Summary
Brown’s syndrome, a rare congenital or acquired form of superior oblique tendon dysfunction, presents as difficulty elevating or inability to elevate the affected eye upon adduction. A pediatric disease by nature, diagnosis is made through clinical observation, deviation measurements with prism diopters, and forced duction testing. Acquired conditions may spontaneously resolve with age in most cases; however, some congenital cases may be severe enough to warrant surgery. Evolution of surgical treatment has advanced from uncontrolled tenotomy to methodical suture spacing, with increasing reports of favorable outcomes. Acquired cases may be further addressed by treating the underlying condition.
10 Brown’s Syndrome
10.1 Introduction
Brown’s syndrome, also known as superior oblique (SO) tendon sheath syndrome, is a relatively uncommon form of restrictive vertical strabismus that may present congenitally or from acquired etiologies and may be unilateral or bilateral. First characterized by H. W. Brown in 1950, the pathophysiology of this eponymously named condition is contingent on a restricted SO trochlea-tendon complex. 1
Incidence in the United States and worldwide averages to 1 in 400 to 450 new strabismus cases and may carry an underlying genetic component manifesting from first-degree family members. 2 , 3 Ten percent of cases are bilateral with a 3:2 female predilection, and the disease affects right eyes more often than left. 4
10.2 Clinical Features
10.2.1 History
Children with Brown’s syndrome have difficulty elevating or are unable to elevate the affected eye(s) upon adduction. Compensatory head turn or chin up head posture may be present, with amblyopia in some. Some children experience diplopia on gaze in elevation and adduction of the affected eye; however, it is not usually apparent in congenital cases due to intrinsic suppression. Children may also present with supranasal orbital pain as well as signs of inflammation including sinusitis symptoms, tenderness, and joint pain.
10.2.2 Physical Examination
The hallmark of Brown’s syndrome is limited elevation in adduction when the head is upright. SO movement can be numerically quantified from minimal (–1) to severe limitations in elevation (–4). Severe, –4, is also termed Brown’s plus disease. 5 In most stages, there may be minimal hypotropia in primary position and significant hypotropia in upgaze, especially in the adducted position of the involved eye. In severe cases, vertical deviations in primary position can exceed 10 to 12 prism diopters, resulting in significant diplopia in primary position with torticollis and a chin up head posture. 5
Also present are divergence in upgaze, widening of palpebral fissures in affected eye on adduction, torticollis, anomalous eye movements in side gaze, and normal or near normal elevation in abduction. Compensatory mechanisms are instinctively maneuvered in order to avoid the hypotropia that increases in upgaze and contralateral gaze. 6 The contralateral eye’s inferior oblique (IO) muscle overcompensates for the affected SO. Increased innervation to the contralateral IO accounts for the muscle’s overaction and persists until the SO restriction is released. 7
Minimal or no elevation in adduction is present during duction testing, and forced duction testing is highly positive in the same direction. 4 Forced duction restriction is worse with retropulsion, which differentiates this from inferior rectus restriction. 8 Some duction exams may reveal an audible or palpable superior nasal click during globe up and in rotation. 5 Pain may or may not accompany movement. Positive duction tests do not firmly establish the etiology of Brown’s syndrome, as direct and indirect causes can yield similar exam results.
During ocular elevation, fundus exam reveals intorsion with the foveal position slightly above the optic disc (but seen under the disc with the inverted image of the indirect ophthalmoscope; see Chapter 12).
10.3 Etiology
10.3.1 Congenital
In congenital cases, restriction of eye elevation upon adduction is generally due to dysgenesis of the SO muscle-tendon complex, restricting the ability of the muscle to pull away from the trochlea during eye movement. 9 The mechanism by which the SO muscle moves through the trochlea explains the root of some anomalous congenital causes. In 1982, Helveston et al described that the SO central tendon telescopes to elongate the entire tendon, producing a slackening effect distal to the trochlea. 10 Some Brown’s syndrome cases may be due in part to abnormal development of the central tendon intercrossed fibers that normally permit the telescoping mechanism. 7 Video 10.1 reveals that the SO tendon may not function in a simple pulley system as initially assumed. In 1999, K. W. Wright concluded through computational models that the likelihood of an innately stiff or inelastic muscle-tendon complex provides the best-fit hypothesis for Brown’s syndrome (Video 10.1). 7
Another congenital etiology can produce similar V-pattern deviations due to mechanisms extrinsic to the SO muscle. Restriction of ocular elevation in adduction may be caused by fibrous adhesions mechanically preventing a normal SO muscle tendon from elongating properly. Fibrous adhesions may also be present throughout the inferior globe, preventing the eye from elevating appropriately, and rare cases of atypical inferior malposition of the lateral rectus may also limit eye elevation. 7
10.3.2 Acquired
Brown’s syndrome can also arise from orbital and globe trauma, surgery, sinusitis, mass effects, and inflammatory conditions such as rheumatoid arthritis and juvenile idiopathic arthritis. 9
Fibrosis or scarring may develop following trauma or surgery in and around the trochlear area or within the tendon itself. Mechanical restriction from iatrogenic causes is relatively uncommon but can be so severe as to restrict both shortening and lengthening tendon movement, producing a Brown syndrome superimposed on an SO palsy.
Hindered telescoping elongation, tight muscle-tendon complex, and acquired short tendons can result from masses that displace or compress the tendon, scleral buckling surgery, local edema within the trochlear space, and in rare cases, acquired fibrosis due to thyroid disease or Hurler-Scheie syndrome.
SO click syndrome is seen in inflammatory conditions that produce nodules or thickened regions on the SO tendon causing difficulty in entering the trochlea. A palpable or audible click may be produced as the nodule is forced through the small trochlear area, restricting tendon movement. Click syndrome is associated with rheumatoid arthritis, tenosynovitis, chronic sinusitis, and systemic lupus erythematosus, as well as neoplasms and other abnormal growths directly on the tendon or tendon sheath. 11
Fibrous adhesions due to inferior or posterior orbital trauma, superior nasal orbital masses, orbital fat adhesions, and inferior rectus entrapment following orbital floor fractures may mimic Brown’s syndrome.
10.4 Differential Diagnoses
Table 10‑1 summarizes clinical features of Brown’s syndrome in comparison to two important differential diagnoses that present with similar findings.
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
