Patients and Methods
The medical records of all patients who were diagnosed as having congenital Brown syndrome and underwent surgical correction at Schneider Children's Medical Center of Israel between 1998 and 2016 were retrospectively reviewed. The main outcome measure was the presence of preoperative primary position horizontal deviation. The study was approved by the institution's Declaration of Helsinki committee and was performed in adherence to its rules and regulations.
All patients had congenital Brown syndrome meeting its recognized diagnostic criteria, including limitation of active elevation of the eye in adduction with positive forced duction test.8 Patients had surgery for correction of either an abnormal head position or primary position hypotropia. All patients underwent complete ophthalmic and orthoptic examinations preoperatively and postoperatively, including visual acuity measurement, anterior segment examination, and dilated funduscopy. Horizontal and vertical misalignments were recorded at 6 and 1/3 m fixation by cover–uncover and alternate–cover prism tests, ensuring straight head position throughout the examination. Ductions were subjectively measured using a scale ranging from −4 (maximal underaction) to +4 (maximal overaction). The information from the most recent visit before surgery and at the last follow-up appointment were used for analysis, including age, gender, head position, extra-ocular motility, ocular misalignment at distance and near fixation, and surgery performed. Patients with prior surgeries, incomplete records, equivocal findings, or coexisting duction deficits other than limitation of elevation in adduction were excluded from analysis.
Statistical analysis was performed using Prism 7 statistical software (GraphPad Software Inc., San Diego, CA). The paired t test was used to compare ocular misalignment before and after surgery, and Fisher's exact test was performed for analysis of change in compensatory head position following surgery. All statistical tests performed were two-tailed and significance was defined at an alpha level below 5%.
Overall, 19 eyes (8 right and 11 left eyes) of 16 patients (7 males and 9 females) were included in this study (Table 1). Mean age at the time of surgery was 4.2 ± 2.6 years (range: 1 to 9 years) and median follow-up was 9 months (range: 1 month to 11 years). Fourteen patients (88%) had surgery for correction of a compensatory head position, including 8 patients (50%) with a head tilt and 6 patients (38%) with a chin-up position, and 2 patients had surgery for primary position hypotropia. None of the patients had amblyopia preoperatively and postoperatively. Fifty-six percent (n = 9) had primary position horizontal deviation before surgery: 50% (n = 8) exodeviations, ranging from exophoria of 4 prism diopters (PD) to exotropia of 30 PD, and one esotropia of 14 PD. All patients underwent a weakening procedure of the superior oblique tendon, by either Z-tenectomy (81%, n = 13) or suture elongation of the superior oblique tendon (19%, n = 3). Fifty percent (n = 8) had a recession of either one (31%, n = 5) or two (19%, n = 3) muscles to correct the horizontal misalignment. Mean preoperative horizontal deviation (9.3 ± 3.4 PD) decreased significantly following surgery (1.7 ± 1 PD) (P = .001, paired t test). There was complete elimination of abnormal head posture in all patients postoperatively (P = .025, Fisher's exact test).
In this study, we found that 50% of patients undergoing surgery for correction of congenital Brown syndrome had significant primary position horizontal misalignment (usually exotropia) requiring surgical correction.
Previous studies on Brown syndrome did not focus on horizontal deviations or commented on consideration of its surgical correction. Stager et al.3 reported on 19 patients with Brown syndrome who underwent expansion of the superior oblique tendon with a silicone band. Five of them (26%) had preoperative horizontal deviation, including four esodeviations of up to 25 PD and one exodeviation of 8 PD, and 4 had concurrent horizontal rectus muscle surgery, but no information was provided regarding the procedures performed. Yazdian et al.9 reported that 4 of 25 (16%) patients with Brown syndrome underwent horizontal rectus muscle surgery for correction of horizontal strabismus in addition to superior oblique weakening; however, no further details were provided regarding the type and extent of the deviations or the procedures performed. Cho et al.10 reported an even higher percentage of horizontal deviations in Brown syndrome, recording that 12 of 15 patients (80%) in their study had horizontal misalignment; 47% (7 of 15) exodeviations of 10 to 30 PD and 33% (5 of 15) esodeviations of 8 to 20 PD.10 Fifty-four percent (8 of 15) of patients underwent horizontal rectus muscle surgery in addition to superior oblique tendon weakening. Similarly, in our study, 8 of 16 (50%) patients with congenital Brown syndrome had significant primary position misalignment, most commonly exotropia (up to 30 PD), requiring surgical correction.
In other studies of patients with Brown syndrome, surgery was limited to the superior oblique muscle, even when a horizontal deviation was present. Mogadham et al.6 described 14 patients with Brown syndrome, of whom 50% (7 of 14) had exodeviations of 10 to 20 PD and 14% (2 of 14) had esodeviations of 12 to 15 PD; however, none of these deviations were corrected at the time of surgery. Sekeroglu et al.11 described 44 patients with Brown syndrome, 32% (14 of 44) of whom had horizontal deviations, including 18% (8 of 44) exotropias and 14% (6 of 44) esotropias. No data were provided regarding surgical correction of these deviations, although the median horizontal distance deviation was 20 PD (range: 4 to 50 PD).
The pathogenesis of horizontal misalignment in Brown syndrome is difficult to explain, especially esotropia. It is possible that contraction of the inferior oblique muscle in an attempt to overcome the restrictive limitation of elevation in adduction leads to abduction of the eye and secondarily to an exo-deviation. In our study, exodeviations were found much more commonly than esodeviations. Another possible mechanism includes a presence of a restrictive fibrotic band in Brown syndrome as previously reported by Parks and Brown.12 Because of the close anatomical proximity of the superior oblique tendon and the lateral rectus muscle, it is possible that this fibrotic band involves both of these muscles, thus explaining a greater likelihood of developing an exodeviation.
Considering the possible effect of ocular misalignment, especially horizontal strabismus, on amblyopia development, it is interesting to note that amblyopia is seldom reported in Brown syndrome. Sekeroglu et al.11 reported that 16% of patients with Brown syndrome had amblyopia at initial presentation. However, the correlation between the amblyopic eye and the involved eye with the motility dysfunction was low and presence of primary position ocular misalignment was found to be a poor predictor of amblyopia development. In addition, many of their patients had refractive amblyopia due to anisometropia, which might not be related to the ocular motility limitation. In our study, none of the patients had amblyopia, even when large horizontal deviations were present preoperatively. This can be explained by surgical correction of ocular misalignment at a relatively young age (average 4 years) and predominance of exodeviations, which are known to be less frequently associated with amblyopia development.
The results of this study should be interpreted within the context of its limitations. This was a retrospective record review and is subject to the selection and follow-up bias inherent to all retrospective reviews. Because of the nature of this study and the young age of most patients at the time of surgery, we failed to secure documentation of stereopsis in all patients. Finally, we only reviewed patients undergoing surgical correction; therefore, our results may not be applicable to patients with less severe Brown syndrome who are treated conservatively.
Significant horizontal misalignment is often present in patients with congenital Brown syndrome, and its correction should be considered at the time of surgery.
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- Stager DR Jr, Parks MM, Stager DR Sr, Pesheva M. Long-term results of silicone expander for moderate and severe Brown syndrome (Brown syndrome “plus”). J AAPOS. 1999;3:328–332. doi:10.1016/S1091-8531(99)70039-X [CrossRef]
- Crawford JS. Surgical treatment of true Brown's syndrome. Am J Ophthalmol. 1976;81:289–295. doi:10.1016/0002-9394(76)90242-7 [CrossRef]
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|Case||Age (y)||Gender||Eye||Preop CHP||Preop Deviation Distance (PD)||Postop CHP||Postop Deviation Distance (PD)||Superior Oblique Surgery||Horizontal Muscle Surgery||Follow-up (m)|
|1a||5||F||BE||Chin up||H = 0, XT = 35||No||H = 0, ET = 2||BSO Z-tenectomy||BLR recession 6 mm||19|
|2||3||F||BE||Chin up||H = 0||No||H = 0, X = 1||RSO Z-tenectomy||None||52|
|3a||8||M||RE||No||RHoT = 6, XT = 16||No||H = 0, XT = 14||RSO Z-tenectomy||LLR recession 6 mm||56|
|4a||M||LE||Chin up||LHoT = 6, XT = 30||No||H = 0, XT = 10||LSO Z-tenectomy||BLR recession 7 mm||1|
|5a||10||M||LE||No||LHoT = 6, ET = 10||No||H = 0, E = 1||LSO tendon suture elongation||LMR recession 5 mm||37|
|6||4||M||LE||L head tilt||LHoT = 15||No||H = 0||LSO tendon suture elongation||None||1|
|7||6||M||RE||Chin up||RHoT = 6, XT = 4||No||RHoT = 3||RSO Z-tenectomy||None||10|
|8||4||F||LE||L head tilt||LHoT = 10||No||H = 0||LSO Z-tenectomy||None||36|
|9a||2||F||LE||L head tilt||RHoT = 10, XT = 20||No||H = 0||LSO Z-tenectomy||LLR recession 8 mm||39|
|10||1||F||LE||L head tilt||LHoT = 10||No||H = 0||LSO Z-tenectomy||None||6|
|11a||4||F||RE||R head tilt||RHoT = 18, XT = 14||No||RHoT = 3||RSO Z-tenectomy||RLR recession 5.5 mm||9|
|12a||2||M||LE||L head tilt||H = 0, XT = 15||No||H = 0||LSO Z-tenectomy||BLR recession 6 mm||2|
|13a||3||F||BE||Chin up||H = 0, XT = 25||No||H = 0||BSO Z-tenectomy||BLR recession 6.5 mm||135|
|14||3||M||LE||R head tilt||LHoT = 10||No||LHoT = 4, E = 2||LSO tendon suture elongation||None||10|
|15||2||F||RE||Chin up||H = 0||No||H = 0||RSO tendon suture elongation||None||5|
|16||8||F||RE||L head tilt||RHoT = 10||No||RHoT = 2||RSO Z-tenectomy||None||5|