Brown syndrome is a rare form of strabismus characterized by limited elevation of the affected eye. The disorder may be congenital(existing at or before birth), or acquired. Brown syndrome is caused by a malfunction of the Superior oblique muscle, causing the eye to have difficulty moving up, particularly during adduction (when eye turns towards the nose). Harold W. Brown first described the disorder in 1950 and initially named it the “superior oblique tendon sheath syndrome”.
A simple definition of the syndrome is “limited elevation 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:
- Limited elevation in the eye when head is straight up
- Eyes point out in a straight up gaze (divergence in up gaze)
- Widening of the eyelids in the affected eye on adduction
- Head tilts backwards (compensatory chin elevation to avoid double vision)
- Near normal elevation in abduction
He 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 — that the short tendon sheath was due to a complete separation, congenital paresis, of the ipsilateral (on the same side) 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.