Purpose: To better understand the various etiologies of Brown's syndrome, define specific clinical characteristics of Brown's syndrome, describe the natural history of Brown's syndrome, and evaluate the longterm outcome of a novel surgical procedure: the silicone tendon expander. Also, to utilize a computer model to simulate the pattern of strabismus seen clinically with Brown's syndrome and manipulate the model to show potential surgical outcomes of the silicone tendon expander.
Methods: Charts were reviewed on patients with the diagnosis of Brown's syndrome seen at a children's hospital ophthalmology clinic from 1982 to 1997, or seen in the author's private practice. Objective fundus torsion was assessed in up gaze, down gaze, and primary position in 7 Brown's syndrome patients and in 4 patients with primary superior oblique overaction. A fax survey was taken of members of the American Association of Ophthalmology and Strabismus (AAPOS) listed in the 1997-1998 directory regarding their results using the silicone tendon expander procedure for the treatment of Brown's syndrome. A computer model of Brown's syndrome was created using the Orbit 1.8 program by simulating a shortened superior oblique tendon or by changing stretch sensitivity to create an inelastic muscle.
Results: A total of 96 patients were studied: 85 with Brown's syndrome (38 with congenital and 47 with acquired disease), 6 with masquerade syndromes, 1 with Brown's syndrome operated on elsewhere, and 4 with primary superior oblique overaction in the torsion study. Three original clinical observations were made: 1. Significant limitation of elevation in abduction occurs in 70% of Brown's syndrome cases surgically verified as caused by a tight superior oblique tendon. Contralateral pseudo-inferior oblique overaction is associated with limited elevation in abduction. 2. Traumatic Brown's syndrome cases have larger hypotropias than nontraumatic cases (P < .001). There was no significant hypotropia in primary position in 56 (76%) of 74 congenital and nontraumatic acquired cases despite severe limitation of elevation. 3. Of 7 patients with Brown's syndrome, 6 had no significant fundus torsion in primary position, but had significant (+2 to +3) intorsion in up gaze. Spontaneous resolution occurred in approximately 16% of acquired nontraumatic Brown's syndrome patients. The silicone tendon expander was used on 15 patients, 13 (87%) were corrected with 1 surgery and 14 (93%) with 2 surgeries. The only failure was a Brown's syndrome not caused by superior oblique pathology. Five of the silicone tendon expander patients had at least 5 years follow-up (range, 5 to 11 years). Four (80%) of the 5 patients had an excellent outcome with 1 surgery, final results graded between 9 and 10 (on a scale of 1-10, 10 is best). The fifth patient had a consecutive superior oblique paresis and a good outcome after a recession of the ipsilateral inferior oblique muscle. The AAPOS survey had a mean outcome score of 7.3, with 65% between 8 and 10. There were 9 (6%) complications reported: 4 related to scarring and 5 extrusions of the implant. Three of the 5 extrusions were reported from the same surgeon. The computer model of an inelastic superior oblique muscle-tendon complex best simulated the motility pattern of Brown's syndrome with severe limitation of elevation in adduction, mild limitation of elevation in abduction, minimal hypotropia in primary position, no superior oblique overaction, and intorsion in up gaze.
Conclusions: The presence of mild to moderate limitation of elevation in abduction is common, and its presence does not eliminate the diagnosis of Brown's syndrome. The majority of Brown's syndrome patients have a pattern of strabismus consistent with an inelastic superior oblique muscle-tendon complex that does not extend, but can contract normally; not the presence of a short tendon. The presence of inelastic or tethered superior oblique muscle-tendon can be diagnosed without forced duction testing by observing the pattern of strabismus including torsion. Because of the chance for spontaneous resolution, conservative management, not surgery, should be the first line of treatment for acquired Brown's syndrome. If surgery is indicated, a novel procedure, the silicone tendon expander, is an effective option with excellent long-term outcomes.