Brown syndrome (orbit)

Brown syndrome refers to a failure of upward gaze while the eye is adducted secondary to an abnormality of the superior oblique tendon sheath complex.

Pathophysiology

This abnormality is a little counter-intuitive and highlights how the action of the superior oblique is position-dependent and that eye movement is dependent on the coordinated action of multiple muscles.

During abduction, it depresses the eye (down-gaze) whereas in adduction it causes intorsion (inward torsion). However, for the eye to be able to look upwards in adduction, a motion carried out by contraction of the inferior oblique muscle, free motion of the superior oblique tendon complex through the trochlea needs to be able to occur. Thus abnormalities at this level prevent the eye from gazing upwards, restricting its motion ^1-3. 

Causes :

Brown syndrome (orbit) can be congenital or acquired.

Congenital causes: Congenital anomalies of the superior oblique–trochlea complex.

Acquired causes: Mass, sinusitis, trauma, juvenile idiopathic arthritis, SLE, thyroid-associated ophthalmopathy, neuromuscular junction disease, myopathies, surgery and local inflammation.

Laboratory tests:

The following laboratory tests can be helpful in determining the cause of the syndrome.

Rheumatoid factor, anti-nuclear antibody, ESR,  CRP, Acetylcholine receptor antibody, anti-muscle-specific kinase antibody, TSH and FREE-T4.

Radiological findings:

MRI is the best modality to diagnose Brown's syndrome.

MRI findings include thickening and significant enhancement surrounding the left superior oblique tendon trochlear complex.

History and etymology

It was first described by Allan Brown in 1950 ¹.

See also

• Brown-Sequard syndrome
• Parinaud sydrome