eMedicine Specialties > Ophthalmology > Extraocular Muscles

Brown Syndrome

Kenneth W Wright, MD, Director, Wright Foundation for Pediatric Ophthalmology and Strabismus; Director, Pediatric Ophthalmology Research and Education, Cedars-Sinai Medical Center; Clinical Professor of Ophthalmology, University of Southern California Keck School of Medicine
Maria Gabriela Salvador, MD, Consulting Staff, Department of Ophthalmology, Division of Pediatric Ophthalmology and Strabismus, Colonia Polanco Chapultepec Morales
Contributor Information and Disclosures

Updated: Dec 3, 2007

Introduction

Background

In 1950, Harold W. Brown first published on an unusual motility disorder, characterized by the following: limited elevation in adduction; divergence in straight upgaze (V-pattern); same degree of limitation on versions, ductions, and forced ductions; widening of the palpebral fissure on adduction; normal or near normal elevation in abduction; restricted forced ductions to elevation in adduction; and compensatory chin elevation for binocular fusion.

Brown attributed the limited elevation to a short or tight anterior superior oblique tendon sheath. He termed this as superior oblique tendon sheath syndrome. The syndrome could be acquired or intermittent. In some cases, spontaneous resolution may occur. He further hypothesized that the short tendon sheath was due to a complete congenital paresis of the ipsilateral inferior oblique muscle and secondary to sheath contracture.

In the early 1970s, Brown redefined the sheath syndrome with the following divisions: true sheath syndrome characterized only those cases that have a congenital short anterior sheath of the superior oblique tendon, and simulated sheath syndrome characterized all cases with the clinical features of a sheath syndrome caused by an anomaly other than a congenital short anterior sheath of the superior oblique tendon.¹ Clinical features of true and simulated sheath syndromes were similar, but true sheath syndrome was always congenital and constant without spontaneous recovery.

In the mid 1970s, Parks and colleagues reported that a tight tendon sheath was not the cause of Brown syndrome; instead, it was a tight or short superior oblique tendon.² Subsequent studies confirmed the cause of the syndrome to be a tight or inelastic superior oblique tendon.

Pathophysiology

Brown syndrome can be divided into congenital and acquired.

Congenital Brown syndrome

As originally demonstrated by Brown, normal elevation of the eye into adduction increases the distance between the trochlea and the superior oblique insertion as the eye moves up and into adduction. A tight or inelastic superior oblique tendon muscle complex would restrict ocular elevation in adduction. Many theories for the cause of the tight or inelastic tendon exist.

Helveston theory of abnormal telescoping mechanism

Until recently, it was believed that the superior oblique tendon moves through the trochlea much like a rope through a pulley. Through a detailed anatomical study, Helveston showed that the tendon-slackening distal to the trochlea comes from a telescoping elongation of the central tendon.³

Telescoping elongation of the tendon is due to movement of the central tendon fibers, which have scant inter-fibers connections.

Congenital Brown syndrome could be caused by a developmental abnormality of the elastic-crossed fibers that normally allow the telescoping movement of the central tendon fibers.

Wright hypothesis of congenital inelastic superior oblique muscle-tendon complex

In 1999, Wright described a computer simulation of Brown syndrome, using two specific models, as follows: (1) a short superior oblique tendon, and (2) a stiff superior oblique tendon (stretched sensitivity). The computer model showed that a tight or inelastic muscle-tendon complex was the best fit for the Brown syndrome pattern of deviation.   

The best simulation of Brown syndrome was obtained with 250% stretched sensitivity, producing a -4 limitation of elevation in adduction and a -1 limitation of elevation in abduction.  With this simulation of a stiff superior oblique muscle-tendon complex, there was a very small deviation in primary position and no deviation in downgaze, which is consistent with the clinical findings of Brown syndrome. 

Shortening the tendon from 32 mm to 28 mm did not significantly limit the elevation in adduction; however, shortening the tendon to 22 mm created a -4 limitation of elevation in adduction.  Shortening the tendon to 22 mm also caused a hypotropia of 11 prism diopters (PD) in primary position and a hypotropia of 7 PD in downgaze, which is inconsistent with the classic clinical findings of Brown syndrome, where the deviation in primary position is very small to nonexistent and there is no hypotropia in downgaze. 

Thus, the best computer model for Brown syndrome is a stiff or inelastic muscle-tendon complex. Perhaps, congenital Brown syndrome is a form of congenital fibrosis of the superior oblique muscle, which results in a stiff or inelastic muscle-tendon complex.⁴

Congenital nonsuperior oblique tendon etiology

Inferior orbital fibrous adhesions to the posterior globe would limit the eye movement. This could be caused by congenital bands.

Acquired Brown syndrome

See Causes.

Abnormal telescoping mechanism

In constant or intermittent acquired Brown syndrome, reduced telescoping elongation of the superior oblique tendon would be due to one of the following: vascular dilatation of the tendon sheath vessels and local edema occurring within the confined area of the trochlea.

Tight or inelastic superior oblique tendon

A tight superior oblique tendon can be caused by a mass that displaces the tendon, a scleral buckling, or a superior oblique tendon tuck.

A rare, acquired fibrosis of the superior oblique muscle is possibly associated with thyroid disease, an intramuscular injection of local anesthetic, or Hurler-Scheie syndrome.

Acquired short tendon

This condition could be caused by a superior oblique tendon tuck, a mass that displaces the tendon, or a scleral buckling.

Superior oblique click syndrome

This theory has been used to explain acquired Brown syndrome that is associated with inflammatory conditions.

Inflammation produces a nodule on the superior oblique tendon, just posterior to the trochlea. The nodule would have difficulty entering the trochlea, thus restricting tendon movement.

Stenosing tenosynovitis (trigger-thumb analogy theory)

Chronic movement of the superior oblique tendon through the trochlea can result in a traumatic tenosynovitis with tendon-swelling and stenosis of the surrounding tendon sheath.

Trigger-thumb is a congenital or acquired constriction or stenosis of the fibrous sheath, which surrounds the tendon and causes secondary enlargement of the tendon proximal to the constriction.

The combination of a sheath-stenosis and tendon swelling prevents movements of the tendon.

Peritrochlear scarring

Scarring or fibrosis around the trochlea and the anterior superior oblique tendon would restrict the tendon movement, causing Brown syndrome.

Extensive scarring around the trochlea can result in restriction of the tendon movement in both ways, resulting in both a Brown syndrome and a superior oblique palsy (canine tooth syndrome). This can be caused by trauma, periocular surgery, and upper lid blepharoplasty with removal of periorbital fat with cautery.

Acquired nonsuperior oblique etiologies

Inferior orbital fibrous adhesions to the posterior globe are caused by the following: orbital floor fracture and fat adherence syndrome associated with inferior orbital trauma.

Superior nasal orbital mass

These patients usually demonstrate a large vertical deviation in primary position often associated with exotropia. Possible causes are a glaucoma drainage implant or a neoplasm in the superior orbital quadrant.

Frequency

United States

Frequency of this condition is 1 in 400-450 strabismus cases.

Although familial Brown syndrome appears to be rare, Wright showed that 35% of patients with congenital Brown syndrome had a family member with amblyopia or strabismus.⁴ This finding might indicate the presence of an underlying genetic trait.

International

Same as in the United States.

Mortality/Morbidity

Amblyopia, strabismus, and an abnormal head position may be findings from Brown syndrome.

Race

No racial predilection exists.

Sex

In Brown's classic study of 126 patients, he reported that there was a higher incidence of the syndrome in females (59%) than in males (41%). A right-eye bias also occurred; involvement was 55% in right eyes, 35% in left eyes, and 10% bilateral.

Wright found 5% of bilateral cases and analyzed the male-female distribution of Brown syndrome according to different subgroups: congenital Brown syndrome (almost identical sex distribution), idiopathic acquired Brown syndrome (63% females), and traumatic acquired Brown syndrome (82% males).⁴

Clinical

History

• Diplopia may occur when the patient looks up and to the contralateral side of the affected eye.
  • Patients with congenital Brown syndrome rarely complain of diplopia, because most patients have developed suppression.
  • Patients with acquired Brown syndrome in late childhood or adulthood experience diplopia when tropic.
• Pain
• Some patients with acquired Brown syndrome present with inflammatory signs.
• These signs include supranasal orbital pain, tenderness, intermittent limitation of elevation in adduction, and pain that is associated with this ocular movement.

Physical

Characteristic physical findings include the following:

• Limited elevation in adduction, an invariable sign, is the hallmark of Brown syndrome. The amount of limited elevation in adduction can range from minimal (-1) to severe (-4).  The severe form has been termed Brown plus. Even in severe cases of congenital Brown syndrome, there is minimal hypotropia in primary position and no hypotropia in downgaze. 
• A significant limitation of elevation in abduction is present in 70% of patients, but it is the difference between elevation in adduction versus elevation in abduction that differentiates Brown syndrome from such disorders as double elevator palsy (where elevation is equal to or worse in abduction).
• A lack of significant hypotropia in primary position in cases of nontraumatic Brown syndrome has been observed. In contrast, much larger hypotropias have been observed in cases of Brown syndrome associated with trauma or periorbital surgery.
• If the vertical deviation in primary position is greater than 10-12 PD, consider an inferior oblique palsy, severe periocular scarring, or a superior nasal mass; do not consider Brown syndrome caused by a tight or inelastic superior oblique tendon.
• Patients often present with compensatory head-posturing, their chin up, and a contralateral face turn to avoid the hypotropia that increases in upgaze and gaze to the contralateral side of the affected eye.
• Amblyopia can occur in patients with Brown syndrome, but the incidence compared with the general population is low in most patients with good binocular fusion.
• Minimal or no superior oblique overaction and positive forced ductions up and in are present. The presence of even mild superior oblique overaction should be regarded with suspicion, since this finding is inconsistent with Brown syndrome of superior oblique tendon etiology.
• A feature that often is associated with acquired Brown syndrome is an audible or palpable superior nasal click on ocular rotations up and nasalward; sometimes, the pain is associated with this ocular movement.
• Digital pressure in the area of the trochlea can unlock and improve ocular rotations in some cases.
• Contralateral pseudoinferior oblique overaction occurs because of the limited elevation in abduction.
  • Because of the Hering law of yoke muscles, increased innervation to the contralateral inferior oblique muscle occurs as the eye with Brown syndrome tries to elevate and abduct.
  • Apparent inferior oblique overaction disappears when the superior oblique restriction is relieved.
• The positive forced ductions maneuver is a critical part of the syndrome; it equals the limitation that is seen on ductions and versions.
• A positive forced ductions test, by itself, does not indicate a tight superior oblique muscle tendon as the cause of Brown syndrome. Nonsuperior oblique restrictions (eg, inferior orbital adhesions) can restrict ocular elevation in adduction.
• Objective fundus torsion: In Brown syndrome secondary to a tight superior oblique tendon, intorsion occurs as the eye moves up and encounters the tight superior oblique tendon. Clinically, no torsion occurs in primary position or downgaze, but intorsion in upgaze does occur.

Causes

References

• Trochlear Nerve Palsy