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Brown's syndrome
Classification and external resources
ICD-10 H50.6
ICD-9 378.61
DiseasesDB 34071

Brown syndrome is a rare eye disorder characterized by defects and errors in eye movement. Some people may be born with this disorder (congenital) or the disorder may be developed because of a pre-existing disorder. Brown syndrome is caused by malfunctions of the tendon sheath controlling eye movement. The superior oblique tendon sheath surrounds the eyeball and when it is not working properly the patient will experience Brown syndrome (strabismus). What happens is the tendon is too short, long, thick, or inflamed. This effect causes the eye to move upward. Sometimes a Brown syndrome patient will tilt their head and their chin will rise in order to feel comfortable. When this occurs their eyes roll into their original place and the person is able to see much more clearly. Brown syndrome, in the United States, is found in every 1 to 400-450 strabismus cases. A strabismus case is the inability of the eye to focus on an object because of the problems with the muscles controlling eye movement. It is proven that 35% of the patients with congenital Brown syndrome have a family member with Brown syndrome. This fact indicates Brown syndrome could potentially be a genetic trait. The syndrome occurs in women more than men. Of the people that have the syndrome in the United States 59% of them are female and 41% male. The syndrome is right eye bias; it is found 55% of the time in the right eye, 35% in the left eye, and 10% bilateral.

Contents

Background

Brown 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 changed to limited elevation in adduction from mechanical causes around the superior oblique. Meaning that when the head is upright, there is a restriction of how the eye moves because of problems with muscles and tendons that surround the eye. Harold W. Brown characterized the syndrome in many ways such as; limited elevation in the eye when head is straight up, the eyes point out in a straight up gaze; greater separation of the upper and lower eyelids when the head is straight up; near normal elevation in adduction; and chin elevation for binocular fusion, to see one clear image instead of two blurry images. These ways are the main characteristics and signs of Brown syndrome. Brown concluded that all of these features of Brown 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. He hypothesized that the short tendon sheath was because of a complete separation, congenital paresis, of the ipsilateral inferior oblique muscle and secondary to a permanent shortening.After more research Brown 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 Syndrome. The real cause was a tight or short superior oblique tendon; studies have confirmed this and have labeled the tendon inelastic.

Types

Brown syndrome can be divided in two categorizes based on the restriction of movement on the eye itself and how it affects the eye excluding the movement. The syndrome can be separated into congenital Brown syndrome or acquired Brown syndrome (Wright). Congenital is present at birth and is described as the normal elevation of the eye into adduction. Meaning when the head is straight up, adduction, the eye is in its normal position. With Brown syndrome there is an increase between the trochlea and superior oblique tendon when the eye is straight up causing the eyes to position themselves differently. Acquired may occur as a result of another pre-existing disorder or the stretching of the tendon sheath.

Congenital There are different types of congenital Brown 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 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 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 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 syndrome.

Characteristics

There are some key characteristics of Brown 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

Causes

There are a few classifications and potential causes for Brown syndrome. Congenital Brown 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 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.

Treatments

Medical Care There are a few procedures that can be done to fix Brown 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.

Surgical Care The most effective method to fix Brown 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. The Wright silicone tendon expander technique can be used to fix chin elevation during adduction, head positioned normal, by lengthening the superior oblique tendon. This is done by performing tenotomy, cutting the tendon, and then inserting a segment of medical grade silicone 240 retinal band between the cut ends of the tendon. The problem with this procedure is that the silicone has to be placed within the tendon capsule without disrupting the floor of the tendon capsule. If this is done improperly the implant could be forced out of the tendon or the implant might attach to the outside of the tendon instead of holding the two tendons together. This procedure is very effective and is most commonly used when dealing with surgical repair. A few more methods to fix Brown syndrome include: the superior oblique split tendon lengthening technique, tenotomy, and superior oblique recession. The first method, superior oblique split tendon lengthening involves splitting the tendons on the section of the eye near the nose. This is done by removing the halves of the tendon, combining them together, and then eventually joining the halves that were made one onto the old tendon. The tendons are separated in a controlled manner and the superior oblique tendon remains as its original self. The reason this isn’t used more often is because it weakens the tendon. By cutting the tendon in half and combining it, the tendon will never be its original self because the new tendon from the old halves is now longer and weaker. Tenotomy, cutting of the tendon, is done by using a 5-6mm stitching that keeps the already cut tendons from expanding too far. The main issue with this type of surgery is controlling the cut tendons from separating too far. This stitched bridge helps control the tendon but often causes under corrections. The rate of success for this procedure is 50-85%. The superior oblique recession technique creates a controlled slackening of the tendon. This is used the least compared to all of the other procedures because of its high rate of failure and chance for under corrections. More problems with this procedure include a change with the characteristics of the superior oblique tendon and possibly limited depression (Wright). Facial reconstruction is the final option to help patients with Brown Syndrome. It is not recommend or used commonly because of the difficulty of the procedure and because of its low success rate. It is uncommonly used because freeing facial restrictions is usually unsuccessful. Cases in which the patients eyes are aligned properly and in the primary position the best thing to do is absolutely nothing.

See also

External links

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