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 Browns Syndrome. The real cause was a tight or short superior oblique tendon; studies have confirmed this and have labeled the tendon inelastic. Causes
Browns syndrome can be divided in two categories based on the restriction of movement on the eye itself and how it affects the eye excluding the movement:
Congenital (present at birth) Browns syndrome results from structural anomalies other than a short tendon sheath but other fibrous adhesions may be present around the trochlear area. Acquired cases arise from trauma, surgery, sinusitis and inflammation of the superior oblique tendon sheath in rheumatoid arthritis.
Ankylosis is a stiffness of a joint due to abnormal adhesion and rigidity of the bones of the joint, which may be the result of injury or disease. The rigidity may be complete or partial and may be due to inflammation of the tendinous or muscular structures outside the joint or of the tissues of the joint itself.When the structures outside the joint are affected, the term "false ankylosis" has been used in contradistinction to "true ankylosis", in which the disease is within the joint. When inflammation has caused the joint-ends of the bones to be fused together, the ankylosis is termed osseous or complete and is an instance of synostosis. Excision of a completely ankylosed shoulder or elbow may restore free mobility and usefulness to the limb. "Ankylosis"  is also used as an anatomical term, bones being said to ankylose (or anchylose) when, from being originally distinct, they coalesce, or become so joined that no motion can take place between them.The term is from Greek ἀγκύλος, bent, crooked. Causes
Ankylosing spondylitis is a type of arthritis in which there is long-term inflammation of the joints of the spine. Other forms of arthritis may sometimes also lead to ankylosis, including rheumatoid arthritis and reactive arthritis
Osteoarthritis usually confers osteophyte formation, which may eventually fuse across joints. Osteoarthritis is believed to be caused by mechanical stress on the joint and low-grade inflammatory processes. Arthrodesis is the intentional creation of ankylosis in a joint.