Brown's syndrome is a rare eye disorder characterized by defects and errors in eye movement. The disorder may be congenital (existing at or before birth), or secondary (for example, due to inflammation). Brown's syndrome is caused by a malfunction of the superior oblique tendon, causing the eye to have difficulty moving upward, particularly during adduction (when eye turns towards the nose).
In the United States, the prevalence of Brown's syndrome is 1 in every 400–450 strabismus cases. 35% of the patients with congenital Brown's syndrome have a family member with Brown's syndrome. This indicates Brown's syndrome could potentially be a genetic trait. The syndrome occurs in women more than men. Of the people who have the syndrome in the United States, 59% are female and 41% male. In 55% of patients the syndrome is found only in the right eye, 35% only in the left eye, and 10% bilaterally.
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Brown's syndrome was first documented by Harold W. Brown in 1950. He initially named it the "superior oblique tendon sheath syndrome". Since then, the name has changed, and the definition of the syndrome has become "limited elavation in adduction from mechanical causes around the superior oblique". This definition indicates that when the head is upright, the eye is restricted in movement due to problems with muscles and tendons that surround the eye.
Harold W. Brown characterized the syndrome in many ways such as
He concluded that all of these features of Brown's syndrome were due to the shortening or tightening of the anterior superior oblique tendon. Because this syndrome can be acquired or occur at random and has spontaneous resolution, Brown hypothesized one major truth for this disorder — that the short tendon sheath was due to a complete separation, congenital paresis, of the ipsilateral inferior oblique muscle and secondary to a permanent shortening.
After further research, he redefined the sheath syndrome into the following divisions: true sheath syndrome, which categorized only the cases that had a congenital short anterior sheath of the superior oblique tendon, and simulated sheath syndrome, which characterized all cases in which the clinical features of a sheath syndrome caused by something different other than a congenital short anterior sheath of the tendon. The clinical features of the two categories are correct but true sheath syndrome is always congenital. However, in 1970 it was discovered that a tight sheath tendon was not the cause of Brown's Syndrome. The real cause was a tight or short superior oblique tendon; studies have confirmed this and have labeled the tendon inelastic.
Brown's syndrome can be divided in two categorizes based on the restriction of movement on the eye itself and how it effects the eye excluding the movement.
Present at birth. It is the normal elevation of the eye into adduction, such that when the head is upright, adduction, the eye is in its normal position. With Brown's Syndrome, there is an increase between the trochlea and the superior oblique tendon when the eye is straight up, causing them to position themselves differently.
There are different types of congenital Brown's Syndrome within each class. The first one, Halveston’s theory of abnormal telescoping, forced, mechanism, is described as the tendon-slackening from its center attachment to the trochlea comes from a forced stretching of the central tendon. The stretching of the central tendon is mainly caused by the movement of the central tendon fibers.
Another theory is the Wright hypothesis of congenital inelastic superior oblique muscle-tendon complex. This theory found that a tight or inelastic muscle-tendon complex was the best situation for a Brown's Syndrome patient. If the tendon was stretched about 250% there was a drop in elevation and the syndrome could be cured. Another fact from this experiment was that the attachment of the inferior orbital fibrous to the posterior glove would restrict eye movement.
Acquired Brown's Syndrome (Wright) may occur as a result of another pre-existing disorder or the stretching of the tendon sheath.
Abnormal forcing mechanism explains a reduced lengthening of the superior oblique tendon is caused by stretching of the tendon sheath. Tight or inelastic superior oblique tendon describes how a tight superior oblique tendon can be caused. It is caused by a displacement of the tendon or a superior oblique tendon tuck. However, tissue built up around the superior oblique tendon could be a sign of thyroid disease or Hurler-Sheie syndrome.
Brown's Syndrome patients who have inflammatory conditions are described as having superior oblique click syndrome. Stenosing tenosynovitis or the trigger-thumb analogy theory is the most detailed theory for all acquired theories. In this theory the frequent movement of the superior oblique tendon can result in tendon swelling surrounding the tendon sheath. Scarring occurs around the trochlea because the anterior superior oblique tendon has limited movement causing Brown
There are some key characteristics of Brown's syndrome that are not just obvious but also a disadvantage for the person. The first sign is when the chin points up and to the opposite side of the eye with the disorder. Another sign is when the head is straight up, the eye with the disorder is not aligned correctly in the eye socket, and is usually pointed at the nose because of the problems with the superior tendon sheath.
Some other ones that are not so common and mentioned are; the eye does not move up in a straight up gaze, greater separation of the upper and lower eyelids when the head is straight up, the eye may be down shot when involved in adduction, there may also be some pain for the person with the syndrome. These characteristics are clear because they are on the outside of the body, which also makes them disturbing to the unknown.
There are a few classifications and potential causes for Brown's syndrome. Congenital Brown's Syndrome could be caused by an inelastic muscle-tendon complex, differences of the superior oblique tendon fibers, abnormal inferior orbital attachments, and the posterior orbital bands.
Brown's syndrome has been researched more because it can be developed due to other diseases and disorders. A cause for scarring and adhesions is because during surgery you can receive scars from having a blepharoplasty, plastic surgery on the eye lid, and having fat removed. Reasons for the tightening or shortening of the superior oblique tendon are because of the muscles surrounding the tendon. An inelastic muscle would cause the tendon to shorten because its inflexible characteristic or a superior oblique tuck would because there is a section of the tendon removed.
There are a few procedures that can be done to fix Brown's syndrome medically. When treating Brown syndrome with medical care the goal is to release the mechanical limitation to elevation in the eye. This can be solved by using anti-inflammatory medication. One approach is with ibuprofen. Another way to do this is to inject a steroid into the trochlea and oral corticosteroids. This is done because the trochlea and oral corticosteroids tend to limit movement and cause inflammation.
The most effective method to fix Brown's syndrome is by the use of surgical care. The most important indication for surgery is the presence of chin elevation or the eye not being positioned in its normal place when the head is straight up and down.
A few more methods to fix Brown's syndrome include: the superior oblique split tendon lengthening technique, tenotomy, and superior oblique recession.
All procedures aim to align patients' eyes properly when they are in the primary position — the ideal state.